Chemokine receptor dimerization: two are better than one

The chemokines participate in an exceptional range of physiological and pat hological processes, including the control of lymphocyte trafficking, tumor growth, wound healing, allograft rejection, regulation of T-cell different iation, asthma, infection with HIV and atherosclerosis. This vast array of activities is triggered by the interaction of nearly 50 different chemokine s with a relatively modest number of 20 G-protein-coupled receptors. The as ymmetry between the number of receptors and ligands suggests an underlying, shared control mechanism activated at a very early stage of the response. One of the first events triggered by the binding of chemokines is the homo- and heterodimerization of their receptors; here, we outline these events a nd their consequences in chemokine signaling.