The role of suppressor T cells in the expression of immune response gene function

Mechanisms underlying major histocompatibility complex (MHC)-linked immune response (Ir) gene regulation of immune responses have been the subject of considerable interest and debate in recent years. Two general mechanisms have been proposed to account for antigen-specific, Ir gene-mediated unresponsiveness. In one, defective antigen presentation resulted from the failure of processed nominal antigen and Ia antigen to associate on the antigen presenting cell membrane in a manner sufficient for helper T cell (Th cell) activation. By contrast, it has been proposed that selected Th cell clones were deleted from the repertoire during ontogeny or otherwise rendered unresponsive to the antigen-Ia complex, i.e., functionally deleted. Either of these mechanisms would account for the deficient activation of antigen-specific, Th cells observed in genetic low or nonresponder mice. In addition, the failure of mice to respond to certain antigens under Ir gene control has been attributed to the activation of specific suppressor T (Ts) cells. The latter mechanism might be considered a corollary or subset of the clonal deletion model. However, an important distinction exists. In the case of active, Ts cell-mediated Ir gene regulation, genetic low responder animals should retain the capacity for antigen-induced activation of Th cells, or Th cell activity should be demonstrable in these mice. In this communication, experiments are described which are designed to evaluate the possibility that active Ts cell-mediated regulatory mechanisms were of general importance in mediating Ir gene-related unresponsiveness.(ABSTRACT TRUNCATED AT 250 WORDS)