Electroblotting and immunohistochemical staining for identification of platelet antibodies.

Abstract

The Western blot procedure has been adapted for use with a biotinylated antiglobulin reagent and a horseradish peroxidase complex (Vectastain ABC) to determine specific sites of antigen binding and permit discrimination between various types of platelet antibodies. Monospecific anti-PlA1 antisera or sera containing mixtures of multispecific HLA and unidentified platelet specific antibodies were tested with PlA1 phenotyped platelets. Using monospecific anti-PlA1, one intense band with relative molecular weight (Mr) of 88,000 and corresponding to glycoprotein IIIa was seen with the PlA1+ platelets. With mixtures of antibodies, reactions were seen with platelet specific antibodies without interference from the HLA antibodies; with one serum a band of Mr approximately 135,000 was identified with Baka+, but not Baka- platelets, indicating the presence of an anti-Baka in the serum. The location of the Baka antigen corresponded to the area for GP IIb. With another serum, a band of Mr 88,000 was revealed with PlA1- and some PlA1+ platelets suggesting the presence of an anti-PlA2. Two additional bands of Mr 160,000 and 200,000 were present on all preparations including autologous controls, probably due to the presence of non-specific IgG. Thus, immunohistochemical staining is readily adaptable to the Western blot technique, and antibodies to platelet-specific antigens can be easily differentiated from HLA antibodies.