Interleukins are a broad class of biologically active proteins with hormone‐like actions that regulate the development, differentiation and functions of cells of the immune and haematopoietic systems. The activities of interleukins are mediated via cell surface receptors.

The proinflammatory and immune‐stimulatory activities of interleukins are essential for host defence against pathogens.​ The biological properties of interleukins have suggested their potential for development as therapeutic drugs (biopharmaceuticals) against infections and chronic diseases, such as cancer. Antibody and receptor antagonists of interleukins are showing promise for the treatment of autoinflammatory and autoimmune diseases.