Chemokines and chemokine receptors in infectious diseases

Today, 10 years after the discovery of IL-8, chemokines (chemotactic cytoki nes) are seen as the stimuli that largely control leucocyte migration. Chem okines are low molecular weight chemoattractant cytokines secreted by a var iety of cells, including leucocytes, epithelial cells, endothelial cells, f ibroblasts and numerous other cell types. They are produced in response to exogenous stimuli, such as viruses and bacterial LPS, and endogenous stimul i, such as IL-1, TNF and IFN. These factors mediate chemotaxis and leucocyt e activation. They also regulate leucocyte extravasation from the blood and /or lymph vessel luminal surface to the tissue space, the site of inflammat ion. There is no doubt that chemokines and chemokine receptors are critical for defence against infectious pathogens. It is also clear that these path ogens have evolved to accommodate the workings of the host immune system. S urvival of these infectious agents appears dependent upon strategies that c an evade, suppress, counteract or otherwise confound the constellation of h ost responses to invading pathogens. In this regard, the chemokines and the ir receptors are a major target. Reviewed in the present paper are several examples in which microbial pathogens have usurped the mammalian chemokine system to subvert the host immune response.