Recent advances in the biochemical and genetic analysis of soluble immunoregulatory molecules (TsF) have been achieved via the establishment of cloned TsF-producing T cell hybridomas. However, studies on in vivo regulation of immune responses have been hampered by the lack of clonal populations of nontransformed suppressor T cells (Ts). Nonhybridoma Ts clones would allow cellular dissection of complex Ts circuits and precise analyses of Ts effector mechanisms. Our laboratory has recently demonstrated that poly(Glu60Ala30Tyr10) (GAT)-specific unresponsiveness is induced in adult responder mice tolerized via the intravenous injection of GAT-coupled syngeneic spleen cells (GAT-SP). This unresponsiveness is mediated by two antigen-specific mechanisms--nontransferable clone inhibition and induction of transferable Ts which regulate both humoral and T cell-mediated delayed-type hypersensitivity (DTH) responses. We have thus applied methodology used for the production and maintenance of antigen-specific T helper (Th) clones in an attempt to establish and characterize Ts clones mediating GAT-specific in vivo suppressive activity. Therefore, spleen cells from GAT-SP tolerant responder mice were maintained in continuous culture with soluble GAT, 10% concanavalin A-conditioned medium (IL-2), and irradiated syngeneic antigen presenting cells (APC). A stable, long-term Ts cell line (J372) was isolated by this procedure. This line and one of its clones (J372.2) suppressed the afferent (induction), but not efferent (elicitation) phase of GAT-specific DTH. In contrast, the J372.2 Ts clone had no inhibitory effect on the development of specific T cell proliferative responses. Intravenous injection of small numbers (2-5 x 10(6)) of J372.2 Ts cells resulted in significant suppression of DTH responses in GAT-primed, but not in ovalbumin- or methylated bovine serum albumin-primed recipients, demonstrating the antigen-specificity of the suppression. Intravenous injection of a GAT-specific Th clone (JTL-E1) or of a DNP-specific Th line (JTL-DNP) had no suppressive effects on GAT-specific responses suggesting that J372.2-mediated unresponsiveness is the result of active suppression, and not the result of nonspecific inhibitory effects of activated T cells. More importantly, normal GAT-specific DTH responses in recipients of the JTL-E1 Th clone (maintained in the same GAT concentration as J372.2) indicated that J372.2-mediated suppression was not due to induction of nontransferable tolerance by surface-associated GAT.(ABSTRACT TRUNCATED AT 400 WORDS)