Exploratory analysis of early changes in peripheral immune cell proportions and clinical response following methotrexate and biologic treatment in rheumatoid arthritis.

Objective: To examine the relationships between changes in the proportions of immune cell populations and clinical response at 2 weeks post-treatment with methotrexate (MTX), tumour necrosis factor (TNF) inhibitors, or abatacept, with treatment efficacy at week 12 in patients with rheumatoid arthritis (RA). Methods: Peripheral blood samples were collected from 30 patients with RA who received MTX (n=10), a TNF inhibitor+MTX (n=10), and abatacept+MTX (n=10) in this observational study. Of these, 25 patients completed the 12-week follow-up and were included in the efficacy and correlation analyses (MTX n=9; TNF inhibitor+MTX n=8; abatacept+MTX n=8). Immune cell phenotypes were determined using 11-colour flow cytometry at baseline and 2 weeks after drug administration. Results: Baseline proportions and changes in several immune cell types at 2 weeks post treatment correlated with the efficacy of arthritis treatment at week 12. Specifically, a higher baseline proportion and a greater decrease at week 2 in class-switched memory B cells following MTX administration were significantly associated with treatment efficacy for arthritis, as were the same changes in activated Th1 cells following abatacept administration. Increases in effector memory CD8+ T cells were also significantly correlated with the efficacy of TNF inhibitor treatment in RA patients. Conclusion: This exploratory study identified a potential association between baseline or early changes in immune cell populations and subsequent clinical responses in RA.