The Interleukin-2 Receptor on Normal and Malignant Lymphocytes

Abstract

The induction of a T-cell immune response to a foreign antigen requires the activation of T lymphocytes with receptors for the specific antigen. The human antigen-specific T-cell receptor has been shown to be a polymorphic heterodimer of α and β chains of approximately 40–50 Kd associated with three or four 20- to 28-Kd nonpolymorphic polypeptide chains identified by the T3 monoclonal antibody (1–6). T-cell activation is initiated following the interaction of antigens, mitogens, or antibodies with this complex antigen-specific T-cell receptor. First, after the interaction with antigen presented in the context of products of a major histocompatibility locus and the macrophage-derived interleukin-1, T cells express the gene encoding the lymphokine interleukin-2 (IL-2), previously termed T-cell growth factor (7,8). To exert its biological effect, IL-2 must interact with specific high-affinity membrane receptors. Resting T cells do not express IL-2 receptors, but receptors are rapidly expressed on T cells after activation with an antigen or mitogen (9–11). Thus, but after activation the genes for both proteins become expressed. A failure of the production of either the growth factor or its receptor results in failure of the T-cell immune response. Thus, both the production of IL-2 and the display of IL-2 receptors are pivotal events in the full expression of the T-cell immune response. Although the interaction of appropriately presented antigen with its specific polymorphic receptor complex confers specificity for a given immune response, the interaction of IL-2 with IL-2 receptors determines its magnitude and duration.