Figure 5.

Impact of IL-21 on B cell proliferation and differentiation in patients with rheumatoid arthritis (RA). (a) Peripheral blood mononuclear cells (PBMC) isolated from RA patients (n = 6) and healthy controls (HC) (n = 6) were labeled with carboxyfluorescein diacetate succinimidyl ester (CFSE) and then stimulated with anti-CD40 (3 μg/ml) and rIL-4 (50 ng/ml) in the presence or absence of rIL-21 (100 ng/ml). After 96 h of culture, B cell proliferation was determined. (b) PBMC isolated from RA patients (n = 14) and HC (n = 8) stimulated with anti-CD40 (3 μg/ml) in the presence or absence of rIL-21 (100 ng/ml). Cells stained with Annexin V were examined after 72 h. (c) PBMC isolated from RA patients (n = 20) and HC (n = 15) were stimulated with a combination of anti-CD40 (3 μg/ml) and anti-IgM (5 μg/ml) in the presence or absence of rIL-21 (100 ng/ml). After 96 h, the frequencies of CD138⁺CD19^low/+ plasmablasts were determined. (d) Secretion of IgG and IgM in culture supernatant was assessed by ELISA *P < 0.05; n.s., not significant. PBS, phosphate-buffered saline.