Identification of a Novel Interleukin-2 Receptor Subunit

Abstract

Interleukin-2 (IL2) binds to both high (K_d = 10–30 pM) and low (K_d = 10–30 nM) affinity IL2 receptors on activated T lymphocytes (1,2). Both classes of receptors share reactivity with anti-Tac monoclonal antibody and therefore contain the “Tac antigen” or 55 kD IL2 binding protein (3,4). The high affinity receptors account for approximately ten percent of the total number of receptors on activated T cells (2). It is generally believed that the high affinity receptors mediate the growth and differentiation effects of IL2, although the contribution, if any, of low affinity sites to such effects has not been as carefully examined. Only the high affinity sites undergo receptor mediated endocytosis after the binding of IL2 (5,6). The molecular basis for the distinction between the different classes of receptors has been unclear heretofore, and this short report will summarize the data from our laboratory, some of which has been published (7).