CHARACTERIZATION OF INTERLEUKIN-15 (IL-15) AND THE IL-15 RECEPTOR COMPLEX

IL-15 interacts with a heterotrimeric receptor that consists of the be ta and gamma subunits of the IL-2 receptor (IL-2R) as well as a specif ic. high-affinity IL-15-binding subunit, which is designated IL-15R al pha. Since both the beta and the gamma subunits of the IL-2R are requi red for signaling by either IL-2 or IL-15, it is not surprising that t hese cytokines share many activities in vitro. However, the differenti al expression of these cytokines and the alpha chains of their recepto rs within various tissues and cell types suggests that IL-2 and IL-15 may perform at least partially distinct physiological functions. The p roduction of IL-15 by macrophages, and possibly other cell types, in r esponse to environmental stimuli and infectious agents suggests that I L-15 may play a role in protective immune responses, allograft rejecti on, and the pathogenesis of autoimmune diseases.