The effect of aging on mucosal host defense
Mucosal immune response is primed at birth and responses generated at this time support specific immunity in later life. Conversely development of mucosal immune response to new antigens is diminished in aging. Availability of key nutrients that are conditionally essential especially in the context of sub-acute infections may limit immune response. A critical hypothesis is that conditionally essential nutrient requirements are associated with aging and form the fundamental basis of observed immune senescence. Since mucosal immunity is modulated by the interaction of microflora with the gut immune system, it is likely that changes in the gut during aging affect this microenvironment. Probiotic lactic acid bacteria offer one approach to stimulating the gastrointestinal immune system thereby enhancing systemic as well as mucosal immune response in aging. The mechanisms of action appear to include specific stimulation of natural killer cells (NK) and the innate immune system.