Regulatory T Cell Networks in the Secretory Immune System
The mucosal surfaces of man and other mammals are in direct continuity with the external environment. As such, they are continually exposed to antigens from the environment and represent the major bodily site of antigenic exposure and recognition. In the case of ingested antigens, there is selective uptake into the Peyer’s patches (PP), which are distinct aggregates of lymphoreticular nodules along the anti-mesenteric aspect of the gastrointestinal (GI) tract and a major component of the gut-associated lymphoreticular tissues (GALT). The PP contain a large subpopulation of B lymphocytes that are committed to IgA synthesis (1), macrophages (2), dendritic accessory cells (3) and regulatory T lymphocytes of the T-helper (Th), T suppressor (Ts) and T contrasuppressor (Tes) subsets (4–7). Overlying the PP is a lymphoepithelium which contains microfold cells (M cells; also termed follicular-associated epithelial cells) with highly developed pinocytotic channels which allow sampling of antigens from the gut lumenal contents, and transport of these antigens to the underlying lymphoreticular cells (8,9). The oral administration of antigen leads to the stimulation of both the B lymphocyte (follicular) and T lymphocyte (parafollicular) zones within the PP, but B lymphocyte maturation to the plasma cell stage does not occur in this tissue.
KeywordsOral Tolerance Cell Mediate Suppression Microfold Cell Secretory Immune System Plasma Cell Stage
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