Role of self carriers in the immune response and tolerance. VI. Induction and reversal of TNP-modified self unresponsiveness in vitro.

Abstract

The involvement of T-suppressor cells in hapten-modified self unresponsiveness induced in vivo is well established. However, TNP-modified syngeneic spleen cells (TNP-SC) can block the anti-TNP PFC response of normal or nude spleen cells to TNP-immunogen in vitro, an effect that is apparently T cell-independent. In this study, we have used a 2-stage culture system in which both the induction of tolerance by irradiated syngeneic TNP-SC and the subsequent challenge with TNP-immunogen take place in vitro to dissect the cellular events that lead to unresponsiveness. Our results show that not only are spleen cells precultured with TNP-SC tolerant to challenge, but that these cells are able to specifically suppress the response of freshly prepared normal spleen cells to the T-independent antigens TNP-POL or TNP-LPS. Irradiation of the precultured cells abrogates the suppressor activity and rules out hapten carryover as the mechanism of suppression. Suppressor cells were able to inhibit the response of anti-Ba theta and C-treated spleen cells, suggesting that suppressor function is directed toward the B cell and/or accessory cells. Anti-Ba theta and C treatment of spleen cells before preculture with TNP-SC prevented the induction of both tolerance and suppression. Nylon wool-enriched T cells, on the other hand, could generate suppressor cells in response to TNP-SC. These results demonstrate that, like the in vivo situation, T cells are involved in the generation of this form of B cell tolerance in vitro. Implications relevant to the mechanisms of tolerance induction are discussed.