Objectives: Abatacept (ABA), a molecule used in the treatment of rheumatoid arthritis (RA), competes with the engagement of CD28, a T-cell receptor for co-stimulatory signals. CD28-mediated signalling regulates several T-cell functions, including inflammatory cytokine production and regulatory T cells (Treg) differentiation. Therefore, our objective was to evaluate the effects of ABA on peripheral blood T-lymphocyte cytokine production and on the number of circulating Treg.
Methods: In 24 RA patients treated with ABA for at least 6 months the proportions and absolute numbers of peripheral blood T cells producing interferon-gamma (IFN-γ) and interleukin-17 (IL-17) after in vitro stimulation, as well as those of Treg were longitudinally evaluated by flow cytometry.
Results: At baseline, compared with 16 healthy controls, RA patients had a higher percentage of CD4+ and CD8+ T cells producing IL-17 (p=0.021, and p=0.006, respectively), as well as of circulating Treg (p=0.041). After 6 months of therapy with ABA, there was a decrease of the percentage of IFN-γ- and IL-17-producing CD8+ T cells (p=0.033 and p=0.035, respectively), and of Treg (p=0.008), while that of IL-17-producing CD4+ T cells decreased after 12 months of treatment (p=0.005). The number of IL-17-producing T cells and of Treg, higher than in controls at baseline, normalised after ABA therapy. All these variations were statistically significant only in RA patients with EULAR good clinical response (n=17).
Conclusions: The blockade of CD28 signal caused by ABA induces the decrease in peripheral blood of IL-17- and IFN-γ-producing T cells.