CCL8, also known as MCP-2, is a beta chemokine initially isolated from human MG-63 osteosarcoma cells stimulated with IL-1beta. CCL8 (MCP-2) has structural and functional similarity with MCP-1 and MCP-3, and it is often co-induced with those chemokines in mononuclear cells. IFNgamma is a strong inducer of CCL8 in monocytes and fibroblasts. CCL8 can be processed and secreted as a truncated chemokine CCL8 (6-75). This isoform does not chemoattract monocytes, but it binds to the CCR2 receptor and induces its internalization; as a result, CCL8 inhibits MCP-1 (CCL2) and MCP-2 (CCL8) ERK signaling and antagonizes the chemotactic activity of several CCR2 ligands (MCP-1/CCL2, MCP-2/CCL8, MCP-3/CCL7). CCL8 is highly expressed in the skin, and it serves as an agonist for the chemokine receptor CCR8, but not for CCR2. Therefore, it has been speculated that the CCL8-CCR8 interaction is a crucial regulator of Th2 cell homing, which drives IL-5-mediated chronic allergic inflammation. In addition, CCL8 binds CCR5 receptor with high affinity and inhibits the replication of human immunodeficiency virus type 1. CCL8 is highly expressed in different human diseases, and it is a potential biomarker for the diagnosis of graft-versus-host diseases and tuberculosis.