C-C motif chemokine 5(CCL5) is a β-chemokine that plays a primary role in the inflammatory immune responseby means of its ability to attract and activate leukocytes. CCL5 is secreted by many cell types at inflammatorysites, and it exerts a wide range of activities through the receptors CCR1, CCR3, CCR4, and CCR5. Inflammatoryresponses can be impaired by the sequestration of CCL5 by the cytomegalovirus protein US28. Oligomerizationof CCL5 on glycosaminoglycans is required for CCR1mediated leukocyte adhesion and activation as well asCCL5 ’ s interaction with the chemokine CXCL4/PF4.The deposition of CCL5 on activated vascular endothelialcells is crucial for monocyte adhesion to damaged vasculature, but CCL5 oligomerization is not required for theextravasation of adherent leukocytes.CCL5 is upregulated in breast cancer and promotes tumor progressionthrough the attraction of proinflammatory macrophages in addition to its actions on tumor cells, stromal cells,and the vasculature.