Different patterns of donor MHC antigen induction in rat kidney allografts following active and passive enhancement.

We compare the expression of donor class I and class II major histocompatibility complex antigens in DA kidney grafts transplanted to PVG recipients treated by different protocols of donor-specific immunosuppression. MHC expression was evaluated using donor-specific antibodies and assays by immunohistology and quantitative absorption analysis. PVG recipients were either untreated or treated by (A) twice-weekly intravenous injections of 0.5 ml DA blood for 12 weeks; (B) 0.5 ml DA blood intravenously at 7 days pregraft; (C) as for (B), but with the addition or oral cyclosporine at 10 mg/kg/day from the day of grafting; and (D) passive enhancement with DA anti-PVG serum. Grafts were assessed at 3, 5, and 7 days after transplantation. In untreated controls at day 3, there is a periarteriolar leukocyte infiltrate, weak or absent class II induction, but strong class I induction. Class II induction in untreated controls is maximal at day 5. We confirm that active enhancement by blood transfusion, even using the intensive protocol of twice-weekly transfusions for 3 months, results in accelerated leukocyte infiltration and accelerated donor class I and class II MHC induction. At day 3, there is an intense, diffuse leukocyte infiltration and maximal class II induction. Cyclosporine treatment of blood-transfused recipients reduced the leukocyte infiltration and MHC induction to levels seen in untreated controls--i.e., the accelerated MHC induction caused by the transfusion was partially reversible by cyclosporine. In passively enhanced recipients, leukocyte infiltration and class I MHC induction were similar to untreated controls. However, class II induction was much delayed, not being evident until day 7.