CCR2 identifies two subtypes of pathogenic human type 17 Th cells and has a non-redundant role in their transendothelial migration

Abstract

Abstract We have shown previously that CCR2 is expressed on highly differentiated human Th memory cells as well as mucosal associated invariant T (MAIT) cells. CCR2+ T cells typically co-express a combination of other inflammation-associated chemokine receptors, including CCR6, which is found on all type 17 T cells. We found that the CCR6+ CCR2+ human Th cell population is enriched in cells with a pathogenic cytokine and cytotoxic profile. Single-cell analysis revealed two subtypes of such CCR6+ CCR2+ cells, either biased to produce GM-CSF or IFNg. Pathogenic activity requires migration into inflamed tissue, and to understand the roles for CCR2, CCR6 and other chemokine receptors expressed on these cells in extravasation we used flow chambers containing HUVEC activated with TNFa and/or IFNg. We found that although CCR6, CCR5 and CXCR3 (but not CCR2) were capable of mediating T cell arrest, only CCR2 was active in transendothelial migration. CCR2’s activity was a function of the localization of its principal ligand, CCL2, in endothelial cells. Native CCL2 was found intracellularly but not on the cell surface. Immediate pre-treatment of cells with CCL2 or using HUVEC transduced to express a CCL2-CXCL9 chimeric chemokine that bound to surface glycosaminoglycans enabled CCR2 to mediate T cell arrest. These studies reveal the integration of transendothelial trafficking and a pathogenic effector profile in type 17 human Th cells and demonstrate redundant and non-redundant roles for the multiple chemokine receptors on these cells due to chemokine positioning. Our findings could inform more effective combinatorial inhibition or expression of chemokine receptors/ligands to regulate the migration of highly inflammatory T cells. Supported by NIH