BACKGROUND: The aim of this study was to investigate the protective effect of interleukin-6 (IL-6) receptor antagonist tocilizumab (TCZ) on rheumatoid arthritis (RA) and its related mechanism.

MATERIAL AND METHODS: Thirty RA patients receiving long-term methotrexate therapy at moderate and severe active stages were selected and treated with TCZ 8 mg/kg/time iv gtt intravenously guttae every 4 weeks. Peripheral blood was extracted before and 24 weeks after TCZ treatment. Peripheral blood mononuclear cells (PBMC) were collected by density gradient centrifugation. Flow cytometry was used to detect the ratio of CD4 naïve T cells and CD4 memory T cells, Th17 cells, and Treg cells in PBMC. DAS28 score, CRP, RF, and CCP levels in patients were evaluated.

RESULTS: Compared with before treatment, IL-6 receptor antagonist TCZ significantly improved patients’ condition, including DAS28 score, CRP, RF, and CCP levels (P<0.01). Furthermore, TCZ obviously upregulated CD4 naïve T cells proportion and decreased CD4 memory T cells ratio (P<0.01). TCZ also markedly reduced the proportion of Th17 cells and increased the proportion of Treg cells (P<0.01).

CONCLUSIONS: TCZ can treat RA patients through regulating the ratio of CD4 naïve T cells, CD4 memory T cells, Th17 cells, and Treg cells in PBMC.

Keywords: Antibodies, Monoclonal, Humanized - therapeutic use, Antirheumatic Agents - therapeutic use, Arthritis, Rheumatoid - prevention & control, CD4-Positive T-Lymphocytes, Interleukin-6 - metabolism, Leukocytes, Mononuclear - drug effects, Receptors, Interleukin-6 - antagonists & inhibitors, Severity of Illness Index