Generation and characterization of a continuous line of CD8+ suppressively regulatory T lymphocytes which down-regulates experimental autoimmune orchitis (EAO) in mice.

We have previously shown that two injections with viable syngeneic testicular germ cells (TC) alone developed experimental autoimmune orchitis (EAO) in C3H/He mice, and that the induction of antigen-specific tolerance in this EAO model is associated with the generation of antigen-specific suppressively regulatory T (Ts) cells. For the elucidation of the nature of these Ts cells, a murine Ts cell line (designated Ts-A) was established. This line was generated from the spleen cells of C3H/He mice which had received three i.v. injections of a soluble (deaggregated) form of murine testicular antigen (mTA), followed by the repeated selection of these spleen lymphocytes in vitro by stimulation with mTA. Adoptive transfer of Ts-A cells into naive syngeneic mice immediately before the first TC injection was found to downgrade EAO in actively immunized recipients. The transferred Ts-A cells significantly inhibited the cellular immune response to TC in the recipients in an antigen-specific manner, but these cells had no inhibitory effect on the humoral immune response to TC. This line could also inhibit in vitro syngeneic TC-driven proliferation of orchitogenic lymphocytes. Surface phenotype of this line was CD8+, CD4-, Thy-1.2+, CD3+, and TCR alpha beta+. These findings may suggest an in vivo role for suppressively regulatory lymphocytes, capable of inhibiting helper T cells, in the regulation of EAO.