What role does IgG play in longevity?

The role of IgG (immunoglobulin G) in longevity is indirect and not supported by strong evidence. IgG is the most abundant antibody in blood and crucial for adaptive immunity, especially against recurring pathogens and immune surveillance. With aging, the IgG repertoire undergoes changes: diversity declines while autoreactive and proinflammatory IgG subtypes (e.g., IgG1, IgG3) may increase. This has been linked to chronic inflammation and age-related diseases. Some observational studies suggest that low total IgG levels correlate with higher infection risk in older adults, potentially impacting lifespan. However, the evidence is predominantly mechanistic and observational; no randomized trials directly demonstrate a causal role of IgG in longevity. IgG levels vary widely due to genetics, infections, vaccinations, and lifestyle. Measuring IgG in blood can serve as a biomarker of immune aging (immunosenescence) but is not a standalone predictor of longevity. In summary, IgG is an important immune component, but its specific contribution to longevity remains complex and inconclusive.