Download The Case of the Probable anti-Lw

The Case of the Probable anti-Lw
INTRODUCTION AND HISTORY
1940 - Landsteiner and Wiener injected Rhesus-monkey red blood cells
into rabbits. They called this antibody anti-Rh
1941- Levine & Stetson's human antibody was shown to have the same
pattern of reactivity as the rabbit anti-Rh antibody.
1942 - Fisk and Foord demonstrate a difference between rabbit and
human anti-Rh.
1963 - Levin et al prove that human and rabbit anti-Rh do not react with
the same antigen.
1982 - Lw is divided into a three antigen system
Development of the Lw antigen
system
- The Lw antigen is independent of the Rh genes, but, in order to express
itself, the Lw glycoprotein (ICAM 4) still requires interaction with the
Rh protein. For example, Rh+ red cells express LW more strongly
than Rh negative cells.
- Initially a numerical system was used to identify Lw. E.g. LW1, 2 etc.
-  After the Nea gene was shown to be allelic to Lw, it was then
renamed Lwa and Lwb.
-  Lw (a+b+) is defined by an alloantibody produced by an individual
with an inherited Lw (a-b-) phenotype.
- The null phenotype Lw (a-b-) is the result of a partial gene deletion
and is extremely rare.
Phenotypes and frequencies in Europeans: Reactions
with Anti –
Lwa
Lwb
Phenotype
%
+
0
Lw (a+b-)
97
0
+
Lw (a-b+)
3
+
+
Lw (a+b+)
Very rare
0
0
Lw (a-b-)
Very rare
FREQUENCY:
In most populations, Lwa has a higher frequency, occurring in essentially
100% of donors, compared to Lwb which occurs in only 1–8% of
Europeans.
Characteristics of Lw:
- Lw is expressed strongly on the red cells of neonates in equal amounts
regardless of D type
- Frequently appears as autoantibodies
- IgM and IgG
- Reactive at room temperature or on the IAT
- do not bind complement
- react to anti-human globulin
- Resistant to papain, trypsin, sialidase and acid, but are sensitive to
pronase and DTT.
- are stimulated by blood transfusions
CASE STUDY:
- A 69 year old female patient with a history of cold agglutinin disease
presented to Wollongong Hospital and was diagnosed with Waldenstom's
Macroglobulinaemia.
- Initial Group and Screen was O Positive with an anti – E, cold
agglutinins and a C3d positive DAT on a pre-warmed sample. She then
develops an anti-Jka, then an autoantibody and an IgG positive DAT.
- A sample showing a preference for D+ cells was then sent to Red Cross
to investigate a possible anti-D.
- Their report indicated a possible anti – Lw specificity as the sample
reacted against both D- and D+ cord cells. A negative reaction was also
observed with an Rhnull cell.
Specimen not signed - a new signed form and
specimsen will be needed if blood products are
required.
CLINICAL SIGNIFICANCE
Although no Lw antibody has been responsible for any serious HTR or
HDFN it is still important to be careful about its possible identification.
This is particularly important in women during their fertile period due to
the need for anti-RhD prophylaxis.
However, as is evident in this case study, they predominantly do not
present clinical problems from a transfusion therapy perspective.