Interleukin-2 (IL-2) and its receptor.

The interleukin-2 (IL-2) receptor system which is responsible for T-cell cycle progression is a unique hormone-receptor system in that both the ligand and the receptor need to be induced. In the present article I will review the biological and molecular characteristics of IL-2 and its receptor, as well as the differential triggering and growth requirements that L3T4+ (T4+) helper and Lyt-2+ (T8+) cytotoxic/suppressor T-cells display to respond. The various mechanisms of regulation operating to restrain clonal IL-2-dependent expansion of normal T-lymphocytes will be discussed.