Regulation by interleukin 2 of interleukin 2 receptors and gamma-interferon synthesis by human thymocytes: augmentation of interleukin 2 receptors by interleukin 2.
The role of interleukin 2 (IL 2) on the expression of IL 2 receptors and on the synthesis of gamma-interferon (gamma-IFN) by human thymocytes was investigated. Human thymocytes isolated from specimens obtained during cardiac surgery of infants and children were induced with one or all of the following agents: IL 2, concanavalin A (Con A), and 12-O-tetradecanoylphorbol 13-acetate (TPA). The expression of IL 2 receptors and gamma-IFN titers were determined. The results indicate that thymocytes cultured in complete medium do not express receptors for IL 2, nor did IL 2 by itself induce the expression of IL 2 receptors. Con A induced the expression of IL 2 receptors by a moderate number of the thymocyte population and induced the synthesis of low amounts of gamma-IFN. Preincubation of thymocytes with TPA increased the response to Con A; both the number of thymocytes expressing receptors and the synthesis of gamma-IFN were increased. Addition of IL 2 to these cultures further augmented the expression of IL 2 receptors and gamma-IFN synthesis and resulted in the optimal expression of IL 2 receptors and maximal gamma-IFN synthesis. The expression of IL 2 receptors could be detected within 24 hr and preceded the induction of proliferation; it was therefore probably not due to the clonal expansion of a population of receptor-bearing thymocytes. Conversely, inhibition of IL 2 synthesis with dexamethasone (Dex) by thymocytes activated with Con A, or inhibition of the function of IL 2 receptors by anti-Tac, resulted in a decrease in the number of IL 2 receptor-bearing thymocytes activated with Con A, or inhibition of the function of IL 2 receptors by anti-Tac, resulted in a decrease in the number of IL 2 receptor-bearing thymocytes and of gamma-IFN synthesis. Thymocytes activated with TPA and Con A were more resistant to the inhibitory effects of Dex on the expression of IL 2 receptors than thymocytes activated with Con A alone. Maximal inhibition of the expression of IL 2 receptors and of gamma-IFN synthesis was achieved as a result of the synergistic effect of anti-Tac with Dex. Therefore, when IL 2 was prevented from binding to the receptors, and IL 2 synthesis was inhibited, the number of thymocytes expressing IL 2 receptors was sharply reduced and gamma-IFN synthesis was markedly inhibited.(ABSTRACT TRUNCATED AT 400 WORDS)
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D000276:Adjuvants, Immunologic / Q000502:physiology*; D000911:Antibodies, Monoclonal / Q000502:physiology; D000954:Antigens, Surface / Q000276:immunology; D002648:Child; D003208:Concanavalin A / Q000494:pharmacology; D003524:Cyclosporins / Q000494:pharmacology; D003907:Dexamethasone / Q000494:pharmacology; D004357:Drug Synergism; D006801:Humans; D007223:Infant; D007371:Interferon-gamma / Q000096:biosynthesis*; D007376:Interleukin-2 / Q000502:physiology*; D008213:Lymphocyte Activation / Q000187:drug effects; D011971:Receptors, Immunologic / Q000096:biosynthesis*; D015375:Receptors, Interleukin-2; D013601:T-Lymphocytes / Q000378:metabolism*; D018127:Tumor Necrosis Factor Receptor Superfamily, Member 7
D000276:Adjuvants, Immunologic; D000911:Antibodies, Monoclonal; D000954:Antigens, Surface; D003524:Cyclosporins; D007376:Interleukin-2; D011971:Receptors, Immunologic; D015375:Receptors, Interleukin-2; D018127:Tumor Necrosis Factor Receptor Superfamily, Member 7; D003208:Concanavalin A; D003907:Dexamethasone; D007371:Interferon-gamma