Abstract: Objective: To investigate the effect of myeloid-derived suppressor cells (MDSC) on pro-liferation of B lymphocytes in rheumatoid arthritis (RA) patients. Methods: The peripheral blood specimens were collected from 15 healthy adults and 38 RA patients who were divided into high disease activity group, medium activity group and low activity group according to their 28-joint disease activity score (DAS28). And the frequencies of MDSC were determined by flow cytometry. Then, B cells and MDSC were isolated by flow cytometry, respectively. B cells were labeled with carboxyfluorescein diacetate succinimidyl ester (CFSE) and then were co-cultured with MDSC in the presence of 3 mg/L anti-CD40 antibody and 10 mg/L CpG, for 3 days. Flow cytometry was performed to investigate the proliferation of B cells. Results: MDSC expanded markedly in high disease activity patients (7.13%±2.17%) compared with medium (5.35%±1.36%) and low disease activity patients (4.72%±1.08%) or healthy controls (4.79%±1.02%) (P<0.05), and there were no statistical differences between healthy controls, medium and low disease activity RA (P>0.05). Moreover, the frequencies of MDSC were positively correlated with the DAS28 (P<0.05). After co-culture, MDSC significantly promoted B cell proliferation (P<0.01). Conclusion: Our studies showed that MDSC expanded obviously in high disease activity RA patients, and their frequencies were positively correlated with the disease activities. Furthermore, MDSC could promote autologous B cell proliferation remarkably in vitro. These findings suggest that MDSC might be involved in RA pathogenesis through regulating B cell functions.

Key words: Myeloid-derived suppressor cells, Arthritis, rheumatoid, B-lymphocytes, Cell proliferation