Cutting edge:: Human Th17 cells are identified as bearing CCR2+CCR5- phenotype

Recent reports have shown that IL-17-producing CD4(+) T cells (Th17 cells) belong to a distinct helper T cell lineage and are critically involved in the pathogenesis of autoim- mune diseases and allergies. However, the chemokine receptor profile of Th17 cells remains to be clarified In this study, we report that human Th17 cells are identified as CCR2(+) CCR5(-) memory CD4(+) T cells. Analysis of PBMC from healthy donors showed that CCR2(+) cellsproduce much larger amounts of IL-17 than CCR2(-) cells, indicating the preferential expression of CCR2 on Th17 cells. Notably, CCR2+ CCR5- memory CD4+ T cells produced a large amount of IL-17 and little IFN-gamma, whereas CCR2(+) CCR5(+) cells reciprocally produced an enormous amount of IFN-gamma but little IL-17. Moreover, a higher expression of T-bet was seen in the CCR5+ memory T cells. These results indicate that absence of CCR5 distinguishes human Th17 cells from Th1 cells.