Differential immunogenicity of HLA mismatches: HLA-A2 versus HLA-A28.

The immunogenicity of human leukocyte antigen (HILA)-A2 versus HLA-A28 was analyzed by antibody production, cytotoxic T-lymphocyte (CTL) induction, and graft survival. We observed that an HLA-A2 mismatched child in HLA-A28(+) women leads to HLA-A2 specific antibodies in 32% of the women (n=31), whereas in the case of an HLA-A28(+) child and HLA-A2(+) women (n=30), no HLA-A28 specific antibodies were found (P<0.002). Also, the CTL precursor frequencies were significantly lower against HLA-A28 compared with CTLp frequencies against HLA-A2 (P=0.012). Finally, the kidney graft survival was slightly better in HLA-A2 positive recipients transplanted with HLA-A28 mismatches. We can conclude that single HLA-A28 mismatches are less immunogenic in HLA-A2 individuals compared with single HLA-A2 mismatches in HLA-A28 individuals, which is probably because the mismatched epitopes on the HLA-A2 molecule are unique epitopes, whereas the mismatched epitopes on HLA-A28 are shared by other HLA-A and HLA-B molecules.