Functional responses and apoptosis of CD25 (IL-2R alpha)-deficient T cells expressing a transgenic antigen receptor.
IL-2 was initially defined as a T lymphocyte growth factor, but recent studies have provided evidence that it may also play a role in regulating T cell differentiation, apoptosis, and tolerance. To examine the contribution of IL-2 to these processes, we have bred a class II-restricted TCR transgene into mice deficient in the alpha-chain of the IL-2R, CD25. We show that in response to Ag, T cells from these mice are unable to use IL-2 and, as a result, are less efficient at traversing the cell cycle, and proliferate less than wild-type cells. Furthermore, CD25 -/- T cells exhibit reduced survival in vitro, even in the presence of costimulatory signals. IL-4 and IL-15, a cytokine related to IL-2, enhance the survival and Ag-induced proliferation of CD25 -/- T cells. Activated CD25 -/- T cells are resistant to Fas-mediated activation-induced cell death (AICD), and this defect cannot be corrected by other cytokines. Therefore, IL-2 plays a unique role in regulating AICD, but has redundant roles in T cell survival and proliferation in vitro. The failure of AICD observed with CD25 -/- T cells may explain the unexpected observation that deficiency of IL-2 or of the alpha- or beta-chain of the IL-2R results not in immunodeficiency, but in autoimmune disease.
Van Parijs
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Department of Pathology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA.
Biuckians
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Ibragimov
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Willerford
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D000818:Animals; D017209:Apoptosis / Q000235:genetics / Q000276:immunology*; D051379:Mice; D008822:Mice, Transgenic; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000235:genetics / Q000276:immunology*; D015375:Receptors, Interleukin-2 / Q000172:deficiency* / Q000235:genetics / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology* / Q000473:pathology
D016693:Receptors, Antigen, T-Cell, alpha-beta; D015375:Receptors, Interleukin-2