cytokine

1. (biochemistry, immunology) Any of various small regulatory proteins that regulate the cells of the immune system.Examples: "Thus, in the case of viral infection, mechanisms of resistance would be threefold, namely, interferon production, the immune response, including both antibody and lymphokine production, and the generation of lymphokine-like substances by the infected cells themselves. These latter substances have been defined as cytokines."; "A fundamental feature expressed by the vast majority of cytokines is a profound immunomodulatory activity. Many cytokines, presently available in pure recombinant form, modify bone cell metabolism."; "The cytokines are generally considered to be a group of peptides secreted by cells of the immune system such as macrophages, lymphocytes and T cells, although the same peptides may also be secreted by non-immune cells such as neurological tissues and adipocytes."