Mgat2 ablation in the myeloid lineage leads to defective glycoantigen Tcell responses

N-linked glycosylation is a central regulatory factor that influences the immune system in varied and profound ways, including leukocyte homing, T cell receptor signaling and others. Moreover, N-glycan branching has been demon-strated to change as a function of infection and inflamma-tion. Our previous findings suggest that complex-type N-glycans on the class II major histocompatibility com-plex play an important role in antigen selection within antigen presenting cells (APCs) such that highly branched N-glycans promote polysaccharide (glycoantigen, GlyAg) presentation following Toll-like receptor 2 (TLR2)-depend-ent antigen processing. In order to explore the impact of N-glycan branching on the myeloid-derived APC population without the confounding problems of altering the branch-ing of lymphocytes and non-hematopoietic cells, we created a novel myeloid-specific knockout of the β-1,2-N-acetylglu-cosaminyltransferase II (Mgat2) enzyme. Using this novel mouse, we found that the reduction in multi-antennary N-glycans characteristic of Mgat2 ablation had no impact on GlyAg-mediated TLR2 signaling. Likewise, no deficits in antigen uptake or cellular homing to lymph nodes were found. However, we discovered that Mgat2 ablation pre-vented GlyAg presentation and Tcell activation in vitro and in vivo without apparent alterations in protein antigen re-sponse or myeloid-mediated protection from infection. These findings demonstrate that GlyAg presentation can be regulated by the N-glycan branching pattern of APCs, thereby establishing an in vivo model where the T cell-de-pendent activity of GlyAgs can be experimentally distin-guished from GlyAg-mediated stimulation of the innate response through TLR2