One of a group of related proteins made by leukocytes (white blood cells) and other cells in the body. Interleukin-1-alpha, one form of interleukin-1, is made mainly by one type of white blood cell, the macrophage, and helps another type of white blood cell, the lymphocyte, fight infections. It also helps leukocytes pass through blood vessel walls to sites of infection and causes fever by affecting areas of the brain that control body temperature. The other form of interleukin-1, interleukin-1-beta, acts the same as interleukin-1-alpha. Interleukin-1-alpha made in the laboratory is used as a biological response modifier to boost the immune system in cancer therapy. Interleukin-1-alpha is a type of cytokine.