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KJ Kao, DJ Cook and JC Scornik
Class I molecules of human major histocompatibility complex (HLA) are the
most important antigenic system in determining the survival of transfused
platelets in alloimmunized patients. Platelets with reduced expression of a
specific type of HLA antigen may escape specific anti- HLA
antibody-mediated destruction. By using 125I-labeled Fab fragments of W6/32
anti-HLA monoclonal antibody and competitive protein binding assays, we
measured the range of total HLA concentrations on platelets. In 12
individuals examined, the mean number of HLA-A, B, and C molecules per
platelet was 81,587 +/- 20,016 (mean +/- SD); its range was between 54,782
to 116,185 molecules per platelet. After treatment with chloroquine, 79.9
+/- 7.0% (mean +/- SD, n = 6) of HLA antigens were removed from platelets
as determined by binding of 125I-W6/32 Fab. A similar result was obtained
when HLA antigens on chloroquine-treated platelets were evaluated with
immunofluorescence flow cytometry. In contrast, chloroquine treatment did
not remove integral membrane protein such as P1A1 antigens on platelets.
The presence of HLA antigens in the chloroquine eluate of platelets could
be demonstrated to contain HLA antigens similar in mol wts to intact class
I molecules by an immunoblotting technique. These data suggest that 70% to
80% of platelet HLA antigens are adsorbed and that such HLA antigens are
not proteolytic products of integral membrane class I molecules. The origin
of the adsorbed platelet HLA-antigens remains to be determined.
This article has been cited by other articles:
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| Copyright © 1986 by American Society of Hematology Online ISSN: 1528-0020 | |||||||||
