Abstract
Conditioned medium from Ag-specific suppressor T cell hybridomas contains soluble factors (TsF) that modulate immune responses in an Ag-specific manner. We previously generated a series of TCR-alpha- and TCR-beta- expression variants from a 4-hydroxy-3-nitrophenyl acetyl (NP)-specific inducer suppressor T cell hybridoma and demonstrated that loss of TCR alpha-chain mRNA, but not TCR-beta chain mRNA, was accompanied by concomitant loss of suppressor bioactivity. Suppressor factor bioactivity was restored by expression of TCR alpha-chain cDNA, suggesting that the TCR alpha-chain plays a critical role in Ag-specific suppressor cell function. We have now transfected TCR alpha-chain from a Th cell clone specific for arsanylated peptides plus I-Ad into a TCR-alpha- derivative of an NP-specific inducer suppressor T cell hybridoma. The transfectants expressed a new hybrid TCR-alpha beta complex and produced soluble factors that suppressed azobenzenearsonate hapten (ABA) but not NP delayed-type hypersensitivity responses. These supernatants mediated suppression of the induction, but not the effector phase of the delayed-type hypersensitivity reaction. In reciprocal experiments we transfected a TCR alpha-chain from an NP-specific suppressor T cell hybridoma into a TCR-alpha- hybridoma derived from the ABA-specific Th cell hybridoma. The NP-specific TCR alpha-chain was expressed in the Th cell hybridoma, but the supernatant from this transfectant did not suppress DTH responses to either NP or ABA. However, the latter supernatants, when combined with cell lysates derived from a TCR-alpha- Ts hybridoma, specifically suppress NP DTH responses. These data are consistent with the interpretation that TCR alpha-chain imparts Ag specificity to the suppressor molecule and a second, yet undefined, component produced by the Ts hybridoma controls the immunoregulatory bioactivity.
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