CCL4/MIP-1 beta is a beta chemokine that is secreted at sites of inflammation by activated leukocytes, lymphocytes, vascular endothelial cells, and pulmonary smooth muscle cells. It attracts a variety of immune cells to sites of microbial infection as well as to other pathologic inflammation such as allergic asthma and ischemic myocardium. CCL4 is secreted from activated monocytes as a heterodimer with CCL3/MIP-1 alpha. It signals through CCR5, and an N-terminally trimmed form additionally interacts with CCR1 and CCR2. In humans, the ability of CCL4 to bind CCR5 inhibits the cellular entry of M-tropic HIV-1 which utilizes CCR5 as a coreceptor.