Expression of HLA-B12 on platelets, on lymphocytes and in serum: a quantitative study.

Expression of the antigen HLA-B12 on platelets, on lymphocytes and in serum of normal subjects was studied using several quantitative techniques. HLA-B12 was found to be expressed on platelets from each of 25 heterozygous HLA-B12-positive donors in amounts varying about 35-fold from weakest to strongest. Expression of B12 on platelets was enhanced in the presence of the first locus antigen A11, but decreased in the presence of A2, A3, and Aw28. The antigen was expressed in equal strength on lymphocytes sampled from the same donor population. Serum content of B12 assayed in five subjects was found to be roughly proportional to the expression of that antigen on platelets. Expression of B12 on platelets is under genetic control but the precise mechanism of inheritance has not yet been defined. The applicability of these findings to transfusion of single donor platelets to alloimmunized patients is under investigation.