Download (PBMC) of syphilitic patients to produce IL-2

/vWlDJNf~OGY AND
EL.SEVIER
FEZMSImmunology and Medical Microbiology 12 (1995) 17-28
MICROBIOLOGY
The ability of peripheral blood mononuclear cells ( PBMC) of
syphilitic patients to produce IL-2
J. Podwiiiska a**, R. iaba b, M. Chomik a, J. Bowszyc b
a Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, Czerska 12, 53-l 14 Wroctaw. Poland
b Department of Dermatology, School of Medicine, Poznari. Poland
Received 13 February 1995; revised 15 May 1995: accepted 15 May 1995
Abstract
The cell-mediated immune response of importance in protection against Treponema pallidum, is distinctly suppressed in
some stages of the disease. This may be a result of decreased ability of cells to produce IL-2, or IL-2 absorption by different
factors. The experiments were designed to evaluate the ability of peripheral blood mononuclear cells (PBMC) of patients
with different stages of syphilis to produce IL-2, and to investigate the causes which could possibly limit its activity. The
ability of the PBMC of syphilitic patients to produce IL-2 develops at the beginning of the disease, reaching a maximum in
primary seropositive syphilis. In the next stages of the disease this capability is distinctly lowered. The lowest was in
malignant syphilis and tabes dorsalis, i.e. during severe disease. Absorption of adherent cells from PBMC increased the
ability of lymphocytes to produce IL-2. The highest level of this interleukin was observed at the stages of the disease where
suppression was the deepest. Sera of both control and syphilitic patients contained IL-2 inhibitor. Its level was the highest in
early and late latent syphilis where no symptoms of disease were present. In all syphilitic sera a distinctly elevated level of
soluble IL-2 receptors (sIL-2R) was also found. Its high level was noted in sera of patients in which PBMC had the weakest
ability to produce IL-2. These findings suggest that sIL-2R may be bound to IL-2 and in this way would lead to weakening
of T cell function and of resistance against Treponemu pallidurn infection.
Keywords: Treponema pallidum; Interleukin-2; Serum IL-2 inhibitor; Soluble IL-2 receptor; Lymphocyte marker
1:Introduction
In syphilis, as in other infectious diseases where
bacteria are intracellular,
the cell-mediated
immune
response plays a pivotal role in host defence against
infectious agent [I]. This form of immunological
response, as is known from studies on experimen-
Corresponding author. Tel: +48 (71) 73 22 74; Fax: +48
(71) 67 91 Il.
l
tally induced syphilis in rabbits, is, in some periods
of the disease duration, distinctly inhibited [l-3].
This was found as diminished ability of lymphocytes
to produce migration inhibition factor (MIF), which
affects various antimicrobial functions [4]. and weakening the ability to mount delayed type hypersensitivity (DTH) [5]. R ecent data have also indicated that
spleen cells of syphilitic rabbits are not able to
produce antitreponemal lymphotoxin (ATJL)[6] which
kills treponemes both in vitro [7,8] and in vivo [9]. In
some periods in the course of syphilis in rabbits IL-2
0928-8244/95/.%X9.50 0 1995 Federation of European Microbiological Societies. All rights reserved
SSDI 0928-8244(95)00043-7
18
J, Podwibka
et al. / FEMS Immunology and Medical Microbiology
production is also markedly decreased [ 10,l l]. IL-2
is known to play a key role in development of
various forms of cellular immunity by activation of
T lymphocytes into cell division and differentiation
into effector cells by means of receptor mediated
IL-2 binding [ 121. Deficiencies in the synthesis of
and/or response to IL-2 have been implicated in
impaired cell-mediated immune reactions and immunity in some infectious diseases [13-161 for which
efficient cell-mediated immunity is very important
for host resistance.
The aim of the present study was to investigate if
human lymphocytes are able to produce this interleukin at different stages of syphilis, in both the mild
and acute course of disease. In addition, the association between production and ability to absorb IL-2,
by serum IL-2 inhibitor or serum soluble interleukin
2 receptor (sIL-2R), was examined. As far as we
know, no reports have been published on IL-2 production by PBMC of syphilitic patients and no information is available on serum IL-2 inhibitor and
soluble serum IL-2R in this disease.
2. Materials and methods
2.1. Cell separation and culture medium
The PBMC were separated from heparinized blood
of 55 patients with different stages of syphilis, and
12 (I 995) 17-28
from 32 healthy people used as a control (Table 1).
The cells were obtained by centrifugation of heparinized blood on a Ficol (Pharmacia, Uppsala, Sweden) Uropoline (Polfa, Poland) density gradient.
Uropoline was used instead of Hypaque M as originally recommended [171. They were washed and
suspended in RPM1 1640 (Gibco, Grand Island, NY)
supplemented with 2 mM glutamine, 0.1 mM sodium
pyruvate, 100 IU ml-’ penicillin, 100 pg ml-’
streptomycin, 5 X 10m5 M 2ME, 15 mM Hepes and
10% foetal calf serum (FCS) at final concentration
for interleukin stimulation and 2% for IL-2 determination. All reagents were from Gibco (Grand Island,
NY).
2.2. Cell culture and IL-2 stimulation
The peripheral blood mononuclear cells (PBMC)
(density 1 X lo6 ml-‘) were cultured in flat-bottomed 96-well microtitre plates (Greiner). Cells from
every patient were cultured in 36 wells (12 with
ConA, 12 with PHA and 12 with medium without
mitogen). Each well contained 100 11-1of cell suspension, 100 ~1 ConA at final concentration of 7.8
pg ml-‘, and PHA at concentration 10 +g ml-’ as
determined from titration or 100 ~1 medium. Cells
were incubated for 24 and 48 h at 37°C in a humidified atmosphere containing 5% CO,. Cells cultured
only in culture medium were used as non-stimulated
controls. At the end of incubation, culture supernates
Table 1
Patients examined with different stages of syphilis
Stages of syphilis
Shortening
No. of
patients
Women
Men
Primary seronegative syphilis
Primary seropositive syphilis
Secondary early syphilis
Secondary relapse of syphilis
Early latent syphilis
Late latent syphilis
Malignant syphilis
Asymptomatic neurosyphilis
Paralysis progressive
Cerebrospinahs syphilis
Tabes dorsalis
prim. seroneg. syph.
prim. seropos. syph.
second. early syph.
second. tel. syph.
early lat. syph.
late lat. syph.
malignant syph.
asympt. neurosyph.
paralysis progr.
cembrospin. syph.
tabes dors.
3
2
5
I
7
I
1
15
3
4
3
I
0
I
3
2
3
3
0
9
0
2
0
TOTAL
55
23
32
Control group
32
13
19
1
2
5
4
4
I
6
3
2
I
J. Podwiriska
et al. / FEMS Immunology
were collected and stored frozen at - 70°C until they
were tested.
2.3. IL-2 determination
IL-2 activity in culture supemates was measured
using ’ H-thymidine incorporation by the IL-2 dependent CTLL-2 cell line (kindly provided by M.
Zimecki), as described by Gillis et al. [18]. Briefly,
CTLL-2 cells cultured in RPMI 1640 medium (supplemented as medium for PBMC, see above) with
addition of 20 IU ml-’ of highly purified human
IL-2 (Biotest) were washed twice in RPM1 medium
immediately before use to remove residual exogenous IL-2, and were adjusted to 1 X 10’ cells ml-‘.
A volume of 100 ~1 of this suspension was distributed into each well of flat-bottomed microtitre
plates which contained 100 ~1 of culture fluid, RPM1
or medium with a range of different concentrations
of standard human IL-2 (Biotest). The cultures were
incubated for 24 and 48 h at 37°C in a humidified
environment containing 5% CO,. During the final 6
h of incubation, the cells were pulsed with 1 &i
“H-thymidine in 20 ~1 PBS (Amersham, Arlington
Heights, IL). The labelled cells were harvested using
an automated Scatron harvester onto glass-fibre filter
strips (Scatron). The fibre glass strips were air-dried
for at least 4 h at 37°C. Individual discs were
punched into 2.5 ml-plastic scintillation vials (Zorza,
Poland) and 2 ml of scintillation fluid (consisting of
8 g POP (2,5-diphenyloxazole (Koch-Light Laboratories Ltd., UK) and 50 mg POPOP (1,4-di[2-(C5
phenyloxazolyll-benzene)
(International Enzymes
Ltd., UK) diluted in 1 1 of toluene (Poch, Poland)
was added to each vial. Radioactivity was determined in a liquid scintillation counter ( p> model LS
3801 Beckman. All data are presented as means from
triplicate cultures of the same tested samples.
2.4. Assay of serum IL-2 inhibitor
The activity of the inhibitor in tested sera was
measured by its ability to inhibit IL-2 mediated
proliferation of a cytotoxic T lymphocyte line
(CTLL-2) by the method of Emery et al. 1191 with
slight modifications. A volume of 100 ~1 of this cell
suspension, prepared as reported above, was added
to each well of a microtitre plate (Greiner) containing 60 ~1 of RPM1 medium, 20 ~1 of tested serum
and Medical
Microbiology
12 I 199.5) 17-28
19
(10% final concentration) and 20 ~1 (20 IU> of
highly purified human IL-2. Controls were: 20 ~1 of
IL-2 and 80 ~1 of culture medium or medium without IL-2 (100 ~1). The cells were incubated for 24 h
at 37°C in a humidified environment containing 5%
CO,. During the final 6 h of incubation the cells
were pulsed with 1 PCi ‘H-thymidine. The cells
were harvested and examined as described above.
The results were expressed as the percentage inhibition of IL-2 response in the presence of serum which
was calculated as follows:
cpm with serum
% inhibition = I -
cpm without serum
x 100
2.5. Detection of serum-soluble IL-2 receptor (slL2R)
Levels of sIL-2R in the serum of patients were
determined using an ELISA test kit from T-cell
Sciences (Cambridge, MA). Briefly, the sIL-2R
available in the test samples or in the standards were
bound to the polystyrene microtiter wells previously
incubated with anti IL-2R monoclonal antibodies.
With washing, non-reacting sample components were
removed. A horseradish peroxidase conjugated antiIL-2R mAb directed against a second epitope on the
IL-2R molecule, was bound to the IL-2R captured by
the first antibody to complete the sandwich. After
washing, substrate solution was added to the wells.
The coioured product of the enzyme reaction was
formed in proportion to the amount of sIL-2R present in the sample. The reaction was then stopped
and the absorbance determined at 490 nm. The IL-2
receptor concentration was determined from the standard curve prepared from 5 IL-2 receptor standards.
The IL-2R standard was the cell-free supernatant
obtained from PHA in vitro stimulated T cells, which
was assigned as a value of 1000 IL-2R U/ml. When
the values were above their standard curve, samples
were retested after dilution and results expressed
accordingly. The final values were expressed as units
per ml (U ml-‘).
2.6. Ability of CTLL-2 cells to proliferate
Before using CTLL-2 cell line in experiments, its
ability to proliferate in the presence of standard IL-2
20
J. Podwihsko et al. / FEMS Immunology and Medical Microbiology
was examined. The IL-2 was used at concentrations
from 1 to 256 U ml -I. The prepared standard curve
indicated the sensitivity of cells and could be used to
determine units of IL-2 designated as indicated in the
previous paper [I 11. Only strongly proliferating cells
were used in all experiments.
12 (1995) 17-28
(Becton Dickinson). Analysis was done using the
computer program BDIS CONSORT 30-Ver F. Each
time 15 000 cells were counted. Only Becton Dickinson reagents were used and the manufacturer’s instruction were followed. As a control, Simultest (IgG
FITC/IgG, PE) was used.
2.7. Absorbtion of adherent ceils
The monocytes were removed from a suspension
of PBMC by adhering the cells to the Petri dishes
during 2 h of incubation at 37°C in a humidified
atmosphere containing 5% CO,.
The venereal disease research
(VDRL) slide flocculation test
2.8.
l
2oo.ooo
180.000
laboratory
=
p<o.I
** = P<O.Ol
n-l
*** = P<O.O5
-.
160,000
This test was performed as described in the Manual of Tests for Syphilis [20].
2.9. Treponema pallidurn haemagglutination
140.000
test
120.000
(TPHA)
This test was performed according to Tomizawa
using reagents of Cellognost-Syphilis H,
(Behring, Germany).
;
100,000
et al. [2l],
2. IO.
Captia
80.000
syphilis-M immunoenzymatic test
60.000
This test was performed using Mercia Diagnostics
reagents as described by Gibowski and Machoriko
[221.
2.1 I. Fluorescent
treponemal antibody absorbtion
40.000
20.000
test (FTA-ABS)
This test was performed according to the method
of Hunter et al. [23].
2.12. Lymphocyte markers
The cell surface markers were analyzed using
monoclonal antibodies against CD, (anti-Leu-3
FITC), Simultest: CD, (anti-Leu-4 FIX), CDs (antiLeu-8 PE and CD25 (IL-2R)) (Be&on Dickinson).
To 100 ~1 of cell suspension 10 yl specific antibodies were added. The mixture was incubated 20-30
min at 4°C and the cells were counted by FACSCAN
Fig. 1. IL-2 production by PBMC during the course of infection.
PBMC were isolated from both normal and syphilitic people with
different stages of disease and were stimulated in culture with a
dose 7.8 pg ml-’ of ConA for 24 h. The culture supemates were
assayed for IL-2 content using an IL-2 dependent CTLL-2 cell
line. The results are expressed as the average f S.D. of cpm of
triplicate cultures (m, average; 0, SD.). 0 = values for PBMC
Controls.
.I. Podwihka et al./ FEMS Immunology and Medical Microbiology 12 (1995) 17-28
2.13. Statistics
21
highest level of IL-2 was found in culture supernates
of lymphocytes stimulated with ConA and PHA (not
demonstrated)
in primary seropositive
syphilis. In
subsequent stages of the disease, the level of IL-2
was decreased and the lowest was in lymphocyte
supemates of patients with malignant syphilis and
tabes dorsalis (difference not statistically significant)
and in asymptomatic
neurosyphilis,
paralysis progressive and cerebrospinal syphilis (difference statistically significant).
Nearly the same level of IL-2
was found when the cells were incubated for 48 h
(data not presented). In culture supemates of nonstimulated lymphocytes the level of IL-2 was low
(from 2000-5000
cpm) when standard IL-2 at a
concentration of 20 U ml-’ was used as a control, to
check ability of CTLL-2 cells to proliferate, the level
was from 140000-160000
cpm (not indicated in
Figs.).
All experiments
were carried out in triplicate;
results were expressed as the mean f SD. Comparison between tests was done by Student’s t-test, with
statistical significance considered to be P < 0.05 and
nonparametric
for comparison
of two independent
median Wilcoxon sum rank tests [24].
3. Results
3. I. IL-2 production by PBMC stimulated with ConA
and PHA
PBMC from patients with different stages of
syphilis (Table 1) as diagnosed on the basis of
serological tests: (VDRL [20], TPHAT 1211, Captia
Syphilis-M [22] and PTA-ABS [23]), and clinical
examination were tested for IL-2 production; results
are shown in Fig. 1.
In comparison with cells from normal people, the
3.2. Suppression of IL-2 production by adherent cells
Taking into account
sent in cell suspensions
the fact that monocytes premay produce prostaglandins
_
250,000
/ * = PCO.05
200,000
150,000
E
!?
100,000
50,000
0
ImPHA
24h +M DPHA
24h-M
konA24h+M
HConA24h-M
6PHA48h+M
n PHA48h-M
1
Fig. 2. Ability of PBMC to produce IL-2 before and after absorption of adherent cells (Man) and stimulation with ConA and PHA for 24
and 48 h.
22
J. Padwihku et al./ FEM.7 Immunology and Medical Microbiology 12 (1995) 17-28
I
12ooo
22o.ooQ
loom
ea,ooo
Bwo
B
wo.ooo
0000
4000
Bo.000
2000
0
0
Fig. 3. Ability cells for IL-2 production and titer of antibodies in sera, measured using the FTA-ABS test.
which inhibit IL-2 production [25] we absorbed adherent cells from PBMC, and lymphocytes were
examined for their ability to produce IL-2 (Fig. 2).
As can be seen from Fig. 2, the culture supernates
from PBMC deprived of monocytes had higher levels of IL-2. The highest level seems to be in those
stages of syphilis where the ability of the cells for
IL-2 production was the lowest as in secondary
malignant syphilis and late stages of neurosyphilis.
In early stages, primary seronegative and seropositive syphilis, this ability slightly increased and in the
control it was virtually unchanged.
20
2B
iBo,ooo
20
z
%
lOO.OW
II
10
Pig. 4. IL-2 production by PBMC and level of IL-2 inhibitor in sera. The results am expressed as the average of cpm for IL-2 and
percentage of inhibition for serum IL-2 inhibitor.
J. Podwihska
et al. / FEMS Immunology
and Medical
Microbiology
~60.066
I2 (1995) 17-28
23
666
Q
666
1w.006
Fig. 5. lL-2 production and level of slL2-R in sera. The results are expressed as the average of cpm for IL-2 and IU ml- ’ for sIL-2R
3.3. IL-2 production and level of antibodies
The ability to produce IL-2 did not correlate with
the titer of antibodies in sera of patients (Fig. 3).
Fig. 3 demonstrates only the level of antibodies
measured by FTA-ABS [23]. Similar results were
obtained when the level of antibodies was examined
by VDRL [20], TPHA [21] and Captia Syphilis-M
[22] (data not presented). The highest level of anti-
bodies was in malignant syphilis and tabes dorsalis
where the ability to produce IL-2 was the weakest.
3.4. IL-2 inhibitor activity
Taking into consideration that, in sera from patients with a suppressed cell-mediated immune response an inhibitor of IL-2 is present 1261 and that
this factor may take part in a mechanism of home-
Table 2
Proportion of lymphocytes with markers CD,, CD, aad CDs at different stages of syphilis
Stages of syphilis
Percentage of lymphocytes with markers:
CD,
C”3
Control group
Primary seronegative syphilis
Primary seropositive syphilis
Secondary early syphilis
Secondary relapse of syphilis
Early latent syphilis
Late latent syphilis
Mahgnant syphilis
Asymptomatic neurosyphilis
Paralysis progressive
Cembrospinalis syphilis
Tabes dorsalis
69.88 f
74.40 f
81.95 f
72.26 f
72.44 f
72.63 f
76.87 f
50.60
74.90 f
54.37 f
68.48 f
68.80
8.38
4.04
7.42
13.65
6.09
8.42
4.60
8.74
2.85
13.48
45.72 f
52.50 f
53.80 *
47.04 *
51.00*
54.53 f
50.39 f
28.70
42.45 *
39.63 f
40.68 f
44.40
C”,
10.05
4.08
9.19
12.18
11.76
8.86
14.80
11.88
1.25
12.49
25.05 f
24.87 f
21.65 f
28.30 f
22.63 f
20.21 f
20.79 f
39.10
31.56 f
26.03 f
3 1.58 f
26.40
6. I8
1.53
12.66
6.23
4.47
5.57
7.9 1
11.78
14.06
7.62
24
i. Podwiriska et al./ FEMS Immunology and Medical Microbiology I2 (1995) 17-28
ostasis, the following questions arise: (1) what is the
level of this factor in sera of patients with different
stages of syphilis; and (2) does any correlation exist
between the serum level of this inhibitor and ability
of cells to produce IL-2?
In all sera of normal people and syphilitic patients
an IL-2 inhibitor was present. The highest level of
this factor in comparison to the control was found in
sera of patients with early and late latent syphilis
where no clinical symptoms of disease were present.
In other stages of syphilis the level of IL-2 inhibitor
was maintained with slight fluctuation as in the
control group.
A comparison of PBMC ability to produce IL-2
with the level of IL-2 inhibitor in sera is shown in
Fig. 4. Only at the beginning of the disease (primary
seropositive syphilis) was the ability to produce IL-2
correlated with an increased level of inhibitor, and in
* = PCO.1
** = Pa01
*** = P<O.O5
secondary early syphilis both IL-2 production and
level of inhibitor were decreased. In other stages of
the disease a high level of inhibitor was accompanied with decreased ability to produce IL-2.
3.5. Soluble serum IL-2 receptor
Other factors which may also be bound to IL-2
and inhibit its activity are soluble serum IL-2 receptors &IL-2R).
In all stages of syphilis the level of sIL-2R was
higher than in the control group and primary
seronegative syphilis. The highest level was in malignant syphilis paralysis progressive and tabes dorsalis where PBMC had a very weak ability to produce IL-2 (Fig. 5).
3.6. Lymphocyte receptor for IL-2
It was interesting to examine the percentage of
lymphocytes T and B with receptors for IL-2 in
different stages of syphilis and their different ability
to produce IL-2.
Independently of the stage of syphilis and ability
to produce IL-2, the percentage of cells with IL-2
receptors was distinctly higher than in the control
group (not indicated).
3.7. Markers of T lymphocytes
Fig. 6. Ability of PBMC to proliferate in the presence of 20 IU of
standard IL-2. The rcaults arc expressed as average f SD. of cpm
of triplicate cell cultures (m. average; 0, S.D.).
The suppression of IL-2 production may be also
connected with the diminished proportion of CD,
and CDs lymphocytes in circulation. The percentage
of cells with these markers as well as CD, in
different stages of syphilis is demonstrated in Table
2.
As seen in Table 2 a diminished percentage of
lymphocytes CD, and CD, was only observed in
syphilis with a severe course of the disease and
distinctly diminished ability to produce IL-Z as in
malignant syphilis ( P < 0.1) and paralysis progressive (P < 0.01). On the contrary, a diminished percentage of ceDs with the CDs marker was seen in
early (P < 0.01) and late latent syphilis (P < 0.11,
where no clinical symptoms of the disease were
present and only a weakly diminished ability of
PBMC to produce IL-2 was found.
J. Podwikka
et al. / FEMS Immunology
3.8. Cell proliferation in the presence of exogenous
IL-2
The proliferation
ability of lymphocytes
in the
presence of IL-2 (20 IU) is shown in Fig. 6.
The greatest capacity for proliferation was seen in
cells from patients with primary seropositive syphilis.
In secondary early syphilis this ability distinctly
decreased but in the next stages (secondary relapse
of syphilis, early and late latent syphilis and asymptomatic neurosyphilis) it was partially restored. In all
stages of symptomatic
neurosyphilis
as well as in
malignant syphilis the ability to proliferate in the
presence of exogenous IL-2 was very low (about one
third of that in the control).
4. Discussion
The results of the present study have demonstrated that the ability of PBMC of syphilitic patients
to produce IL-2 develops from the start of the disease. The highest level of this cytokine was seen in
primary seropositive syphilis. At this stage of the
disease, lymphocytes also had the greatest ability to
produce migration inhibition factor. In the light of
these data, production of both factors (IL-2 and MIF)
at the same time of disease, seems to indicate that
IL-2 may stimulate a cell-mediated immune response
and in this way contribute
to protection against
Treponema pallidum infection. In subsequent stages
of syphilis this ability for IL-2 production was distinctly decreased and fell to a lower value than that
in normal human lymphocytes, at which it was maintained throughout all later stages of the disease. The
lowest level was found in supernates of cells from
patients with malignant syphilis and tabes dorsalis,
i.e. in severe stages of the disease. The data seem to
suggest that decreased ability for IL-2 production
may be an effective cause of increasing progression
of the disease.
The present study has also indicated that absorption of adherent cells from PBMC increased their
ability to produce IL-2. These results are in agreement with those of Tomai et al. [lo] who additionally
indicated 1251 that adherent cells stimulated with T.
pallidum antigen produce PGE, which is generally
considered to be an inhibitory factor [27]. It was also
and Medical
Microbiology
12 f 1995) 17-28
25
interesting to notice that, after absorption of adherent
cells, the level of IL-2 in culture supemates was
higher at those stages of syphilis where deepest
suppression was observed. In the control group the
ability of cells to produce IL-2 was almost unchanged. This seems to indicate that suppression of
IL-2 production may be connected with stimulation
of adherent cells in vivo by T. pallidum.
Suppression of IL-2 production has no influence
on the level of antibodies in sera which seems to
suggest that lack of this interleukin did not disrupt
stimulation of the humoral immune response.
The production and biological activity of IL-2 is
under complex control by cellular and humoral factors known as IL-2 inhibitor present in serum and
other biological fluids [26]. It is believed that serum
inhibitor acts in a homeostatic mechanism to restrict
IL-2 action of the activated T lymphocytes.
In the
presence of this inhibitor, decreased IL-2 production
and response to exogenous IL-2 was found in autoimmune disease [19,28,29] and in infectious disease associated with immunological
defects, such as
lepromatous leprosy [30] or acquired immunodeficiency syndrome (AIDS) [3 1,321. In the present study
all sera of normal people and syphilitic patients
contained IL-2 inhibitor, but the highest level of this
factor was in sera of patients with early and late
latent syphilis where no symptoms of the disease
were present. On the other hand, in secondary early
syphilis, malignant and cerebrospinalis
syphilis with
pathologic symptoms of the disease, the level of IL-2
inhibitor was very low. The data seem to suggest that
IL-2 inhibitor may moderate the manifestations
of
Treponema pallidum infection.
There are some suggestions
that depression of
IL-2 inhibitor is associated with a severe course of
the disease and a poor prognosis, whereas a high
level of inhibitor is associated with good prognosis
in systemic lupus erythromatosis (SLE) [29] and in
rheumatoid arthritis [19]. The mechanism of IL-2
inhibition is as yet unclear. Honda et al. [33] suggested that IL-2 inhibitor could be bound to IL-2 or
to IL-2 receptor competing with IL-2 attachment.
Cells examined in our experiments for the presence
of receptors for IL-2 indicated that independently
of
the stage of syphilis and level of inhibitor in circulation, the percentage of cells with receptors for IL-2
was distinctly higher than that in the control. On the
26
.J. Podwiriska et al. / FEMS Immunology and Medical Microbiology I2 (1995) 17-28
other hand, the ability to proliferation in the presence
of exogenous
IL-2 was the same as the ability of
cells to produce this interleukin.
These results are
difficult to explain. Also, the above data indicate that
in sera of all patients the level of soluble IL-2
receptors (sIL-2R) was high. The highest level was
in sera of patients whose PBMC had weak ability to
produce IL-2 as in malignant syphilis and paralysis
progressive. An elevated level of sIL-2R has been
found also in sera of patients with autoimmune
disease as well as in culture supemates of PBMC of
the same patients [34]. Though we have not examined sIL-2R in culture supemates, nevertheless they
may be present there and may bind IL-2 and in this
way inhibit IL-2 activity. This question will be examined in the future.
Phenotypic
analysis of PBMC indicated that a
severe course of syphilis and weakening ability to
produce IL-2 is accompanied by a diminished percentage of CD, and CD, lymphocytes and increased
percentage of CD,. On the other hand, in syphilis
without clinical symptoms of the disease as in early
and late latent syphilis, the percentage of CD,, cells
was higher than CD,. The diminished percentage of
CD, cells and decreased ability for IL-2 production
or inhibition of its activity may lead to a decrease of
the cell-mediated
immune response and resistance
against Treponema pallidum infection.
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