Impaired T cell immunity in the elderly via N-glycosylation

Abstract

Aging is associated with a decline in immune function, increasing the frequency and severity of infection in the elderly. We have previously shown that Asparagine (N) – linked protein glycosylation is a critical negative regulator of T cell immunity in both mice and humans. Here we report N-glycan branching in T cells increases with age, leading to T cell hypo-activity and increased susceptibility to infection. Reducing N-glycan branching rejuvenates T cell activation, proliferation and pro-inflammatory TH17 over anti-inflammatory Treg differentiation in aged T cells. Susceptibility of aged mice to Salmonellae typhimurium invasion/dissemination was reduced by lowering N-glycan branching. A critical metabolic precursor of N-glycosylation and branching is N-acetylglucosamine (GlcNAc), a common amino sugar that is part of the regular human diet. GlcNAc is endogenous to human serum, increases with age and correlates with N-glycan branching in T cells. T cell specific deletion of N-acetylglucosamine kinase, thereby blocking salvage of GlcNAc into N-glycans, reduces branching in aged T cells and rejuvenates T cell activation. Collectively, our results suggest that age-dependent increases in N-glycan branching, via increased supply of GlcNAc, impairs T cell immunity in the elderly. Therapeutic inhibition of N-glycan branching may provide a novel mechanism to rejuvenate T cell responses and reduce infection risk in the elderly.