Structure and Function of the Human Interleukin-2 Receptor

Abstract

Clonal expansion of resting T cells requires the sequential stimulation of two sets of glycoproteins: the T cell receptor (T3-Ti) complex and the interleukin-2 receptor (IL-2R) complex. The human T3-Ti complex is composed of two components: a polymorphic heterodimer of α and β chains, which determine both antigen specificity and major histocompatibility complex (MHC) restriction, and a complex of nonpolymorphic molecules called T3-γ, -δ and -e, which may play a role in transducing the T-cell activation signal (Meuer et al. 1984). Triggering of the T3-Ti complex induces expression of the genes for interleukin-2 (IL-2), a T cell growth factor, and its receptor (IL-2R). The net effect is therefore that clonal expansion of T cells occurs by converting the signal generated upon specific antigen: MHC/T3-Ti interaction into a mitogenic signal mediated by IL-2 and IL-2R (see Fig. 1). The molecular nature of the IL-2 system has been studied in detail (reviewed by Taniguchi et al. 1986). In this review, we describe the main features of the human IL-2R or IL-2R complex.