PDCD1 and rheumatoid arthritis: We observed an enhancement in the secretion of pro-inflammatory cytokines (IFN-γ, TNF-α, IL-6, IL-17A, IL-21, and CXCL13), the cytotoxic molecules (Perforin and Granzyme B) (Fig. 3B) and the expression of relative transcription factors (T-bet, Eomes, BATF, and Blimp1) (Fig. S5) by RA CD4+PD-1+T cells.