Methotrexate, combined with cyclophosphamide attenuates murine collagen induced arthritis by modulating the expression level of Breg and DCs

To explore the mechanism of methotrexate (MTX) and its combination with cyclophosphamide (CTX) in collagen-induced arthritis (CIA), we investigated the levels of several immune cells and cytokines in mice with different treatments. CIA was induced in DBA/1 mice at the age of 7 weeks by primary immunization with 100 μl emulsion containing 2 mg/ml bovine type II collagen which was mixed with complete Freund's adjuvant (CFA). The booster immunization was performed with 50-100 μl emulsion containing 2 mg/ml bovine type II collagen (CII) mixed with incomplete Freund's adjuvant (IFA). MTX, CTX or both were administrated after the booster immunization. Therapeutic effect was evaluated by arthritic scores, X-rays and assessment of histopathological joint destruction. The expression of TNF-α, IL-6, IL-23, IL-10 were also measured. The frequencies of different immune cell subsets in the lymph node, spleen and bone marrow were determined by flow cytometry analysis. Our results showed that CTX and MTX treatment attenuated the severity of arthritis of CIA mice and reduced the levels of several cytokines. CTX and MTX treated mice showed a lower frequency of B cells in bone marrow. Also, when treated the CIA mice with MTX, alone or together with CTX, the lymph nodes and spleen exhibited a decrease in regulatory B cells (Breg) and dendritic cells (DCs). Notably, the combination of MTX and CTX had a more pronounced effect. By measuring the levels of different immune cells those participated in the development of rheumatoid arthritis (RA), our experiment may help to evaluate the therapeutic effects and prognosis of arthritic diseases.