* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download iiiiiiiiii - Cancer Research
Immune system wikipedia , lookup
Molecular mimicry wikipedia , lookup
Lymphopoiesis wikipedia , lookup
Monoclonal antibody wikipedia , lookup
Adaptive immune system wikipedia , lookup
Psychoneuroimmunology wikipedia , lookup
Polyclonal B cell response wikipedia , lookup
Innate immune system wikipedia , lookup
Immunosuppressive drug wikipedia , lookup
AGGLUTINATION TESTS IN THE STUDY OF TUMOUR IMMUNITY, NATURAL AND ACQUIRED THOMAS LUMSDEN, M.D. Director of Cancer Research, London Hospital In 1898 Bordet (1) recorded the fact that an animal immunised against red blood cells from a different species developed in its serum lysins and agglutinins more or less specific to the red cells used as an antigen. Two years later Ehrlich and Morgenroth (2), working with goats, showed that even the inoculation of homologous red cells in some cases evoked haernolysins (Isolysins ). Todd and White carried these investigations further and in TAIlLE I: Correlating the Various Antibodies Toxic to Cells and Showing Their Nomenclature Cytotoxins I I I I Surface cytoplasmic antibodies ,_I, Ixo- I I I Cyto- or Chromato, Iysins Agglutinins H aemolysins I Ietero- Nuclear antibodies I I I Hetero- Iso- Species I I_I, Iso- ------ I I for Nucleated cells Cell agglutinins for Blood celts I Inemagglut i nl ns I Hetero- Auto(autospermatoxi ns) Iso-agalutinins ~I Hetero- I Antispecies bodies \ Non-species specific I lIeterocytotoxic (heterotoxins) Homo- I Hornocytotoxic (homotoxins) When nucleated homologous cells are used as an antigen, the surface and the nuclear antibodies (agglutinins and chromatolysins) run roughly parallel. 1910 (3) discovered that in oxen isolysins varied in their haemolytic effect on the red cells of different individuals; in short no two isolytic sera were absolutely alike, their characters depending upon two factors: (a) the individuality of the injected corpuscles; (b) the individuality of the animal into which they are injected. By absorption of polyvalent sera, Todd and White were able to identify the cells of any individual ox. Later (1930) Todd (4) in an important paper confirmed in fowls the results obtained in oxen, having found that by means of simple immunity reactions he could differentiate the red corpuscles of any particular fowls which were not close blood relations. The experiments described below show that in normal rats the agglutinability of the red blood corpuscles varies widely, and that a high degree of agglutinin sensitivity is characteristic of certain individual rats not necessarily of any particular breed or group. 395 396 THOMAS LUMSDEN The reactions of a number of sera of rats immunised against various normal and malignant tissues with readily agglutinable rat red blood cells have also been investigated, and are considered in the light of results previously recorded (5, 6, 7). The various antibodies toxic to cells are tabulated, and the nomenclature used in this paper is given, in Table 1. METHODS Sera are obtained from a few drops of blood drawn into fine glass tubules from the tails of the rats under investigation. One end of each tubule is sealed and after centrifugation the portion of the tubule containing the serum is cut off with a diamond. In order to obtain a suitable suspension of red blood cells, a counted number of drops of blood from a glass tubule (1. 5 mm. in diameter) are run directly into a glass centrifuge tube containing about three times as much citrated saline. The cells are washed three times with saline and centrifuged practically dry; as many drops of saline as there were originally of blood are added and, after agitation, a sample is examined in the serum of the rat from which the cells came in order to ascertain that it is entirely free from cell clumps. There is a good deal of variation in the ease with which a completely homogeneous dispersion of cells can be obtained, and in some instances it may be found best to avoid the saline washings and the repeated centrifugation thus entailed. Indeed; saline washing has been found to be not really essential, although it was done in the experiments recorded. The drop of the serum under investigation is run from the tubule on to a grease-free cover slip, an appropriate amount (about a quarter of a drop) of citrated red blood cells is added from a very fine capillary tube and is intimately intermixed with the serum. The cover slip is then inverted over a hollow slide and sealed with paraffin. It will be seen that there is little dilution of the serum and all the tests are therefore roughly comparable. The hanging drop preparations are placed in a thermostat at 37 0 for twenty minutes or are left at laboratory temperature for two to three hours. Thereafter the agglutination, if any, is estimated, first with the naked eye, the slide being tilted gently so that the corpuscles flow from side to side. In the presence of macroscopic agglutination the corpuscles do not flow freely, but tend to form a mass sharply demarcated from the serum. The hand holding the slide (now turned face downwards) is then made to describe a circle, ten or twelve times, as rapidly as may be without swinging off the drop, and the titre of agglutination is estimated microscopically, with a % inch objective. The results are tabulated in accordance with the following scale. In recording these, wherever doubt existed as to the degree of agglutination the lower estimate was assigned. (1) (2) (3) (4) (5) +++ ++ ± ++ + ++ .. . Complete agglutination; no free red corpuscles seen, all being aggregated in very large masses. .No free red blood corpuscles; clumps smaller but still large. ... Some free red blood corpuscles now seen, between large clumps. .. A halfway stage between (3) and (5). . .Agglutinated masses just visible to the naked eye. AGGLUTINATION TESTS IN STUDY OF TUMOUR IMMUNITY (6) ± (7) ;t (8) :;l; (9) 0 397 .. The coarsest agglutination not visible to the naked eye. ... Clumps small though definite, consisting of 10 to SO corpuscles or thereabouts. .Unusually marked rouleau formation with few if any true clumps. Complete absence of agglutinative effect when compared with the same suspension of cells mixed with autogenous serum. The sera should be free from haemoglobin as its presence may cause slight clumping in the absence of agglutinins. "Milky" sera are also useless, since they sometimes give rise to haemolysis masking any agglutination which may have taken place. The use of the author's tissue culture table (8) greatly facilitates the performance of these tests. All the highly immunised rat sera were produced by weekly or fortnightly intraperitoneal injections of 1 c.c. of the antigen named and these inoculations were repeated at least five, and in some cases fifteen to twenty, times. In order to repeat or to extend these experiments, it is necessary to find a rat or rats with readily agglutinable corpuscles (see below). To do this, immunise several tumourresistant (non-take) rats by repeated weekly intraperitoneal inoculations of 1 C.c. of Jensen rat sarcoma (J. R. S.) fragments for two months. Draw some blood from the tails of these rats; the sera are certain to contain agglutinins, as are the sera of rats highly immunised against rat spleen. Prepare washed red blood corpuscles, using the technique already described. Test the sera of these immunised rats against the washed red cells from 20 to 30 normal male rats of various breeds (other than pure albino Wistar rats). Table V shows that it should not be difficult to find a few suitable rats. Once found, such rats can be used indefinitely for the supply of the necessary agglutinin-sensitive corpuscles. Since the agglutinability of the red blood corpuscles of different agglutininsensitive rats may vary slightly in degree in the response to particular immune sera (Table XVI), it is best in any series of experiments to use the same individual rat as the source of the corpuscles to be used as a test reagent. In the following experiments the corpuscles were always taken from an agglutininsensitive cream hooded rat, marked R. S., except where otherwise stated. As mentioned below, agglutinins always appear in the sera of rats in which a tumour implant regresses, but in some cases the agglutinins never reach a high titre and may be demonstrable only for a few days. It is therefore essential that daily examinations be made in such experiments. EXPERIMENTAL OBSERVATIONS (1) The question under investigation when the observation (Table IV) which proved to be the source of this paper was made, was whether the sera of rats immunised against normal or malignant homologous cells were isohaemolytic. Table II shows the results in one of many experiments which invariably agreed in indicating that isohaemolysins are not present in the sera of rats immunised against Jensen rat sarcoma, rat spleen, rat testis, or rat blood corpuscles. In fact, so far as the evidence goes it seems that rats are incapable of forming isohaemolysins. Table III demonstrates that there is no haemolysis in vitro, even when red corpuscles highly sensitive to iso-agglutinins (see below) are concerned. TABLE II: One of Many Experiments Showing Absence of Iso-haemolysins in Rats Serum of Rat Immune to ].R.S. Red Blood Cel1s of Normal Rat Diluted 1 in 20 with Saline Guinea-pig Serum Diluted 1 in.5 with Saline R.C. 17: 1 part 17: 1 part B.C. 17: 1 part Saline control: 1 part Normal serum control: 1 part 1 part 1 part 1 part 1 part 1 part 1 part 1 part 1 part 1 part 1 part t.c. TABLE Haernolysis o o o () o Ill: Showing that Sera of Rats Immunised against Various Homologous Tissues Agglutinate but Do Not Lyse the Red Blood Corpuscles of Agglutinin-sensitive Rats Washed Red Corpuscles of AgRlutininsensitive Rat, R.S. (I in 3 of Saline) 1. RR.Cs. 1 part 2. R.B.Cs. 1 part 3. R.B.Cs. 1 part 4. R.B.Cs. 1 part 5. R.B.Cs. 1 part 6. R.B.Cs. I part 7. R.B.Cs. 1 part 8. R.B.Cs. 1 part 9. R.B.Cs. 1 part TABLE Rat Serum Complement ].R.S.-immune rat, R.C. 2 parts J,R.S.-immune rat, R.C. 2 parts ].R.S.-immune rat, LC. 2 parts J, R.S.-immune rat, B.C. 2 parts J,R.S.-immune rat, R.S. 2 parts Rat-blood-immune rat, R.C. 2 parts Rat-blood-immune rat, r..c, 2 parts Normal rat 2 parts None None Guinea-pig serum 1 part Guinea-pig serum 1 part Guinea-pig serum I part Guinea-pig serum 1 part Guinea-pig serum 1 part Guinea-pig serum 1 part Guinea-pig serum I part Guinea-pig serum 1 part Agglutination Haemolysis +++ +++ +++ ++ +++ ++ + o 0 o 0 0 0 0 ± 0 + 0 ._- IV: Recording the Experiment in Which It Was Revealed. that the Red Blood Corpuscles of a Certain Indioidua! Rat Had an Agglutilzin Sensitivity Far Above the Average Breed of Rat from Which Washed Cells Were Taken 1. Fawn 2. Black 3. 4. 5. 6. Agouti Cream Stone Stone Hooded 7. Cream Hooded 8. Agouti Hooded 9. Fawn Hooded Serum of ].R.S.-immune Rat, R.C., 19th Serum of ].R.S.-immune Rat, R.C.L.S., 18th Lysis AgRlutination Lysis Agghitination o o o o o o o o o o o o o +++ o o o o o o o 398 o o o o o o o () o o o () +++ () o AGGLUTINATION TESTS IN STUDY OF TUMOUR IMMUNITY TABLE Breed Cream Hooded Males 1 R.S. 2 3 4 5 6 R.C. 7 L.C. Cream Hooded Females I 2 3 4 5 6 7 8 9 10 11 12 Fawn Males I 2 L.S. 3 U. 4 5 L.C. 6R.C. 7 Fawn Females I 2 3 4 B.S. 5 6 R.S. 7 8 9 10 11 12 399 V: Assay of the Agglutinability of the Red Blood Corpuscles of 187 Rats of 12 Breeds." Result +++ 0 0 0 0 + + ± 0 0 0 0 0 0 0 0 0 0 0 0 +++ ± 0 + +++ 0 0 0 0 + 0 + 0 0 0 0 0 0 Breed Black Males 1 2 3 L.S. 4 5 L.C. 6 R.C. 7 Black Females t R.S. 2 L.S. 3 B.S. 4 5 6 7 8 9 10 11 12 Stone Hooded Males IU. 2 B.S. 3L.S. Stone Hooded Females I 2 3 4 Fawn Hooded Males I 2 3 4 5 6 7 Result 0 0 + 0 + ++ 0 ++ + ± 0 0 0 0 0 0 0 0 0 0 +++ 0 0 0 0 0 Breed Agouti Hooded Males 1 2 3 4 5 R.C. 6 L.C. 7 + 0 0 0 0 0 + +++ 0 Stone Males 1 2 3 0 0 0 Cream Males 1 2 3 0 0 0 Agouti Males I L.S. 2 3 LISTER Males and Females I 2 3 4 5 6 7 8 9 10 11 0 0 0 0 0 Result 12 13 14 15 16 17 18 19 + 0 0 0 0 0 0 0 0 0 + 0 0 0 0 0 0 0 0 0 0 0 Breed LISTER (cont.) 20 21 22 23 24, 25 26 27 28 29 30 31 32 33 34 35 36 LONDON LISTER Males and Females 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 Result Breed Result LONDON LISTER ± 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 ± 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 + (cont.) 28 29 30 31 32 33 34 35 36 WISTAR Males and Females 1 2 3 4 5 6 7 S 9 10 II 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 0 0 ± 0 0 0 0 0 ± 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 • In this table titres lower than ± were disregarded since the only object of the experiment was to find rats in which the red cells were exceptionally sensitive to agglutinins. (2) In order to determine whether there were different blood groups in rats which might be important in relation to the existence of isohaemolysins, the sera and corpuscles of 28 normal rats of twelve different breeds were tested in batches of 6, 6, 6, 6, and 4, and each against each (180 separate tests). In not one instance did the serum of a normal rat cause agglutination of the red blood corpuscles of any other normal rat. It seems, therefore, that there are no characteristic blood groups in rats. (3) Although normal rat sera never agglutinate rat red cells, it was thought worth while to see whether the sera of rats immunised against Jensen sarcoma would do so. This investigation produced some unexpected results. In the first experiment the sera of two rats immune to Jensen sarcoma were each separately mixed with the washed corpuscles of nine normal rats, each of a different breed. Table IV shows that, while lysis did not occur in any of the tests, agglutination was complete in the case of the corpuscles of rat no. 7, i.e. male cream hooded rat (R. S.), while it was entirely absent in the 8 other rats, with both the immune sera tested. 400 THOMAS LUMSDEN TABLE VI: Showing tha; Over a Period of Four Months the Degree of Agglutinin Sensitivity of the Red Blood Corpuscles of the Individual RaJs Named Was Practically Constant Serum of R.C. 19th, Applied Aug. 25, '37: Agglutination Resulting Red Blood Corpuscles of MALES R.S. Cream Hooded R.C. Fawn L.S. Fawn R.C. Black L.S. Black R.C. Agouti Hooded L.C. Agouti Hooded B.S. Stone Hooded FEMALES L.S. Black R.S. Black Same Serum; Same R.B.C.: Results Oct. 29, '37 Same Serum; Same R.B.C.: Results Dec. 12, '37 +++ ++± +++ ++ + + +++ +++ ± + +++ +++ ++± ++ +± dead +++ +++ +++ +++ +++ ++ + + +++ +++ + ++ + + TABLE VII: Showing Inheruance of Agglutinin Sensitivity Titre of Agglutinogens in the Red Blood Corpuscles of Offspring (Born Nov. 1, '37) of R.S. Cream Hooded Agglutinin-sensitive Male Rat Date (1937) Nov. 14 Nov. 26 Dec. 7 Dec. 28 R.e. Male ++ ++ ++± ++± B.C. Male 0 ++± ++± ++± L.S. Male ++ ++ ++± ++± B.S. L.C. R.C.L.S. L.e.R.S. R.S. Male Female Female Female Female 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Offspring (Born Nov. 27, '37) of Stone Hooded Agglutininsensitive Male Rat Offspring (Born Nov. 7, '37) of Fawn Male Agglutinin-sensitive Male Rat Date Nov. 14 Nov. 26 Dec. 12 Dec. 28 R.e. Male L.e. Male B.C. Male ++± ++± ++± ++± +± ++ ++± ++± ++± ++± ++± ++± L.S. Male 0 0 0 0 R.S. R.C. L.e. Female Male 0 0 0 0 ++ 0 0 ++ B.e. ± ++ (4) In order to determine whether this isoagglutinability was characteristic of this particular breed of rat, the corpuscles of six other male and twelve female cream hooded rats were tested, giving the results shown in Table V. It will be seen that in two of the males (R. C. and L. C.) other than R. S. the corpuscles were agglutinated definitely though not completely, while only one of the twelve specimens from females showed feeble agglutination. It is clear that in this breed agglutinability is an individual and not an invariable racial characteristic; it appears to be more usual in males than in females. To ascertain the frequency of agglutinin sensitivity in the red blood corpus- 401 AGGLUTINATION TESTS IN STUDY OF TUMOUR IMMUNITY TABLE VIII: Recording a Number of Indiflidual Experiments and Showing That in Rats Immunised against Homologous Nudeated Tissues the TitHS of Chromatolysins and of Agglutinins Run Roughly Parallel. This is Not So When Non-nucleated Cells (Red Blood Corpuscles) Are the Antigen Rats Degree of Degree of Percentage Agglutination Agglutiof ].R.S. of Agglutinin- nation of Cells sensitive Ordinary Rat Unselected Killed R.B.Cs. Rat R.B.Cs. Rats 1 2 3 4 5 6 7 8 Anti-Rat-Testis Rats 30 +++ 20 ++± 15 +++ 15 ++± 10 + 2 + ± 2 0 ± 0 0 0 0 0 0 0 0 1 2 3 4 5 6 7 8 9 10 Anti-Rat-Blood Rats 5 +++ 2 +± 2 0 1 +++ 0 1 0 +++ 0 +++ 0 +± 0 ± 0 ± 0 0 0 0 0 0 0 0 0 0 l.R.S. Immune Rats 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 80 70 70 35 30 30 30 25 20 20 20 20 15 15 10 10 5 5 5 2 1 0 +++ +++ +++ +++ +++ +++ ++± ++± ++± ++± ++± ++± ++± ++ +± +± +± +± + +± ± 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Degree of Degree of Percentage Agglutination Agglutiof ].R.S. of Agglutinin- nation of Cells sensitive Ordinary Rat Unselected Killed R.B.Cs. Rat R.B.Cs. cles of rats, over 200 individuals of various breeds were examined in addition to those mentioned above. Most of the results are shown in Table VI but since this table was made during a search for rats with very highly agglutininsensitive red blood corpuscles, degrees of agglutination under ± are not recorded. Agglutinability of a grade below this is relatively common, and is by no means unimportant (Tables XX-XXII). While the degree of sensitivity to iso-agglutinins certainly varies from individual rat to rat, agglutinability will be seen to be commoner in some breeds than in others. Not one of the 36 Wistar rats tested showed this reaction in marked degree and it is comparatively rare in Lister Institute and London Hospital black and white rats. The numbers tested do not allow any reliable comparison to be made in the male rats of the other breeds which were tested. Iso-agglutinin sensitivity continues unaltered in degree certainly for four months (see Table VI) and possibly during life. This constancy is fortunate, since once a rat with agglutinin-sensitive red cells is found its corpuscles can be used as a test reagent for the presence and titre of agglutinins in any number of experiments. (5) Iso-agglutinin sensitivity appears to. be markedly hereditary for, as may be seen from Table VII, of sixteen young rats bred from three agglutinin- 402 TABLE THOMAS LUMSDEN IX; Showing That, When the Highest Titre of Iso-agglutinins and of Chromatolysins Observed in the Course of Many Examinations of the Sera of the Immune Rats Named Are Compared, They Run Roughly Parallel Except When Non-nucleated Cells (Blood Corpuscles) Are Used as the Antigen Sera of Rats Immune to ].RS. Highest Titre of Chromatolysins Highest Titre of Agglutinins (+++ =100%) Sera of Rats Immune to Rat Spleen Highest Titre of Chrornatolysins Highest Titre of Agglutinins RC. 19 I..C. 18 L.C. 19 RS. 19 I..S.R.C.18 B.C. 18 R.C.18 B.C. 19 90 90 90 70 65 60 50 40 +++ +++ +++ +++ +++ +++ +++ +++ I..S. B.C. R.S. I..C. R.C. 80 70 35 10 15 +++ +++ +++ ++± ++ Average 69 3 Average 42 2.7 Sera of Rats Immune to Rat Testis Highest Titre of Chromatolysing Highest Titre of Agglutinins Sera of Rats Immune to Rat Blood Highest Titre of Chromatolysins Highest Titre of Agglutinins L.e.e. RC.C. RC.I.. L.e.I.. 60 50 10 5 +++ ++± + ± I..e.C.H. I..C.L. R.e.B. +++ +± R.C.L. L.e.B. 5 5 2 2 2 1 Average 2.8 Average 31 1.75 n.c.c.a. 0 ± +++ ± Sera of Rats Immune to Rat Serum Highest Titre of Chromatol ysins Highest Titre of Agglutinins n.c.c.n. o o o o o o o o o o o o L.C.C.H. RC.F. L.C.F. RC.B. L.e.B. 1.4 sensitive males and females of corresponding breed in which agglutinability was less marked, eight have highly agglutinable red blood corpuscles. (6) Tables VIII and IX show that the red corpuscles of the agglutininsensitive rat (R. S. cream hooded) were agglutinated not only by the particular immune sera originally tested (see Table IV), but by the serum of every rat which had been immunised against homologous nucleated cells, whether normal (spleen, testis) or malignant (Jensen rat sarcoma). (7) Table VIII shows also that though these immune rat sera agglutinate the corpuscles of agglutinin-sensitive rats, they are unable to cause agglutination of the red cells of other normal rats. AGGLUTINATION TESTS IN STUDY OF TUMOUR IMMUNITY 403 (8) Table IX records the highest titre of both chromatolysins and agglutinins ever found after many tests in the particular immunised rats named. Here, as in Table VIII, it is seen that the titre of agglutinins runs closely parallel with the titre of chromatolysins, but only when the antigenic cells are nucleated. Rats immunised against rat red cells develop agglutinins, but little if any chromatolysins. (9) Comparison of the titre of agglutinins in the sera recorded in Tables VIII and IX shows that Jensen rat sarcoma, rat spleen, rat testis and rat blood may be placed in this order of efficiency as agglutinogens and in the same order as agents in the production of homocytotoxins (chromatolysins ) (8). Red cells are by no means invariably effective even as haemagglutinogens. It appears that the more invasive the type of cell, the higher its activity as an antigen. It must be noted that the correspondence between the titres of isoTABLE X: Showing That Iso-agglutinins Always Appear in the Sera of Rats in Which a Tumour Implant Regresses, but That Agglutinins Are Never Demonstrable in the Serum of a Rat in Which a Tumour is Growing Progressively (See also Tables XI-XIII) Day55 1 2 ;) 4 5 6 7 8 9 - -- 7 0 0 0 0 0 0 0 0 0 0 0 --_.- ..._ 0 ... 0 .. 0 0 0 0 - ------ --- -- -~+ 0 0 -- - - - -. -- 10 11 12 - 0 + 0 0 0 - 1~ 11 9 0 + 0 + ... .. ••• .- 0 •• 0 ++ - + - - 1++ - t+ 0 - ++ + - +t - ++ + -- ++ U-L.1..J ++t ++ +-+ ++ + -- - to --- em. 5Ca1.e 0 0 ~+~ + ++~ t,.~ + +tt + -+Ht + agglutinins and homotoxins may be somewhat obscured in sera with high titres because, when the chromatolysins reach a titre of 30 or 40 per cent, the agglutinins accompanying them are already capable of causing complete agglutination, so that above this point the rise in titre is not shown and the sera must be titrated by dilution in order to demonstrate the parallelism of the titres of the two antibodies. Further, when the homocytotoxins are undetectable-for example, long after the last injection of antigen-agglutinins may still persist in effective degree. Within reasonable limits, however, there seems no doubt that the titre of agglutinins may be taken as a rough index of the existence and amount of chromatolytic homocytotoxins, The probable reason for this parallelism is discussed later. (10) We now come to investigate whether the chromatolysins and agglutinins shown above to exist in the sera of rats immunised against homologous nucleated cells have any relation to the mechanism by which rats Ire- 404 THOMAS LUMSDEN quently resist the invasion of implanted tumour cells, as for instance when " spontaneous regression" takes place. To this end the sera of over 200 rats into which 0.1 c.c, of Jensen sarcoma fragments had been implanted were examined every two days or so from five to seven days after the implantation until the fate of the implant was certain. The results of some typical experiments are recorded in Tables X-XIlI. The most significant conclusions which may be drawn from these experiments are as follows: (a) When a tumour grows progressively, agglutinins are absent or undetectable by the methods used. TABLE XI: Agglutinins in Sera of Animals Implanted with Jensen Rat Sarcoma (See Table X) -..... -... ....-- -- ---- --- ---- -- ----- --.. -- ~aY5 5 1 2 3 4 5 6 7 8 9 10 11 12 7 9 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 6 0 0 0 - 0 0 0 0 0 - ..- •• 11 0 + 0 ++ 0 0 0 ++ 0 0 13 0 --- -- +- ++ ++ +-+ + --- -- -- 0 ttt Ht ++ Hot :I: ++ + H· + + + +++ ++ ++ ~ + + It-m. 5Cale ± --- (b) In every case when a tumour fails to grow or regresses spontaneously, at some time or other agglutinins can be demonstrated in the serum of the rat concerned. It must be insisted that frequent examinations (daily or every two days) are essential because the agglutinins may appear only for a brief period. Their titre rises, so as to be demonstrable, during or after regression, but it varies much in height in different individual rats and varies also in the length of time during which it persists, so that the occurrence of these antibodies may be overlooked if only a few examinations are made, say at weekly intervals. These findings confirm the results of cytotoxin experiments in which tissue cultures were the test material,' but the agglutination tests have the great advantage that they are easy to perform and to repeat, and the results are unmistakable and can be estimated without special training. The tissue culture experiments, on the other hand, require for their performance a considerable degree of skill and experience. While carrying out the experiments recorded above it became possible, after a time, to judge with absolute confidence from serological examination what the fate of any particular tumour implantation had been, without seeing 1 For an example of such an experiment recently published by Lumsden and Phelps (6), see Table XIV. AGGLUTINATION TESTS IN STUDY OF TUMOUR IMMUNITY 405 the rat from which the serum under investigation had been taken, and the conviction that there was a radical relation between the presence or absence of these antibodies and the fate of the tumour was forced upon the observer. (11) It had already been found in the search for blood groups that the corpuscles of the agglutinin-sensitive male rat R. S. cream hooded were not agglutinated by normal rat serum, but to make quite certain of this point the sera of 75 normal rats from twelve different breeds were mixed, as above, with the red blood corpuscles of the R. S. cream hooded male and in not one instance did agglutination take place. It is clear, therefore, that the sera of normal rats do not contain iso-agglutinins. TABLE XII: Agglutinins in Sera of Animals Implanted with Jensen Rat Sarcoma (See Table X) .. C. .. e.... ...-- .. .. -.. --.. .... 0" .. .. ... .. ..... ... pays 7 1 2 3 4 .5 6 7 8 9 10 11 12 9 11 0 0 0 0 O 0 ." 0 0 4II1II' 0 0 0 0 0 0 0 0 0 ." 0 0 0 0 0 0 0 0 0 0 ..- ---- -- 15 13 0 0 0 0 0 0 0 0 0 - + aD - - 0 ++ ± -- +± ± ± ± -- ± - ± ± ---- +t + -- ± ± --- 0 .. ----- ± +.± + + + l-L....I.-J-J ± cm.ecete + As might be expected when the sera of rats whose red blood corpuscles are agglutinin-sensitive are mixed with corpuscles of other similar rats, no agglutination takes place, and similarly the sera of rats immune to Jensen sarcoma do not agglutinate the red blood cells of other rats immune to that tumour. In other words, iso-agglutinins are not present in the sera of rats whose red blood corpuscles contain much agglutinogen, and conversely, in rats having a high titre of iso-agglutinins in their sera, agglutinogens are absent from the red blood corpuscles (Tables XVII, XX-XXIII). (12) Since the sera of rats immunised against homologous tissues (i.e. containing homotoxins) invariably agglutinate the corpuscles of agglutininsensitive rats it was of interest to determine whether the sera of rats immunised against heterologous tissues containing heterotoxins and anti-species bodies, but not homocytotoxins, would agglutinate these corpuscles. Here, as with TABLE XIII: Agglutinins in Sera of Animals Implanted with Jensen Rat Sarcoma (See Table X) .. ... .. - ... ... 9 Dcrye 1 .... 0 0 0 0 0 0 0 0 ~ 3 ... 0 0 ~ 0 0 0 0 0 1 2 ....- ........ - 4 5 • -- -...- ..- 6 7 0 0 8 0 ..... t+0 --11 -12 -- + -9 10 ~ TABLE 1~ 11 ~ ..... .. a 0 0 0 0 F • 0 0 ------ ± ++ 0 ++ 0 1: 'tt + tt 0 + -- + 0 • 0 -- ott ----em eceie 't't 0 ttt 0 ++ ~ XIV: Showing the Fate of Tumour Grafts in Ten Rats and the Results 01 Tissue Culture Tests of the Rats' Sera * 7 8 <17· 0 0 Day 6 26 -- -... 2~ <1730 31 32 33 34 0 0 ..... - .3 10 12 13 <liT. 0 0 -0 0 0 ........ .. ... ... ----...... .... .., ... 0 ~ 0 ~ 0 0 0 0 0 0 ....- -.. .. -- ..... 0 0 0 ,. lifo 0 0 0 0 0 ...- 0 0 0 t 0 1~ 570 ~c ~ 1% - .... ........ £ -- .-~ ~ 157- .....1'70 . .~70. -". 27-.'. ,. .. . 0 0 0 35 -'" 38 <1% <1% 0 37 0 * The percentage ~ 9 . - 1070 ~7a ..57- !'70 )~7. ~io " , Cm.O --- ~07a I I 5 10 4570 -:;d 1570~ • "3 m <!'70 170 • tJI <lit. 470 o' • :3 . 0 0 til · above the silhouette represents in each instance the proportion of emigrated cells killed when the serum of the rat concerned was applied to a one-day culture of J. R. s. Chromatolysins always appear at some stage when regression takes place j they are never present or are negligible in amount when a tumour grows progressively. 406 407 AGGLUTINATION TESTS IN STUDY OF TUMOUR IMMUNITY TABLE XV: Showing the Titre of Iso-agglutinins and of Chromatolysins in the Sera of Rats Immunised against Various Homologous Nucleated Cells and in the Euglobulin Fraction of the Same Redissolved in an Equivalent Volume of Normal Rat Serum Agglutination Chromatol ysis Immune Rat Sera Effect of Serum (+++=100%) Effect of Euglobulin Fraction Effect of Serum: Percentage of Cells Killed Effect of Euglobulin: Percentage of Cells Killed 1 +++ +++ +++ ++± ++ ± 0 0 0 ± - 95% 90% 80% 80% 50% 95% 90% 60% 50% 30% 2 3 4 5 XVI: Showing That There Is Some Slight Variation in the Affinity of Different Agglutinating Sera for the Particular Agglutinogens in the Red Blood Corpuscles of Certain Individual Rats T ABLE Red Blood Corpuscles of 1. R.S. Cream Hooded 2. 3. 4. 5. 6. R.C. Fawn L.S. Fawn R.c. Black L.S. Black L.S. Black (Female) Degree of Agglutination Anti-].R.S. Serum R.C. 19th ++± ++± +++ ++ ++ ± Degree of Degree of Agglutination Agglutination Anti-I.R.S. Anti-RatSerum Spleen L.C. 18th Serum B.C. + + ++ +± + ± + ± + ± ± ± Degree of Agglutination Anti-RatBlood Serum L.C.C.H. ++± ++ ++ ± 0 ± the sera of normal rats, no agglutination occurs. It appears, therefore, that these iso-agglutinins are related to homotoxins but not to heterotoxins. (13) Six rats into which 1 c.c, of cell-free rat serum was repeatedly inoculated developed neither agglutinins nor chromatolysins in their sera (Table IX). ( 14) Experiments previously recorded (5, 8) indicate that homocytotoxins exist mainly in the euglobulin fraction of sera containing them. Table XV shows that this is not so in the case of iso-agglutinins. ( 15) The question of absorption has not yet been fully investigated, but it is indicated by the experiments already carried out that agglutinins can be absorbed by either nucleated or non-nucleated cells, but that chromatolysins require nucleated cells for their absorption. It is doubtful, however, whether chromatolysins can act in the entire absence of agglutinins, and further work on this aspect is required. Among several difficulties in these experiments is the marked lability of chromatolysins, and definite conclusions cannot be drawn from a few experiments. ( 16) The experiments recorded in Table XVI suggest that there is some slight difference in the agglutinogens present in the red blood corpuscles of each particular agglutinin-sensitive rat, since there is some variation in their 408 THOMAS LUMSDEN individual affinity for particular agglutinating sera. The variation is not very great, however, and a serum which completely agglutinates the red blood corpuscles of one, agglutinates those of all agglutinin-sensitive rats. 17) In order to discover whether a rat can manufacture chromatolysins without at the same time producing haemagglutinins, a rat with agglutininsensitive corpuscles (R. C. F.) was immunised against rat spleen. As shown in Table XVII, it produced a fairly high titre of chromatolytic homocytotoxins, but its serum contained no appreciable amount of agglutinins for red blood corpuscles even of readily agglutinable variety. This observation and those at the end of Section 11, threw light upon the general question of antibody formation, which is discussed below. e XVII: Showing That When a Rat with Agglutinin-sensitille Red Blood Corpuscles Is Immunised against Rat Spleen Its Serum Contains Homotoxins but Not Haemagglutinins. When an Unselected Normal Rat Is Immunised against Rat Blood the Reverse Occurs TABLE Nonsensitive Ordinary Rat R.B.Cs. Sera Drawn Three Days After Last Immunising Inoculation of Tissue Culture of Spleen (2 day) Tissue Culture of I.R.S. (2 day) Rat spleen in agglutininsensitive rat (R.C.F.) 20 30 5 10 0 0 0 Rat spleen in ordinary non-sensitive rat 45 55 5 5 +++ +± 0 0 0 +++ +++ 0 Rat blood in ordinary rat Agglutinin-sensitive Rat R.B.Cs. R.B.Cs. R.S.C.H. Fawn L.S. (18) To determine whether the agglutinins found in the sera of rats immune to Jensen sarcoma and those immune to rat spleen were exclusively haemagglutinins or were effective also upon nucleated cells, these sera were applied to tissue cultures of rat spleen and of Jensen sarcoma. It was found that agglutination of appropriate nucleated splenic and sarcomatous cells invariably occurred if they were not so rapidly killed as to prevent clumping. It is evident that in the case of tissue cultures, agglutination of cells must take some time, since it is only when the cells migrate within each other's orbit that they are attracted to each other and adhere. If, therefore, we wish to observe agglutination of these living" cultured" cells, we must prevent rapid death of the cells either by using a weak serum or by eliminating complement, which is, of course, necessary for chromatolysis. Another fact which supports the view that the iso-agglutinins we are considering are general cell agglutinins and not solely haemagglutinins is that they are absorbed by nucleated cells (Jensen sarcoma) if anything more readily than by red blood corpuscles. It is possible that absorption of this sort may go on also if' corpore and may in part explain why, as long as an implanted tumour is growing, agglutinins are absent from the serum of the rat concerned. An observation which lends some support to this view was that in the case of three rats in which a progressively growing tumour was excised, agglutinins, previously absent, appeared in the serum, but, as might be expected, only in small amount and for a short time (Table XVIII), since, if these rats had had 409 AGGLUTINATION TESTS IN STUDY OF TUMOUR IMMUNITY XVIII: Titre of Agglutinins at Various Dates in the Sera of Three Rats from Whuh Progressively Growing Jensen Tumours Were Excised, Tested on Agglutinin-sensitive Rat Cells TABLE Dates Before excision 1 day after excision 1 week after excision 10 days after excision 2 weeks after excision Toxic effect on cultures of l.R.S. (percentage of l.R.S. cells killed) Rat R.C. Rat B.C I • Rat B.C~. 0 0 0 0 0 0 ± ± ± ± ± ± 0 0 0 2% 5% 5% much capacity to form iso-agglutinins and homotoxins, the tumours implanted into them would not have grown progressively. ( 19) The agglutinins are much more stable than the chromatolysins and when once they attain a high titre they persist in an animal's serum for a considerable number of weeks; when, however, they are formed in an unsuitable host, e.g. in a rat having some agglutinogen in its red blood corpuscles, they may be in low titre and evanescent and so may be overlooked unless daily tests are made (see Table XIII; Sections 9 and 11). The homocytotoxins are always extremely labile and are seldom if ever present in excess of the titre necessary to achieve their purpose. DISCUSSION (1) The readily agglutinable red blood corpuscles investigated in the experiments recorded above supply a convenient means of studying natural and acquired tumour immunity. The amount and nature of the agglutinogens contained in any animal's cells appear to be determined by heredity and to remain unaltered throughout life. Genetic factors in relation to cancer have been studied chiefly in America by Loeb, Little, Simpson, Bittner and many others. It has long been known that strains of mice susceptible to, and others resistant to, particular varieties of cancer could be bred, and in 1934 it was noticed (see Fig. 5 in Lumsden, Macrae and Skipper, 5) that sera of rats immune to Jensen sarcoma contained iso-agglutinins capable of clumping homologous nucleated cells. Gorer (9), however, was the first to point out the occurrence of iso-haemagglutinins in this connection and to show that in his pure strains of mice a particular variety of transplantable tumour grew progressively only in those animals whose red blood cells contained a particular antigen, whereas if this antigen was absent, the tumours regressed and isohaemagglutinins appeared. My experiments were completed before reading Gorer's paper and, in so far as Iso-haemagglutinins and agglutinogens are related to the fate of implanted tumours, there is, in principle, complete agreement between my results in unselected rats and those obtained by Gorer in his pure bred mice. (2) The Relation of Cell Agglutinins to Homocytotoxic Chromatolysins (Homotoxins): The iso-agglutinins and the homotoxins usually run parallel whether evoked by tumour implantations or by the inoculation of homologous 410 THOMAS LUMSDEN TABLE XIX: Showing Points of Difference Between Iso-agglutinins and Homoioxins Effect produced Amount in the euglobulin fraction of the serum concerned. . . . . . . . . . . . . . . .. Lability Complement. . . . . . . . . . . . . . . . . . . . . . . . . . .. Present in anti-rat-blood rat serum Present in anti-rat-spleen serum made in a rat having agglutinable red blood corpuscles. . . . . . . . . . . . . . . . . . .. Iso-agglutinins Homocytotoxic Chromatolysins Agglutination, not necessarily lethal Nucleated cells killed, chromatin lysed Little if any Very stable None needed Yes Practically all Very labile Necessary for lysis No No Yes nucleated cells (Tables VIII-IX); yet they are apparently different antibodies, for under special circumstances each can be produced separately. Thus the serum of rats immunised against rat blood cells may contain a high titre of haemagglutinins though homotoxins are either absent, or present only in such minimal amount as might be accounted for by the leucocytes in the blood inoculum. Conversely, if rat spleen is used to immunise an agglutininsensitive rat, no haemagglutinins are formed, but homotoxins are demonstrable in considerable amount (Table XVII). The chief points of difference between iso-agglutinins and chromatolysins are set out in Table XIX. A hypothesis which fits all the known facts is that the agglutinins appear in response to surface cytoplasmic antigens, the homotoxic chromatolysins to nuclear antigens. It is, on this assumption, not surprising that the titre of these two antibodies should run more or less parallel, since, under ordinary conditions, when nucleated cells are injected the amount of surface and of nuclear antigen would be comparable. The facts that red blood corpuscles give rise only to agglutinins and that rat serum alone evokes neither agglutinins nor chromatolysins, support this hypothesis. It is fortunate that iso-agglutinins, even when evoked by nucleated cells, do agglutinate red blood corpuscles, since this supplies a much more ready means of demonstrating their existence and their titre than the laborious and tedious tissue-culture tests by means of which the existence of homotoxins was first discovered (5). (3) On the Basis of Specificity and of Individual Variation in Response to Antigens: In considering the specificity of the reactions between nucleated cells and cytotoxic sera, too much attention may be focussed on the antibody and too little on the antigen, though the latter is the more fundamentally important of the two factors. It is of value to reverse this point of view and, taking the agglutination of cells as an example, consider specificity, primarily as dependent upon antigenic structure and affinity. When a rat is immunised again Jensen rat sarcoma, agglutinins appear in the rat's serum which are capable of clumping the red blood corpuscles of some rats, but not of others. This cytologic selectivity is not due solely to the nature of the agglutinins in the antiserum, for they agglutinate not only red blood corpuscles, but nucleated cells, normal as well as malignant. The factor that mainly determines which cells shall be clumped, and which not, is the presence or absence of the adequate agglutinogen in those cells. The titre of agglutinins varies from one immune rat to another and from day to day; 411 AGGLUTINATION TESTS IN STUDY OF TUMOUR IMMUNITY TABLE XX: Showing that in Rats Immunised against Homologous Cells the Titre of Agglutinins Is Inversely Proportional to the Titre of Agglutinogens in the Red Blood Corpuscles of the Rat Immunised * Rat Immunised to Serum of Immunised Rat plus Agglutininsensitive R.B.Cs. Titre of Agglutinins Cells of Immunised Rat plus Serum of Anti-].RS. Rat R. 19. Titre of Aggiutinogens Cells of Rat in Own Serum Control for Cell Suspension Result of ].R.S. Implant ++± ++± + ± ± ± 0 0 Regressed 0 0 0 0 ± ± + 0 0 0 0 0 Regressed + ± 0 Grew Rat blood R.C.L.1 L.C.C.H.2 I..C.I.. 3 R.C.C.H.4 R.C.B.5 L.C.B.6 0 0 Grew Rat testis R.C.C.l RC.C. 2 RC.I.. 3 I..C.L.4 +++ ++ ± ± 0 * The anti-rat-blood rats 1 and 6 and the anti-testis rats 2 and 3 had ].R.S. implanted into them; it will be seen that when the agglutinogen content of the rats' red blood corpuscles was low the implant regressed; conversely when the agglutinogen content was high the ability to form agglutinins and chromatolysins was low and the implant grew progressively. the agglutinogen content of the cells is an inherited and extraordinarily stable factor, determinable by selective breeding, but unalterable after birth by any agency yet known. We may regard the high agglutinability of the red blood corpuscles in certain rats as evidence that these cells contain an unusually large quantity of agglutinogen, and for this reason one would expect them to be especially active as antigens, but another and an important deduction can be drawn, namely, that a rat whose blood corpuscles or other cells contain much agglutinogen will not itself be capable of producing the corresponding agglutinins. This results from the fact that unless a substance is "alien" to the animal it is inoculated into, it will not act as an antigen. If agglutinogen is injected into a rat whose red blood corpuscles already contain that substance, we are not supplying an " alien" antigen and no agglutinin will be formed. Indeed from the experiments recorded in Section 11 (p. 405) and in Tables XVII, XX, XXI, XXII, and XXIII, we may conclude that, inter alia, the ability of an animal to produce agglutinin (antibody) varies inversely with the agglutinogen (antigen) content of its cells. It will be shown later that this law has an important bearing on natural resistance to tumour implantation. See Tables XXI-XXIII. The results obtained allow one to develop further the hypothesis that 412 THOMAS LUMSDEN XXI: S/wwing That Rats in Which a Tumour is Growing Progressively N_ Contain Agglutinins in Their Serum, While Their Red Blood Cells Contain an Unusually High Titre of Agglutinogens for Unselected Rats of the London Lister Breed TABLE Serum on Cells R.S.C.H. Titre of Agglutinins Cells with Serum of R.C. 19. Titre of Agglutinogens 0 0 0 0 0 0 0 0 0 0 0 ± ± + + + ± 0 0 0 0 0 0 0 0 0 0 0 12 X 5 0 + 0 10 X 5 5 X 2 0 0 + + 0 0 0 0 + + 0 0 0 Size of Tumour in Centimeters Cells with Own Serum Nov. 22, '37 RC. L.C. B.C. RS. L.S. 8.5. RC.L.S. R.D.S. L.D.S. 8.0.5. R.C.L.D.S. Nov. 8, '37 R.C.L.S. 6 7 7 7 5 5 6 6 7 7 6 X X X X X X X X X X X 1.5 1.6 1.5 1.6 2 1.5 1.7 1.6 1.7 1.5 1.2 Nov. IS, '37 R.S. B.C. Removed Tumours RC. 8.C.(S). 8.C.(L). + ± ± ± + ± cellular antigens vary in activity in proportion to the degree in which they are " alien" to the animal into which they are inoculated. Thus heterologous cells are a much stronger antigen than homologous cells and, as far as is known, autologous cells (with the exception of spermatozoa and possibly of cancer cells) do not act as antigens at all. Cancer cells, presumably because they are more" alien" and invasive, are a more active antigen than any other homologous type of cell. Next in order of potency are splenic fragments, probably on account of the large number of wandering macrophages which they contain. Definitely less effective are fixed tissue cells such as those of the kidney or testis, and least active of all are red blood corpuscles. Another consideration germane to tumour immunity is that within reasonable limits, the more active a celt is as an antigen and the more complicated its antigenic pattern, the more sensitively and specifically it should react with the antibody it evokes. For this reason antisera produced by inoculation of cancer cells have a degree of specificity against malignant cells quite apart from specific" anti-cancer bodies" the existence of which has been suggested as the result of previous experiments (7).2 2 It is difficult to demonstrate unexceptionably the existence of truly specific anticancer bodies because they are always accompanied either by homotoxins or by increased" heterotoxins. Two facts, however, indicate that they do exist. (1) It is shown in a former paper (7) that the serum of a J. R. S.-immune rat is much more toxic than normal rat serum to tissue cultures of mouse cancer. This is not so in the case of cultures of mouse spleen. In those experiments heterotoxins are not increased, and since homotoxins which are present are not toxic to heterologous tissues, the facts strongly suggest the existence of specific anticancer bodies in the J. R. S.-immune rat serum. (2) The second fact emerged during the experiments recorded in this paper. It appears to be pos- 413 AGGLUTINATION TESTS IN STUDY OF TUMOUR IMMUNITY TABLE XXII: Showing Tha; the Ability to Form Iso-agglutinins Varies from Rat to Rat and That It Is in Inverse Proportion to the Agglutinogen Content of the IndividuaJ Rat's Red Blood Cells: J.R.S. Non-Takes and Regressions L.C.R.S. R.S. R.C.L.S. R.C.L.D.S. B.S. R.D.S. B.D.S. L.S. L.C.R.S. L.D.S. B.D.S. L.C.- Serum on Cells of R.S.C.H. Agglutininsensitive Rat Titre of Agglutinins Cells with Serum of R.C.19 Anti- J.R.S. Rat Titre of Agglutinogens Control Cells on Own Serum, For Comparison in Estimating Low Titres +++ +++ +++ +++ ++± ++ +± ± ± ± ± 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 ± 0 ± -± 0 0 ± ± 0 0 - In this rat the tumour grew for a long time, but ultimately disappeared.' Possibly it had a small titre of agglutinin at some time which was missed as the serum was not examined regularly. (4) The Relation of These Experiments to the Study of Tumour Immunity: It has already been shown (7) that: (i) The serum of each animal normally contains antibodies (heterotoxins) lethal to nucleated cells of every foreign species which has been treated, but not to homologous cells. (ii) If the living nucleated cells from one animal are injected into another animal, cytotoxins appear in the serum of the latter, lethal to the cells used as an antigen. (a) If the cells inoculated as an antigen are from a heterologous species, not only are the non-species specific heterotoxins increased in titre, but antispecies bodies are produced in large amount. These anti-species bodies are toxic to the cells of the species or group from which the antigen was taken, but to no other variety of foreign cells, i.e. they are species-specific. (b) If the cells inoculated as an antigen are homologous they evoke antibodies specifically toxic to the wandering cells (cancer cells and macrophages) of animals of their own species or group = homocytotoxins or homotoxins, These antibodies are chromatolytic, but do not lyse red blood corpuscles or damage tissue cultures of fixed tissues (e.g. heart or kidney). The inoculated sible to predict in wbich rats a J. R. S. implant will grow and in which it will regress only by using the serum of a rat immunised against malignant cells (J. R. S.) in the estimation of the agglutinogens on which the prophecies are based. The sera of rats immunised against rat spleen or testis fail to give selective results. This suggests that it is because the J. R. S.-immune rat serum contains anticancer bodies that it reacts with and can be used to estimate the particular agglutinogen whose presence or absence determines the fate of tumour implantation in the rat whose red cells are being tested. 414 THOMAS LUMSDEN animal's own wandering cells are " protected" in some unknown way against these homotoxins and are unharmed." ( 5) At least one variety of autocytoxin exists. The serum of a male rat, mouse or guinea-pig is toxic to its own spermatozoa. The protocols in this paper show that cell agglutinins are formed in association with the cytotoxic chromatolysins just mentioned and that the former can be used as an approximate index of the latter. Both from the point of view of confirmation and of extension of previous experiments, this is an advance of practical value, since the simple and rapid agglutination tests make it possible to investigate even unlikely possibilities with negligible loss of time. In every essential direction these agglutination experiments confirm the more laborious and difficult, if more direct and conclusive, tissue culture tests. Thus the demonstration by Lumsden and Phelps that, during regression of an implanted tumour, chromatolysins can invariably be detected in varying quantity in the serum of the rat concerned (see Table XIV) can be confirmed (since the titre of isoagglutinins and homotoxins run parallel) easily and cogently by demonstrating that: (a) If a progressively growing tumour results from an implantation of cancer, isoagglutinins are never demonstrable in the serum of the rat concerned (Tables X-XIII). (b) When spontaneous regression occurs, isoagglutinins can invariably be demonstrated if frequent tests are carried out (Tables X-XIII). (c) Occasionally while in a rat a tumour is still enlarging, isoagglutinins begin to appear in its serum. If this happens the tumour always ceases to grow and ultimately disappears (Table X, no. 3; XI, no. 4). These facts suggest that chromatolysins and their associated agglutinins are closely related to the mechanism by which an animal resists the invasion of its tissues by cancer cells implanted into it and that they are, in part at least, the basis of natural resistance. It appears that an animal's natural resistance is directly proportional to its capability to produce agglutinins and the more important chromatolysins, and so is inversely proportional to the amount of agglutinogens in its body cells, of which those in its red blood corpuscles act as an indicator. If this be so, from estimating these agglutinogens by means of the serum of a rat immune to Jensen sarcoma we should be able to predict with reasonable accuracy which rats, out of any series into which tumour cells are about to be implanted, will develop a progressively growing tumour and in which spontaneous regression will take place. Table XXIII shows with how much accuracy this prognostication can be achieved, but the test is a delicate one and in each experiment the criterion varies with activity of the agglutinating serum used and with the virulence of S Basis of Protection: Since the above was written, it has dawned upon me that the interdependence and yet segregation of antigen and antibody supply a ready, now almost a self-evident, explanation of the protection of an animal's own cells from antibodies made by it-autologous cells contain none of the adequate antigen. That is why the animal was capable of forming the antibody. If, for example, the cells of a J. R. S.-implanted animal contain no agglutinogen (antigen), it will be competent to form agglutinins and will destroy the implant. Its serum will agglutinate the cells of other non-resistant rats (since they contain agglutinogen) but will have no effect upon its own cells because they contain no antigen. 415 AGGLUTINATION TESTS IN STUDY OF TUMOUR IMMUNITY TABLE XXIII: Showing the Degree of Accuracy with Which It is Possible to Predict the Outcome of J.R.S. Transplantationfrom Estimate of Agglutinogens in R.B.Cs.* Rats RB.Cs. Rats R.B.Cs. + Serum Rat of Prophecy R.C.19 Titre of Agglutinogens Result Serum of Rat + R.B.Cs. of RS.C.H. Agglutinins + Serum Rat of Prophecy R.C. 19 Titre of Agglutinogens 3 ± + ± 4 0 S 11 ± ± ± ± ± ± ± Grow Right 0 35 12 0 Regress Right 36 13 0 Regress Right 37 14 0 Regress Right ++± +++ ± 38 15 Grow Right 0 39 Grow Right 0 17 ± ± ± Grow? Right 18 0 Regress Right 19 0 Regress Right 20 ± ± ± ± ± Grow? Right Grow? Wrong Grow? Right 0 46 Grow? Wrong ± 47 Regress? Wrong 0 48 1 2 6 7 8 9 10 16 21 22 23 24 Grow 25 Right 0 Grow Wrong + 26 Grow? Right 0 27 Regress Right +++ 28 Grow? Right 0 29 Grow? Right 0 30 Grow Right 0 31 ± ± ± ± ± ± ± ± ± ± Grow Serum of Rat R.B.Cs. of R.S.C.H. Agglutinins + Result Right 0 Grow Right 0 Grow Right 0 Regress Wrong 0 Grow Right 0 Grow Wrong Regress Right Grow Wrong Grow Wrong Regress Right 0 Regress Right ± ++± + ± ± +± ± Grow Right 0 ~ Grow Wrong + Grow Right 0 Regress Wrong 0 40 ± ± ± Regress Wrong 0 0 41 0 Regress Right +± ± 42 0 Regress Right 43 0 Regress Right ++ +± ++ 0 44 Right 0 45 +± :!: ± ± ± Grow ± Regress Right +± Grow Right 0 Grow Right 0 Grow Right 0 Grow Right 0 32 Grow? Wrong ± 33 Grow? Right 0 34 * The rats in this table were tested in 4 consecutive batches of 12 rats each (November and December 1937). Rats 1 to 36 were black hooded white London rats, rats 37 to 48 were, in order, 2 cream hooded, 1 agouti hooded, 4 fawn, and 5 black rats. The criterion varies in each experiment with, among other factors, the age and breed of the rats, the titre of cell agglutinins in the serum of the ].R.S.-immune rat used, and with the virulence of the tumour cells implanted. Hence even when the conditions are made as nearly comparable as possible, complete success in prognosis cannot be expected. One striking fact emerges from this and similar experiments. It is that when the titre of agglutinogens is nil (subminimal) the tumour implant invariably regresses and prophecy in this instance is 100 per cent correct. the tumour cells implanted, among other factors. With sufficient experience and sensitivity, however, the prognosis seems to be accurate enough to indicate that the principles upon which it is based cannot be far from the truth. A 416 THOMAS LUMSDEN striking fact is that whenever the titre of agglutinogens is nil, regression invariably takes place. It would be difficult to find a more perfect example of simple and balanced mechanism than that responsible for natural resistance to invasion of the body by alien cells. When on account of the low antigen content and consequent insensitivity of an animal's cells a high titre of antibody is required, this animal has a proportionally high ability to produce it. How delicate this compensatory mechanism is can be appreciated from a careful study of Tables XX-XXIII. It seems. unlikely that this highly organised and regulated mechanism should be merely fortuitous and purposeless; yet we cannot conceive that it has been evoked (by gradual survival of the fittest) in response to circumstances (implantation of tissues and so on) which could hardly arise naturally, and which have occurred artificially only for so short a space as forty or fifty years. It is more reasonable to suppose that this mechanism of natural resistance is related to the prevention of the invasion of one tissue by another within the limits of an individual body, and that investigation of this mechanism may throw light on the basis of the differentiation of tissues, and on Nature's method (quite possibly often successful) of preventing spontaneous cancer. The experiments recorded above refer to implanted tumours alone, and the conclusions drawn from them are by no means necessarily applicable to the spontaneous tumours or the lower animals or of man. Yet in the study of tumour immunity, as we pass from the heterologous to the homologous, and finally to autologous, we find that Nature's method of opposing invasion is comparable for the first two; heterotoxins and antispecies bodies invariably deal successfully with heterologous implantations; agglutinins and homotoxins often succeed in repelling the invasion of homologous cells. It may be that a similar though more refined and elusive mechanism exists which controls the invasion even of autologous cells, for example the penetration of the chorionic villi into the uterine wall. In other words, invading cells may be opposed by similar means whether they are attempting to invade a heterologous, a homologous, or an autologous tissue. SUMMARY AND CONCLUSIONS ( 1) The agglutinability of the red blood corpuscles of normal rats varies widely. High agglutinin sensitivity is peculiar to certain individual rats. It is hereditary and constant, but in the absence of selective breeding it is not an invariable characteristic of any particular strain of rat. (2) There are no blood groups in rats and they do not produce isohaemolysins demonstrable in vitro. (3) The sera of normal untreated rats never contain iso-agglutinins, nor do the sera of rats immunised against heterologous tissues such as mouse or guinea-pig spleen. (4) All rats immunised against homologous normal or malignant nucleated cells develop iso-agglutinins and homotoxic chromatolysins in their sera, but they vary much individually in their capacity to produce these antibodies. AGGLUTINATION TESTS IN STUDY OF TUMOUR IMMUNITY 417 (5) Iso-agglutinins can best be demonstrated by applying them to readily agglutinable rat red cells, i.e. red cells containing a high titre of agglutinogens. The cells of ordinary unselected rats are unsuitable for this purpose. (6) The activity of any cell as an antigen, and the degree of its reaction with its specific antibody, vary directly with its antigen content. Conversely, the ability of any particular animal (e.g. rat) to produce antibodies (e.g. isoagglutinins) is in inverse proportion to the antigen (e.g. agglutinogen) content of its own cells. (7) When evoked either by the regression of an implanted tumour, or by inoculation of homologous nucleated cells, the titres of iso-agglutlnins and of iso-chromatolysins run closely parallel. (8) The more" alien" and" invasive" the cells used as antigens are, the higher the titre of antibodies they evoke. Thus heterologous are more powerful antigens than homologous cells, and autologous cells (except spermatozoa and possibly cancer cells) are non-antigenic. Of homologous nucleated cells, cancer cells have been found to be the most powerful antigens; next come tissues with many wandering macrophages, e.g, spleen. Fixed tissue cells, e.g, testis or kidney, are less effective in the production of both agglutinins and of chromatolysins. Red blood cells generally evoke Iso-agglutinins, but do not give rise to iso-chromatolysins, while blood serum, free from cells, evokes neither of the cytotoxins named. (9) The sera of rats in which a Jensen sarcoma is growing progressively never agglutinate even readilyagglutinable rat red blood cells. The sera of rats in which a tumour is regressing, or in which an implantation has failed to grow, always contain iso-agglutinins and chromatolysins at some period. ( 10) The natural resistance of any rat to tumour implantation (J. R. S.) is directly proportional to its capacity to produce agglutinins and chromatolysins and is inversely proportional to the amount of corresponding agglutinogen in its body cells, of which those in its blood corpuscles act as an approximate index. It follows that, by estimating these agglutinogens by means of the strongly agglutinating serum of a rat immune to Jensen sarcoma, it is possible to select certain rats in which a tumour graft is sure to regress, and with somewhat less accuracy others in which it will grow progressively. NOTE: The writer is grateful to the British Empire Cancer Campaign for its constant and generous support, financial and otherwise. He thanks also his colleagues, both clinical and scientific, at the London Hospital for help in every way possible. REFERENCES 1. BORDET, J.: Ann. de l'Inst. Pasteur 12: 688, 1898. 2. EHRLICH, P., AND MORGENROTH, ].: Bed. klin. Wchnschr. 37: 453, 1900. 3. TODD, C., AND WHITE, R. G.: Proc. Roy. Soc., ser. B, 82: 416, 1910; 84: 255, 1911. ]. Hyg. 10: 185, 1910. 4. TODD, C.: Proc, Roy. Soc., ser. B, 106: 20, 1930. 5. LUMSDEN, T., MACRAE, T. F., AND SKIPPER, E.: J. Path. & Bact. 39: 595, 1934; 40: 418, 1935. 6. LUMSDEN, T., AND PHELPS, H. J.: Am. J. Cancer 29: 517, 1937. 7. LUMSDEN, T.: Am. J. Cancer 31: 430, 1937. 8. LUMSDEN, T.: Am. ]. Cancer 15: 563, 1931. 9. GORER, P. A.: J. Path. & Bact. 44: 691, 1937.