The analysis of sera containing different platelet-reactive antibodies, eg, autoantibodies, platelet-specific alloantibodies like anti-PIA1, - PIA2, -Baka, and HLA antibodies, is still difficult. Recently, monoclonal antibodies against major platelet membrane constituents (glycoproteins IIb/IIIa and Ib and HLA class I molecule) have become available. In this report we describe a new assay that takes advantage of these highly specific reagents to investigate selectively platelet reactive antibodies against epitopes on different glycoproteins. The reliability and specificity of this assay is demonstrated with known platelet-reactive autoantibodies and alloantibodies (anti-PIA1, -Baka, - Pen). The discovery of a PIA2 antibody in a serum of a polytransfused patient underscores the efficiency of this technique. Possible applications of this assay are discussed in detail.

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A case of neonatal alloimmune thrombocytopenia due to fetomaternal incompatibility against the platelet-specific antigen Zwb (PlA2) is described. The antibody was of the IgG class and did not fix complement in vitro. Its specificity was established by panel identification and by comparison to a Zwb antiserum. Gene dosage determinations of Zwa antigens on platelets of parents and child revealed that the mother was homozygous Zwa Zwa, while father and child were heterozygous for this antigen.

The analysis of sera containing different platelet-reactive antibodies, eg, autoantibodies, platelet-specific alloantibodies like anti-PIA1, - PIA2, -Baka, and HLA antibodies, is still difficult. Recently, monoclonal antibodies against major platelet membrane constituents (glycoproteins IIb/IIIa and Ib and HLA class I molecule) have become available. In this report we describe a new assay that takes advantage of these highly specific reagents to investigate selectively platelet reactive antibodies against epitopes on different glycoproteins. The reliability and specificity of this assay is demonstrated with known platelet-reactive autoantibodies and alloantibodies (anti-PIA1, -Baka, - Pen). The discovery of a PIA2 antibody in a serum of a polytransfused patient underscores the efficiency of this technique. Possible applications of this assay are discussed in detail.