Studies indicated that CXCR5+ Tfh cells were present in the B-cell area of lymphoid tissue from early RA patients, and both CXCR5+ and CXCR5+PD-1+ cTfh cell proportions were higher in untreated early RA patients than in healthy controls (HC) (54–56). Here, PDCD1 is linked to rheumatoid arthritis.