Influence of antiidiotypic antibody activity on renal transplant outcome.

The presence of cytotoxic HLA antibodies (Ab1) against donor lymphocytes in pretransplant sera is almost always associated with rapid rejection of the renal transplant. We have investigated the possibility that antiidiotypic antibodies (Ab2) to cytotoxic HLA antibodies might modulate the immune response and favorably influence renal allograft outcome. The role of antibodies (Ab3) which potentiate the cytotoxic effect of Ab1 was also studied. Pretransplant sera from 63 patients were tested for inhibitory or potentiating activity in the short antiidiotypic assay. Inhibitory activity was detected in 30 patients and in 28 the transplant survived more than a year. Of patients without antibody activity 11 of 17 had grafts surviving more than one year, and of those showing potentiating activity 11 of 16 were functioning at a year. The difference in transplant survival between the first group and the other two groups was statistically significant (P less than 0.05). There was no significant difference in survival rates between the latter two groups. Potentiating activity is therefore not an independent predictor of transplant failure, whereas the presence of antiidiotypic antibody activity did correlate with improved allograft survival.