The interleukin-1 receptor antagonist (IL-1RA) is a protein that in humans is encoded by the IL1RN gene. IL-1RA was initially called the IL-1 inhibitor and was discovered separately in 1984 by two independent laboratories.IL-1RA, is an agent that binds non-productively to the cell surface interleukin-1 receptor (IL-1R). IL-1R is the same receptor that binds interleukin 1 (IL-1). Hence IL-1RA prevents IL-1 from sending a signal to that cell. IL-1RA is a member of the interleukin 1 cytokine family. IL1Ra is secreted by various types of cells including immune cells, epithelial cells, and adipocytes, and is a natural inhibitor of the pro-inflammatory effect of IL1β.