Immunoregulatory (antiidiotypic ?) serum factors in pre‐ and posttransplant sera of renal transplant recipients

Sera of 40 renal transplant recipients were tested for the presence of antiidiotypic antibodies against autologous donor‐reactive recipient T cells. From each patient, a series of cell cultures was established. The cultures were restimulated with specific donor cells for 2 weeks. Cells of each culture were tested in 2‐day MLC assays with the addition of autologous pre‐ or posttransplant serum or 2 control sera. For each patient the proportion of cultures was calculated that was suppressed or stimulated by autologous sera. Stimulation by pretransplant serum was correlated with the number of pretransplant blood transfusions (p<0.01), but not with graft survival. Within 2 months posttransplant, suppressive and stimulating serum factors were induced that correlated significantly with transplant outcome (p < 0.01). Patients with good graft outcome had significantly more cultures that were suppressed by posttransplant serum than patients with rejections. Conversely, stimulation was associated with graft rejection. Our data suggest a posttransplant induction of suppressive and stimulative serum factors that regulate the reactivity of donor‐reactive cell clones.