Abstracts

#33 Semaphorin 3E reduces the activation of splenic CD11c+ cells and T cell priming in active colitis

Laëtitia Kermarrec, University of Manitoba; Nour Eissa, University of Manitoba; Omar Elgazzar, University of Manitoba; Charles N Bernstein, University of Manitoba; Jean-Eric Ghia, University of Manitoba

Introduction

Inflammatory bowel diseases (IBD) involve an increase of dendritic cells (DC) infiltration and cytokines production. Semaphorins have​ emerged as an essential axis in DC immune responses. Previously, we demonstrated that Sema3E regulates colitis via the modulation of DC-IL-12p40 release. This study aims to determine the role of Sema3E on colitis and on DC regulation and T-cell priming.

Methods

mRNA expression level of Sema3E in active UC patients using RT-qPCR, and its correlation analysis with pro- and anti-inflammatory markers were determined. Colitis was induced by dextran sulfate sodium (DSS 5%) for 5 days in Sema3E-/- and Sema3E+/+ mice treated or not with recombinant-Sema3E-Fc. Disease severity, colonic, Sema3E, INF-γ, TNF-α, IL-4, IL-17, IL-23, IL-12p70 and IL-12p40 were quantified. IL-12p70, p40 and IL-23 levels in isolated splenic DCs were determined in presence of Nk-B-inhibitor (BAY-11-7082) or activator (betulinic-acid). IFN-γ, IL-17 levels from DC/CD4+CD25-T cell co-culture were determined in the presence of anti-p19-mAb or p35-mAb.

Results

In active UC biopsies, Sema3E mRNA was significantly decreased and negatively and positively correlated with pro-and anti-inflammatory cytokines respectively. In colitic Sema3E+/+ mice, Sema3E level was significantly decreased. In colitic Sema3E-/- mice, clinical score, IL-17, IL-12p40, p70, IL-23, IFN-γ were significantly increased compared to Sema3E+/+ with no effect on IL-4. Colitic SemaE-/- splenic CD11c+ cells showed an increased production of IL-12p70, p40 and IL-23, with no effect on CD11c+ proliferation; Sema3E-Fc decreased the cytokines production as much as BAY 11-7082 whereas betulinic acid abrogated Sema3E-Fc effect. Colitic SemaE-/- splenic CD11c+ cells showed higher effective T-cell priming reflected by an increase of IFN-γ and IL-17 release by CD4+CD25- T cells. Addition of the anti p19-mAb in the medium abolished the production of IL-17 in DCs/CD4+CD25- T cells co-cultures; and anti p35-mAb the IFN- production.

Conclusion

Sema3E reduces colitis and may lead to improved therapeutic strategies in IBD.