Chemokines in inflammatory bowel disease.

C hemokines (chemotactic cytokines) are small (7–10 kDa) heparin binding proteins that govern the migration of circulating leucocytes to the sites of inflammation. Chemokines, currently numbering more than 50, are classified into four supergene families based on cysteine residues: CXC, CC, C, and CX3C chemokines (table 1). Chemokines are distinguished from other cytokines by acting on the G protein coupled serpentine receptors. Chemokines are classified into constitutively secreted and inducible. Those that are constitutively secreted are homeostatic chemokines directing basal leucocyte trafficking and the organisation of the lymphoid tissue. Inducible chemokines are inflammatory molecules responsible for mediating the recruitment of leucocyte effector populations to the sites of immune reaction and tissue injury.