Ligand-induced desensitization of interleukin 1 receptor-initiated intracellular signaling events in T helper lymphocytes.

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Abstract
Although interleukin 1 (IL-1) receptor signaling events in T helper lymphocytes are incompletely characterized, events associated with translocation of the transcription factor NF-kappa B are receptor-proximal assays of ligand-initiated responses. In this report we demonstrate that the transient nature of IL-1-induced NF-kappa B nuclear translocation occurs as a consequence of ligand-induced receptor desensitization. Other receptor-initiated events including induction of I kappa B alpha phosphorylation, expression of c-jun and junB mRNA, and costimulatory effects on IL-2 synthesis also are altered by IL-1 receptor desensitization. IL-1 receptor desensitization is not initiated by tumor necrosis factor, which also stimulates NF-kappa B translocation, and is not a consequence of alterations in either IL-1 receptor expression or binding affinity. In the absence of IL-1, the effects of desensitization are completely reversed within 18 h. Since IL-1 desensitization is initiated under conditions of low receptor occupancy, it is likely that receptor desensitization results from alterations to a receptor-proximal transducer, rather than from direct modification of the IL-1 receptor. These results suggest that the cyclic nature of the events in the T helper lymphocyte activation program can be controlled, in part, by the reversible desensitization of cell surface IL-1 receptors.