Inflammation: A basic way in which the body reacts to infection, irritation or other injury, the key feature being redness, warmth, swelling and pain. Inflammation is now recognized as a type of nonspecific immune response.

More information: In technical terms, the inflammatory response directs immune system components to the site of injury or infection and is manifest by increased blood supply and vascular permeability which, in technical terms, allows chemotactic peptides, neutrophils, and mononuclear cells to leave the intravascular compartment. Microorganisms are engulfed by phagocytic cells (e.g., neutrophils and macrophages) in an attempt to contain the infection in a small-tissue space. The response includes attraction of phagocytes in a chemotactic gradient of microbial products, movement of the phagocyte to the inflammatory site and contact with the organism, phagocytosis (ingestion) of the organism, development of an oxidative burst directed toward the organism, fusion of the phagosome and lysosome with degranulation of lysosomal contents, and death and degradation of the organism. When quantitative or qualitative defects in neutrophil function result in infection, the infection usually is prolonged and recurrent and responds slowly to antimicrobial agents. Staphylococci, gram-negative organisms, and fungi are the usual pathogens responsible for these infections.