Human suppressor T cells induced in vitro with an autologous renal allograft-derived T cell line. II. Activity and specificity of a soluble suppressor factor.

Human suppressor T cells induced by autologous mixed lymphocyte reaction (AMLR) using fresh responder PBL from a renal transplant recipient and an autologous irradiated antidonor CTL line (EE-1) established from a biopsy of the patient's own allograft were studied for the production of suppressor factors. The suppressor cell lines propagated (designated TsEE) were capable of inhibiting the in vitro generation of proliferative and cytotoxic responses of responder cells from the recipient or other individuals who shared HLA-B7 with TsEE cells, regardless of the stimulatory cell phenotype. Coculture of TsEE cells with the autologous irradiated EE-1 inducer cell line in vitro yielded a soluble factor (designated TsEEF) capable of inhibiting the generation of MLR and CTL responses, as well as mitogen-induced proliferative responses to PHA and PWM in an HLA-unrestricted manner. TsEEF also inhibited the replication of lymphoblastoid T cell lines (Molt-4 and HSB) but not B cell lines (SB and JC-EBV) or PBL stimulated with the B cell mitogen LPS. Control supernatants obtained from each of the cells used to generate TsEE in AMLR (i.e., EE-PBL and the EE-1 line) cultured alone or together for 48 hr demonstrated no suppressive activity in any of these test systems. TsEEF was nontoxic for lymphoid cells, was nondialyzable (greater than 12kDa), did not act by interfering with IL-1 or IL-2 utilization, and was negative for TNF and IFN-gamma activity. Functionally, the suppressive activity of TsEEF was dose-dependent, did not shift MLR kinetics, and could be absorbed by T cells. T cells incubated with TsEEF for 4 hr were unresponsive to subsequent mitogen or MLR stimulation. These findings indicate that, whereas T suppressor cell lines propagated from the circulation of a stable renal transplant recipient demonstrate class I HLA restriction, the activity of their soluble products is not HLA-restricted, and functionally inhibits T cell proliferation.