Compared with classical Fc N-glycosylation, Fab N-glycosylation displays site heterogeneity and structural diversity. It contributes to immune regulation by modulating antibody stability, half-life, and antigen-binding activity, as well as by mediating blocking antibody effects. This review highlights the expression patterns and potential mechanisms of Fab N-glycosylated IgG in autoimmune diseases, pregnancy-induced immune tolerance, and tumor immune evasion, and discusses its structural and functional similarities to IgG4. Although Fab N-glycosylation plays an important role in both physiological and pathological conditions, the complexity of its glycan structures and variability in glycosylation sites hinder a precise understanding of its functional impacts. Clarifying these aspects is expected to emerge as a major focus in glycomics and antibody engineering research.

Background: Pneumonia is a leading global cause of morbidity and mortality, and individual differences in susceptibility and prognosis cannot be fully explained by traditional risk factors.Methods:This large-scale prospective cohort study based on UK Biobank (373,648 participants) aimed to explore the association between allostatic load (AL) and incident pneumonia, as well as post-pneumonia 30-day severe outcomes, and to investigate the regulatory effects of healthy lifestyle and genetic susceptibility.Findings: The results showed that elevated AL was significantly associated with an increased risk of overall pneumonia (HR=1·30, 95%CI: 1·26–1·35) in a dose–response manner, and this association was consistent across viral, bacterial and unspecified subtypes. Among AL subsystems, immune and renal dysfunction contributed the most to pneumonia risk. High AL was independently linked to elevated 30-day severe complications and acute myocardial infarction risk after pneumonia. The adverse effect of AL was not modified by polygenic risk, while a favorable healthy lifestyle could attenuate AL-related pneumonia risk by approximately 31·8%, with a significant additive interaction between high AL and unhealthy lifestyle.InterpretationIn: conclusion, AL is an independent risk factor for pneumonia incidence and poor short-term prognosis, and lifestyle intervention can mitigate this risk, providing a new strategy for pneumonia risk stratification and prevention.