SUSCEPTIBILITY TO ALLOIMMUNIZATION TO PLATELET HPA-1A ANTIGEN INVOLVES TAP1 POLYMORPHISM

The alloimmunization against platelet HPA-la antigen in mothers of thr ombocytopenic neonates is strongly associated with HLA class II struct ures (DR3 and DR13) and especially with HLA-DR52a antigen (98% of the cases reported here). Because new genes have recently been mapped with in the MHC class II region, we typed TAP1 and TAP2 gene polymorphisms by ARMS-PCR in order to characterize more effectively MHC genes involv ed in this alloimmunization. Our re suits showed that TAP10102 allele was significantly associated with NAIT only in the population of HLA- DR13-DR52a-immunized women (50%) versus HLA-DR13-DR52a controls (20%) (p < 0.05), and not in HLA-DRS-DRS 2a-immunized women versus HLA-DR3-D R52a controls. There is no linkage disequilibrium between TAP10102 an d DRB113 alleles (Delta = -0.0063) that could account for this result . The higher frequency of TAP10102 allele among HLA-DR13-DR52a-immuni zed women suggests that HPA-1a antigen presentation and recognition ma y be influenced by nonclassic HLA class II gene polymorphisms, or that other linked but yet unknown genes could interfere.