N-glycan branching regulates B cell peripheral functions

Abstract

Abstract N-glycosylation is important for regulating many immune cell functions. To date, the role of N-glycan branching on influencing B cell antigen presenting cell (APC) function is not known. Proper CD4+ TH cell activation requires APC peptide presentation together with CD80/CD86 co-stimulation. CD80 and CD86 respectively promote TH1 cell-mediated and TH2 humoral immune responses. APCs then release cytokines that further dictate TH cell polarization into TH1, TH2, TH17 or TREG cells. In vitro stimulated N-glycan branching deficient B cells have higher CD80 and lower CD86 surface levels, and produce more pro-inflammatory TNFα and less anti-inflammatory IL-10. Furthermore, N-glycan branching deficient B cells have increased toll-like receptor 4 (TLR4) surface levels resulting from lack of endocytosis. Sustained surface TLR4 enhanced intracellular signaling towards NFκB activation as measured by increased phosphorylation of TAK1 and p38. Endosomal TLR4 signaling, which can lead to IRF3 activation, was diminished as seen by decreased expression of TRAF3 and phosphorylation of TBK1. Our results show N-glycan branching on peripheral B cells restricts NFκB activation to limit pro-inflammatory cytokine expression and CD80 surface levels, ultimately dampening TH1 cell-mediated responses. This study demonstrates N-glycosylation is important for regulating B cell APC function.