CCL2, also called monocyte chemotactic protein1 (MCP1) or JE, is a member of the CC or beta chemokine family that is best known as a chemotactic agent for mononuclear cells . Human CCL2 cDNA encodes a 99 amino acid (aa) precursor protein with a 23 aa signal peptide and a 76 aa mature protein . Removal of the first 5 aa of the mature protein, including the N-terminal pyrrolidone carboxylic acidmodified glutamine, occurs naturally by metalloproteinase cleavage and downregulates activity but not receptor binding. CCL2 may form multiple bands from 8.713.5 kDa on SDSPAGE due to noncovalent dimerization and variable carbohydrate content. Mature human CCL2 shares 7879% aa identity with canine, porcine and equine CCL2, while mouse and rat express a form of CCL2 that is extended by 49 aa and shares only 56% aa identity within the common region. Human CCL2 can, however, induce a response in murine cells.