CD4 and acquired polycythemia vera: When evaluating CD4+ T-cell subsets by observing expression of CXCR3 and CCR6, ICOS+PD-1+ circulating Tfh (cTfh) 2 cells, the Th2 phenotype of cTfh cells, were found to be associated with the production of autoantibodies against DSG3 in patients with PV (24).