Abstract
Th17 and TfH cells are thought to promote tissue inflammation and autoantibody production, respectively, in autoimmune diseases including rheumatoid arthritis (RA). TfH cells that co-express Th17 markers (CXCR5+Th17) encompass both of these pathogenic functions, and are increased in some human autoimmune settings including juvenile dermatomyositis. We investigated CXCR5+Th17 cells in RA subjects with stable or active disease and before and after TNF inhibitor therapy. CXCR5+Th17 cell frequency was increased in RA compared to healthy controls, but other helper T cell subsets were not different. CXCR5+Th17 cells correlated with disease activity in subjects with active RA prior to initiation of TNF inhibitor therapy. Baseline CXCR5+Th17 cells also correlated with numbers of swollen joints as late as one year post-therapy. CXCR5+Th17 cell frequencies were unaltered by TNF blockade and in fact remained remarkably stable within individuals. We conclude that CXCR5+Th17 cells are not a direct target of TNF blockade and therefore cannot serve as a biomarker of current disease activity. However, basal CXCR5+Th17 cell frequency may indicate underlying differences in disease phenotype between patients and predict ultimate success of TNF inhibitor therapy.