We showed that rIL-21 upregulated the frequencies of plasmablasts (CD138+CD19low/+) both in RA patients (7.30% ± 1.01% vs. 9.24% ± 1.08%, P < 0.05; Figure 5c) and HC (3.26% ± 0.66% vs. 4.12% ± 0.93%, P < 0.05; Figure 5c). The gene discussed is SDC1; the disease is rheumatoid arthritis.