Chemokine regulation of normal and pathologic immune responses.

Chemokines are small basic proteins that are the major mediators of all leukocyte migration. There are at least 46 distinct chemokines, and 19 chemokine receptors, making it easily the largest cytokine family. Chemokines can be both beneficial and harmful, by either stimulating an appropriate immune response to microbial invasion, or by mediating pathologic tissue destruction in many types of human disease. Chemokines have been implicated in the tissue destruction seen in autoimmune diseases, atherosclerosis, allograft rejection, and neoplasia. Chemokines also play essential roles in normal lymphocyte trafficking to primary and secondary lymphoid organs for antigen presentation and lymphocyte maturation. Chemokines also regulate hematopoietic stem and progenitor cell homing and proliferation. Therefore, it is likely that chemokines will become important targets for pharmacologic intervention in a wide variety of human diseases in the future.