Interleukin-1 alpha (IL-1alpha) is a protein that in humans is encoded by the IL1A gene. The protein encoded by this gene is a cytokine of the interleukin-1 family. Interleukin-1 alpha possesses a wide spectrum of metabolic, physiological, haematopoietic activities, and plays one of the central roles in the regulation of the immune responses. It binds to the interleukin-1 receptor. Silver et al. (1990) showed that the mouse Il1a and Il1b genes are contained in a genomic fragment of about 70 kb. Further studies suggested that Il1b lies 5-prime to Il1a, that the 2 genes are oriented in the same direction, and that they are separated by about 50 kb.