Comparative analysis of the effects of anti-IL-6 receptor mAb and anti-TNF mAb treatment on CD4+ T-cell responses in murine colitis

Abstract

The efficacy of anti-tumor necrosis factor monoclonal antibody (anti-TNF mAb) for Crohn's disease (CD) is well established, and anti-interleukin-6 receptor (anti-IL-6R) mAb has also been reported to be effective in CD. It is, however, unclear if the efficacy and mechanisms of both agents are different in CD therapy. Using an adoptive transfer colitis model, we compared the efficacy of anti-IL-6R mAb, anti-TNF mAb, and TNF receptor-Fc fusion protein (TNFR-Fc), and their modes of action on CD4+ T cells. We also investigated the role of Th1 and Th17 cells in colitis using the same model. The histological scores for the anti-IL-6R mAb and anti-TNF mAb groups but not for TNFR-Fc group were much lower than that for the control group, and the score was the lowest for the anti-IL-6R mAb group. The frequency of proliferating CD4+ T cells was reduced in anti-IL-6R mAb and anti-TNF mAb groups, but not in the TNFR-Fc group, whereas the frequency of apoptotic CD4+ T cells was similar in all groups. Anti-IL-6R mAb suppressed the induction of Th17 cells and increased the frequency of lamina propria regulatory T cells, whereas anti-TNF mAb exerted no influence on CD4+ T-cell differentiation. A deficiency in interferon-γ and/or IL-17 in CD4+ T cells reduced the severity of colitis. Our findings suggest that suppression of the proliferation of pathogenic CD4+ T cells is the major mode of action of biological agents for colitis therapy. Anti-IL-6R mAb might have benefits in CD patients with Th17 dominance and impaired Treg frequency.