Biological Significance of Interleukin 2 Receptor Associated Molecules

Abstract

Normal T cells and adult T cell leukemia cells express two classes of interleukin 2 receptor (IL 2R), high and low affinity IL 2R (1). The growth signal seems to be delivered by interleukin 2 (IL 2) bound to only the high affinity IL 2R (2). However, the molecular and biochemical natures that determine the high and low affinity IL 2R have not been elucidated. The intracytoplasmic portion of the IL 2 binding protein is only 13 amino acids in length and is too short to mediate any kinase activity. Therefore, the mechanisms of IL 2 and IL 2R mediated growth signal transduction has been not clear. We and others (3,4) demonstrated that monoclonal antibodies that recognize molecules distinct from IL 2R and IL 2 inhibited the IL 2 dependent T cell proliferation, indicating that IL 2 dependent T cell proliferation may be complex and may require an additional signal besides binding of IL 2 to IL 2R. These data led us to investigate the possibility that molecule(s) distinct from IL 2R regulate the transmembrane signal transduction mediated by IL 2R-IL 2 interaction.