ABSTRACT
Elucidation of the structures of interleukin-2 (IL-2) receptors has led to a greater understanding of their roles in the activation of nonspecific cytotoxicity. The human T cell immune response is an extremely complex process involving multiple levels of regulation. When normal resting T cells are stimulated by an antigen or mitogenic lectin, a subpopulation of T cells is stimulated to synthesize and secrete the 15,500-D polypeptide hormone IL-2, which is not produced by unstimulated cells. High- and low-affinity receptors are usually expressed in approximately a 1 to 10 ratio, but only the high-affinity receptors are capable of internalizing IL-2 and transducing the mitogenic signal. The identification of p70 as an IL-2 binding protein and a subunit of the high-affinity IL-2 receptor suggested the possibility that p70 itself may be an IL-2 receptor involved in lymphokine activated killer induction.
