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A Single Major Pathway of T‐Lymphocyte Interactions in Antigen‐Specific Immune Suppression

Two major facts about T lymphocytes have become apparent over the past 20 years: first, as demonstrated by the early work of Claman & Chaperon [10], Davies [13] and Miller & Mitchell [36] for helper function and Gershon [28] for suppressor function in humoral responses, a key activity of T cells is to serve as regulators of immunity; second, as initially described by Cantor, Boyse and associates [6,9], the peripheral T-cell pool is very heterogeneous, consisting of a large number of subsets, each with distinct differentiation naarkers and immunologic functions. Intensive investigation of the regulatory phenomenon of specific immune suppression has revealed the importance of multiple interactions among these T-cell subsets in even this limited aspect of cellular immune responses [1, 17, 20, 26, 35, 45, 50, 52, 63, 65, 67]. During the course of these studies, several distinct model systems have been used to examine T-cell-mediated suppression, and, as a result, several related but clearly nonidentical suppressor regulatory pathways consisting of a variety of T-T interactions have been described, involving cells with different phenotypes and soluble suppressor factors with various immunochemical and biological properties. These data raise the important question as to whether there are many different pathways of T-cell-mediated suppression, or whether the described pathways are fragments of a larger single sequence. During the past several years, these laboratories have studied in detail several different suppressor T-cell (Ts) models involving both humoral and cell-mediated immunity [26, 45, 50, 65, 67] in an effort to define the molecular basis of antigen-specific T-cell recognition and cell-cell communication. Recent findings in these systems have suggested to us the possibility of integrating the great majority of results on T-cell suppression into a single overall scheme that eliminates many key differences between the several model systems. This review is an attempt to summarize briefiy the best-defined systems of immune suppression and to suggest an integration of these data into a major suppressor pathway.