IL1A and infection: However, given the striking diversity of proteases (which includes intracellular, extracellular, microbial and allergen-derived sources) that can process and activate IL-1 family members, an alternative possibility is that this cytokine family has evolved specifically to serve as sentinels for aberrant protease activity that is frequently associated with infectious agents or liberated by barrier tissues or cells of the innate immune system in response to infection or tissue damage (11).