Mice inoculated i.v. with superantigens exhibit long lived Ag-specific T cell tolerance. An in vitro model for this phenomenon is the ensuing unresponsiveness of Th1 T cell clones activated via the TCR/CD3 complex in the absence of co-stimulation. We have previously demonstrated alterations in TCR-mediated early protein tyrosine phosphorylation events in Th1 clones anergic for IL-2 production. In this study, we demonstrate unresponsiveness in CD4+ and CD8+ T cells from V beta 8.1 transgenic mice inoculated i.v. with the superantigen Mls-1a. The unresponsiveness of both CD4+ and CD8+ T cells involves defective IL-2 production upon restimulation, with CD4+ T cells exhibiting an additional defect in IL-2 utilization. The transgenic model allowed study of T cell signaling in a relatively homogeneous population of unresponsive cells without elaborate purification of Ag-reactive populations. Both CD4+ and CD8+ T cells exhibit altered tyrosine phosphorylation of two protein substrates upon CD3-mediated restimulation. The substrates involved, p38 and p75, are of identical size to substrates similarly affected in anergic Th1 clones. Altered tyrosine phosphorylation is therefore closely associated with defective IL-2 production in these three anergic T cell types, and may play a role in the maintenance of anergy.

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