Suppressor cell activity of cells infiltrating rat renal allografts prolonged by perioperative administration of extracted histocompatibility antigen and cyclosporine.

Suppressor T cells were identified in situ within renal allografts of hosts rendered unresponsive by perioperative administration of donor histocompatibility antigen, which was extracted from donor spleen cells with 3M KCl, combined with cyclosporine (Ag-CsA). Infiltrating cells harvested from Buffalo (BUF, RT1b) renal allografts ten days after transplantation into Wistar-Furth (WFu, RT1u) rats treated with a single i.v. injection of 5 mg 3M KCl-extracted donor antigen (Ag) combined with a three day course of CsA inhibited the mixed lymphocyte culture (MLC) reaction between normal responder WFu and irradiated BUF cells (79.3% suppression, P less than 0.001), but not third-party Brown-Norway (BN, RT1n) stimulator cells (-5.4% suppression, NS). The suppressor effect was not due to cytolysis: the infiltrating cells did not lyse 51Cr-labeled concanavalin A (Con-A) blastoid BUF cells, as did the infiltrating cells from nonimmunosuppressed recipient allografts undergoing rejection responses toward BUF (49% specific cytolysis, E/T = 25), but not third-party BN, target cells five days after transplantation. The suppressor cells were nonadherent to plastic dishes and sensitive to monoclonal antibodies (Mab) W3/13 HLK (pan-T cells: % suppressor -17.9) or cytotoxic/suppressor cells with Mab OX-8 (-5.0% suppression), but not W3/25 (helper; 48.6% suppression, P less than 0.025). Moreover, adoptive transfer of 10(6) infiltrating cells from Ag-CsA-treated recipient allografts into virgin WFu hosts prolonged primary BUF graft survival from 7.2 to 14.0 days (P less than 0.05), but not third-party BN grafts (treated MST = 11.9 +/- 3.9 days versus untreated MST = 11.0 +/- 2.9 days, NS). On the other hand, infiltrating cells from CsA-only-treated recipient allografts could not transfer this effect (MST = 7.7 +/- 0.5 days, P less than 0.01). Finally, retransplantation of the BUF allograft from the Ag-CsA treated rat to a syngeneic, virgin WFu host ten days after primary transplantation yielded prolonged survival with MST 11.4 +/- 2.3 versus control primary graft survival in untreated animals of 7.2 +/- 0.6 days (P less than 0.001). BUF allografts from treated WFu hosts retransplanted into third-party BN rats did not display prolonged graft survival (MST = 9.2 +/- 1.1 days) compared with primary BUF grafts in untreated BN recipients (MST = 9.2 +/- 2.0 days, NS). The presence of suppressor T cells both in the spleen and in situ in renal allografts following Ag-CsA treatment suggests that local mechanisms may augment systemic elements to control the generation of alloimmunity.