IL-1α is a member of interleukin 1 family. IL-1α and IL-1β recognize the same IL-1 receptor and share a number of similar biological functions. IL-1α is predominantly a cell-associated molecule whereas IL-1β is a secreted molecule.

IL-1α is synthesized primarily as a 31 kDa precursor that lacks a signal peptide. Cleavage of the precursor is via the cysteine protease calpain, resulting in a 17.5 kDa mature IL-1 molecule. Being active in the processed form, the IL-1 precursor is also biologically active via specific cell binding. A portion of the precursor is transported to the cell surface and associated with the cell membrane. Precursor IL-1α can be released and cleaved by extracellular proteases when the cells die, and can also be cleaved by activation of the calcium-dependent, membrane-associated calpains.