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Chemokine: small cytokines, including a number of secreted growth factors and interferons involved in mitogenic, chemotactic, and inflammatory activity; distinguished from other cytokines by their receptors, which are G-protein coupled receptors; divided into 4 subfamilies based on the arrangement of the two N-terminal cysteines; some members can bind multiple receptors and many chemokine receptors can bind more than one chemokine; this redundancy allows precise control in stimulating the immune system and in contributing to the homeostasis of a cell; when expressed inappropriately, chemokines play a role in autoimmune diseases, vascular irregularities, graft rejection, neoplasia, and allergies; exist as monomers, dimers and multimers, but are believed to function as monomers; found only in vertebrates and a few viruses. See CDs: Chemokine_CXC (cd00273), Chemokine_CC (cd00272), Chemokine_C (cd00271), and Chemokine_CX3C (cd00274) for chemokine subgroups.