Recent progress in senescence-associated gut mucosal immunity

The immune response in gut-associated lymphoid tissues (GALT) is altered in the aging process. Senescence-induced quantitative decline and qualitative changes of GALT T and B cells and their subpopulations contribute largely to the impaired gut mucosal immune responses. Thus, not only direct cell-to-cell contact interactions, but also patterns of immuno-regulatory cytokine production and serum-soluble cytokine, such as interleukin-2 receptors are also altered, causing both cellular and humoral immune abnormalities in GALT. One of the characteristic features includes functional defects of suppressor T cells. As a consequence, relative hyperfunction of helper T cells ensures. The defective immune response of both function and control of aged GALT may help to explain the increased incidence of infection and neoplasia in the gastrointestinal tract with age. On the subcellular level, these aged T and B cells impair transmembranous signal transduction. Trials of immune interventions to reduce or reverse immunosenescence in GALT were made in animals. The results of adoptive transfer of in vitro educated helper T cells from aged GALT are encouraging. Further innovative immunologic interventions are indicated.