Characterization and significance of donor-reactive B cell antibodies in current sera of kidney transplant patients.

The specificity and class of antibodies resulting in a positive B cell crossmatch were studied in 47 kidney-transplanted patients. The study was performed to determine instances where a positive B cell crossmatch would not be deleterious to the survival of the graft. In order to determine the specificity and class of the antibodies, we used monoclonal antibodies to HLA-A,B,C and DR antigens to block cytotoxicity of sera, and the reagent DTT to characterize the immunoglobulin class. We found that graft survival in patients with DR antibodies was significantly better than in patients with class I antibodies (P less than 0.02). No difference in graft survival in patients with IgM antibodies versus patients with IgG antibodies was observed. The presence of weak HLA class I antibodies in patient's sera only detected as reactivity on B lymphoid cells should be considered a contraindication to transplantation. Thus our study shows that a fraction of patients who have cytotoxic B cell reactive antibodies at the time of transplantation can be successfully transplanted, provided the specificity of each serum is defined prior to transplantation.