CCL2/JE/MCP-1, is a chemokine that binds the receptor CCR2 and induces the chemoattraction of mononuclear cells. It induces the activation of monocytes, NK cells, lymphocytes, and basophils. Additionally, CCL2 promotes Th2 polarization in CD4+ T cells, and CCL2-mediated recruitment of monocytes to sites of inflammation contributes to disease severity in atherosclerosis, multiple sclerosis, and allergic asthma. Endogenous proteolytic trimming of CCL2 at the N-terminus, including the N-terminal pyrrolidone carboxylic acid-modified glutamine, downregulates activity but not receptor binding.