Chemokines, a family of chemotactic cytokines

Chemokines are low-molecular-weight proteins that stimulate recruitment of leukocytes. They are secondary pro-inflammatory mediators that are induced by primary pro-inflammatory mediators such as interleukin-1 (IL-1) or tumor necrosis factor (TNF). The physiologic importance of this family of mediators is derived from their specificity. Unlike the classic leukocyte chemo-attractants, which have little specificity, members of the chemokine family induce recruitment of well-defined leukocyte subsets. Thus, chemokine expression can account for the presence of different types of leukocytes observed in various normal or pathologic states. There are two major chemokine sub-families based upon the position of cysteine residues, i.e., CXC and CC. All members of the CXC chemokine sub-family have an intervening amino acid between the first two cysteines; members of the CC chemokine sub-family have two adjacent cysteines. As a general rule (with some notable exceptions), members of the CXC chemokines are chemotactic for neutrophils, and CC chemokines are chemotactic for monocytes and a small sub-set of lymphocytes. This review discusses the potential role of chemokines in inflammation and focuses on the two best-characterized chemokines, monocyte chemoattractant protein-1 (MCP-1), a CC chemokine, and interleukin-8 (IL-8), a member of the CXC chemokine sub-family.