CCR2, the receptor for CCL2, is expressed on human effector memory CD4+ T cells that are useful for rapid recall responses [31], on Th17 cells recruited to the lung during allergic reactions [32], on γ,δ T-cells infiltrating tumors [30], and on CD4+ T cells where they can have negative influence in Crohn’s disease [33]. Here, CCR2 is linked to Crohn disease.