title: Proliferation of T lymphocytes in response to interleukin 2 varies with their state of activation.
abstract: The interleukin 2 (IL 2) receptor on T lymphocytes can be upregulated by a variety of stimuli including antigen, lectin, and IL 2 itself. In this report, the direct binding of radiolabeled IL 2 and a quantitative bioassay of T cell responsiveness to IL 2 were used to determine the biological significance of upregulation of the murine IL 2 receptor. Antigen and lectin, and to a lesser extent IL 2, were found to cause an increase in the expression of the high affinity form of the IL 2 receptor on both a T cell clone and concanavalin A-induced T cell blasts. A 2-day stimulation with antigen resulted in an increase in the sensitivity of the T cell clone to IL 2, whereas activation with IL 2 caused a decrease in the sensitivity of these cells to subsequent stimulation with IL 2. Comparison of the direct binding and the functional data revealed that IL 2-preactivated T cells required a greater number of occupied high affinity IL 2 receptors to achieve a given fractional response than did unactivated T cells. These observations suggest that the sensitivity with which a T cell responds to IL 2 is not determined solely by the number of high affinity IL 2 receptors it bears.
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D002999:Clone Cells; D005455:Fluorescent Antibody Technique; D007376:Interleukin-2 / Q000276:immunology*; D008213:Lymphocyte Activation; D051379:Mice; D008815:Mice, Inbred Strains; D011971:Receptors, Immunologic / Q000276:immunology; D015375:Receptors, Interleukin-2; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D007376:Interleukin-2; D011971:Receptors, Immunologic; D015375:Receptors, Interleukin-2