Interleukin 1 (IL-1) is an interleukin that acts as both a pro-inflammatory cytokine and an anti-inflammatory myokine. IL-1 is a pleiotropic cytokine involved in a variety of immune responses, inflammatory processes and hematopoietic processes. Il-1 stimulates thymus cell proliferation by inducing il-2 release, b cell maturation and proliferation, and fibroblast growth factor activity.