The Mucosal Immune System: The Close Relationship of Microbiota and Aging

It has been shown that the intestinal microbiota changes with aging. Accompanying this age-associated alteration, low levels of chronic inflammation and reduced levels of pathogen-specific immunity, known as inflammaging, are observed. A lack of oral tolerance has also been noted during the early stage of aging which may cause inflammaging and the subsequent induction of low levels of gastrointestinal immune responses. Since the alteration of intestinal microbiota and diminished immunity are closely associated in the elderly, it may be necessary to rejuvenate aged intestinal microbiota and maintain it in order to prevent respiratory infection, which exhibits high mortality in the elderly, although it could be a difficult task at present. Since the upper respiratory immune system is less influenced by aging and intestinal microbiota changes, newly developed innovative nasal vaccine approaches may overcome reduced levels of mucosal and systemic immunity. Such strategies may lead to the extension of healthy life expectancy which would also contribute to the establishment of a society with sustainable development goals.