IL-1-alpha. A type of biological response modifier (a substance that can improve the body's natural response to infection and disease). Interleukin-1-alpha stimulates the growth and action of immune system cells that fight disease. Interleukin-1-alpha is normally produced by the body, but it can also be made in the laboratory. Also called IL-1-alpha, interleukin-1-alfa, and IL-1-alfa.