THE IMMUNOSUPPRESSIVE ACTION OF SUPPRESSOR CELLS FROM ANTIGEN-CYCLOSPORINE-TREATED HOSTS ON RENAL ALLOGRAFT SURVIVAL

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Abstract
Systemic adoptive transfer was employed to assess the immunosuppressive efficacy of antigen-specific suppressor T (Ts) cells purified from recipients treated with 3MKCI-extracted donor histocompatibility antigen (Ag) and cyclosporine (CsA). Suppressor cells were obtained from Wistar-Furth (WFu, RT-1u) hosts treated with a single i.v. injection of 5 mg 3M KCI-extracted donor Buffalo (Buf, RT-1b) antigen combined with a three-day course of CsA, a group that displays prolonged renal allograft survival (MST 23.2±10.2 days) compared with animals treated with CsA alone (MST 12.2±2.4 days). These noncytolytic, OX-8 phenotype, 800-rad-resistant/1500-rad-sensitive, nylon-wool-nonadherent and cyclophosphamide-sensitive suppressor T cells (1x106) were adoptively transferred ten days after transplantation into virgin, secondary syngeneic hosts-thereby prolonging Buf graft survival from 7.2 to 17.5 days. The suppressor effect was immunologically specific; adoptive transfer did not prolong the survival of third-party Brown-Norway (BN) grafts (MST 10.4±3.1 days) compared with the nontreated control group (MST 11.0±2.9 days). The potency of Ts cells purified from Ag-CsA-treated hosts to transfer unresponsiveness into normal secondary WFu hosts (MST 17.5±8.0 days) was stronger than that of Ts cells from hosts treated with CsA only (MST 10.6±2.6 days). Moreover, in vitro stimulation of monoclonal-antibody-purified Ts cells by irradiated donor Buf spleen cells potentiated the in vivo induced suppressor activity, leading to an MST of 38.1±32.6 days; indeed 3 of 12 animals (25%) displayed permanent unresponsiveness. Furthermore, Ts cells from Ag-CsA-treated hosts displayed a synergistic effect with a three-day course of CsA administration into the secondary hosts (MST 24.2±8.0 days) compared with animals only treated with CsA (MST 12.2±2.4 days, P<0.001). Moreover, the combination of the Ag-CsA regimen with Ts cells administered one day after transplantation caused even greater prolongation of graft survival (MST 34.2±14.2 days) compared with Ag-CsA-treated hosts (MST 23.2±10.2 days, P<0.025). Thus adoptively transferred antigen-specific suppressor T cells may be explored to intensify the specific immunosuppressive effect of the Ag-CaA regimen to achieve long-term unresponsiveness.