Abstract
Interleukin 1 (IL-1) is the major immunoregulatory molecule produced by macrophages and other related cells. It acts as the molecular orchestrator of nonspecific host defense mechanisms against multifarious insults. In this study we report the characterization of an IL-1-like protein from the starfish Asterias forbesi. IL-1-like activity was found in the coelomocytes of this invertebrate and was also isolated and purified from the coelomic fluid. The coelomocytes were capable of phagocytosing latex particles and were adherent to plastic tissue culture dishes. Starfish IL-1 stimulated murine thymocyte proliferation directly and to a greater degree in the presence of submitogenic concentrations of concanavalin A. Starfish IL-1 also stimulated fibroblast proliferation and fibroblast protein synthesis. It was found to have a Mr of 29,500 and pI values of 7.5, 5.9, and 4.8. Starfish IL-1 activity was inhibited by an antibody to human IL-1. These characteristics suggest starfish IL-1 to be very similar to murine and human IL-1. The similarities to vertebrate IL-1 considered along with the evolutionary position of the starfish suggest that IL-1 is an important, ancient, and functionally conserved molecule.