These soluble glycoproteins and peptides are released from living cells such as mocrophages and lymphocytes in response to noxious stimuli such as ischemia, endotoxin, physical and chemical injury. They may be conviently subdivided into pro and anti- inflammatory cytokines.
Pro-inflammatory cytokines are predominantly released by macrophages and up regulate inflammatory reactions. Anti-inflammatory cytokines are predominantly released by T lymphocytes and are involved with down regulating the inflammatory response. Transforming growth factor has both pro and anti inflammatory effects.