Interleukin-1 (IL-1) is one of the first cytokines ever described. Its initial discovery was as a factor that could induce fever, control lymphocytes, increase the number of bone marrow cells and cause degeneration of bone joints. At this time, IL-1 was known under several other names including endogenous pyrogen, lymphocyte activating factor, haemopoetin-1 and mononuclear cell factor, amongst others.

It was around 1984-1985 when scientists confirmed that IL-1 was actually composed of two distinct proteins, now called IL-1α and IL-1β.These belong to a family of cytokines known as the interleukin-1 superfamily.Both IL-1α and IL-1β are produced by macrophages, monocytes and dendritic cells.