Studies using CXCR5+PD-1+ or CXCR5+ICOS+ to mark Tfh cells indicated an active Tfh differentiation in RA (15, 16, 18) while those applying CCR6 and CCR3 to stratify Tfh cells demonstrated a biased Tfh polarization into CXCR5+CCR6+CXCR3− (Th17-type Tfh) and/or CXCR5+CCR6−CXCR3− (Th2-type Tfh) subsets in RA patients (18, 19). This evidence concerns the gene ICOS and rheumatoid arthritis.