Substance

Function in Inflammation

Source

Histamine

Vasodilation; increased permeability of capillaries; conversion of an inactive plasma protein (kininogen) into active peptides called kinins; released early in inflammation

Mast cells, basophils, platelets

Kinins (e.g., bradykinin)

Vasodilation and increased permeability of capillaries; increase production of CAMs; stimulate sensory pain receptors

Plasma protein produced by the liver and other cells as kininogen; activated by tissue injury

Leukotrienes (slow-reacting substance of anaphylaxis [SRS-A])

Effects similar to histamine; released later in the inflammatory response than histamine and longer lasting

Eicosanoids produced from arachidonic acid molecules of mast cell and basophil plasma membranes

Prostaglandins

Vasodilation, fever, stimulate sensory pain receptors (categories include E, D, A, F, and B)

Eicosanoids produced from arachidonic acid molecules of mast cell and basophil plasma membranes

Chemotactic factor

Attracts immune cells; release of specific chemotactic factors attract a specific type of cell (e.g., neutrophil chemotactic factor attracts neutrophils early in the inflammatory response; with a parasitic infection, eosinophil chemotactic factor attracts eosinophils)

Mast cells and basophils

Serotonin

Effects similar to histamine

Platelets

Nitric oxide

Vasodilation; may inhibit mast cells and platelets

Endothelium of blood vessels

Alpha-1 antitrypsin

Inhibits damage to connective tissue by enzymes released from destroyed phagocytes

Plasma protein formed by the liver

C-reactive protein

Activates complement by binding to polysaccharides on bacteria surface

Liver

IL-1 and TNF-α

Increase cell-adhesion molecules (CAMs) to cause margination; cause endothelial cell contraction to facilitate diapedesis