Characterization of interleukin-15 (IL-15) and the IL-15 receptor complex

IL-15 interacts with a heterotrimeric receptor that consists of the and subunits of the IL-2 receptor (IL-2R) as well as a specific, high-affinity IL-15-binding subunit, which is designated IL-15R. Since both the and the subunits of the IL-2R are required for signaling by either IL-2 or IL-15, it is not surprising that these cytokines share many activitiesin vitro. However, the differential expression of these cytokines and the chains of their receptors within various tissues and cell types suggests that IL-2 and IL-15 may perform at least partially distinct physiological functions. The production of IL-15 by macrophages, and possibly other cell types, in response to environmental stimuli and infectious agents suggests that IL-15 may play a role in protective immune responses, allograft rejection, and the pathogenesis of autoimmune diseases.