Cytokines (CK) are small molecule peptides or glycoproteins synthesized and secreted by various tissue cells (mainly immune cells). Cytokines can mediate intercellular interactions and have various biological functions, such as regulating cell growth, differentiation and maturation, maintaining function, regulating immune response, participating in inflammatory response, wound healing, and tumor growth and decline. Initially, people were unclear about the nature of cytokines and named them based on their biological activity, resulting in multiple names for the same cytokine. Later, people realized that cytokines are mainly synthesized by white blood cells and mainly mediate interactions between white blood cells. Therefore, these factors were uniformly named interleukin (IL), and were named with Arabic numerals in the order of discovery, such as IL-l, IL-2, IL-3, etc. Since the discovery of interferon by Lssac in 1957, over 200 cytokines have been discovered so far. People collectively refer to all interleukins, interferons, tumor necrosis factors, hematopoietic factors, growth factors, chemokines, etc. as cytokines.
