In this issue of Blood, Bergamaschi and colleagues demonstrate that effectively all circulating IL-15 found in the serum of humans and mice is associated with the soluble IL-15Rα.(1)

Human neutrophils have been shown recently to express both the beta and the gamma chains of the interleukin-2 receptor (IL-2R). IL-15, a cytokine that has recently been cloned and characterized, was found to share many of the biological functions of IL-2 and is known to mediate signals through IL-2R beta and IL-2R gamma. In recent studies, we observed that IL-2 exerts few effects on various neu...