Figure 4b showed that IL-21R expression on B cells was significantly enhanced in response to rIL-21 in RA patients (29.11% ± 4.11% vs.38.13% ± 4.72%, P < 0.05; Figure 4b) but not in HC (19.84% ± 2.68% vs. 21.71% ± 2.95%, P > 0.05). The gene discussed is IL21R; the disease is rheumatoid arthritis.