Therapeutic effects of immature dendritic cells on murine collagen-induced arthritis

Abstract

Objective To explore the therapeutic effects of immature dendritic cells on collagen-induced arthritis (CIA). Methods Murine marrow-derived monocytes were isolated and cultivated with cytokines to generate immature dendritic cells (imDCs) and with lipopolysaccharide (LPS) to generate mature dendritic cells (mDCs). The differentiation and phenotypes were confirmed with flow cytometry. Murine models of rheumatoid arthritis (RA) were established with collagen II transfusion through the caudal vein. On day 6 after first immunization, subdermal injections of imDC, mDC or PBS were administered, and the mice were divided into three groups according to the injection they had received. On day 7 a second immunization was imposed to fortify CIA. Four weeks after the first immunization the severity of CIA was evaluated using an arthritis index (AI), serum levels of IL-10 and TGF-β using ELISA, as well as regulatory T cell (Treg) populations using flow cytometry. Results The expression rates of CD80, CD86 and MHC-II by DCs induced with rrIL-4 and rrGM-CSF were 32.3%, 25.6% and 44.0%, and the rates by DCs induced with rrIL-4, rrGM-CSF and LPS were 91.5%, 90.9% and 94.2%, which identified the differentiation and phenotypes of the imDCs and mDCs. The aveage AI of the imDC group was 7.32±1.63, significantly lower than those of the mDC group (13.64±2.02) and the PBS group (12.78±1.96). The average serum concentrations of IL-10 and TGF-β in the imDC group were significantly higher than in the mDC and PBS groups. The proportion of Treg in the splenocytes of the imDC group was significantly higher than in the mDC and PBS groups. Conclusion CIA was markedly ameliorated by imDC, possibly through up-regulating the expression of anti-inflammatory cytokines like IL-10 and TGF-β and activating the Treg population, which could lead to immune tolerance. Key words: Rheumatoid arthritis; Collagen-induced arthritis; Dendritic cells; Regulatory T cells; Immune tolerance; Cytokines