Mucosal immune system: implications in otitis media with effusion.

The ontogeny of the mucosal immune system as it relates to the development of lymphoid tissue in the respiratory tract and the gastrointestinal tract has been studied quite extensively over the past few years. It is apparent now that the bronchus-associated lymphoid tissue and gut-associated lymphoid tissue are the major sources of immunocompetent precursor B lymphocytes. After the induction of antigens in the respiratory tract or the gastrointestinal tract, precursor lymphoid cells in these sites are preferentially activated to undergo significant proliferation. Such antigen-sensitized cells eventually migrate to other mucosa sites, such as mammary glands, genital tract, conjuctiva, etc. Recent evidence has suggested that the immunocompetent tissue observed in the middle ear cleft during otitis media with effusion may function as an extension of the mucosal immune system in the upper respiratory tract. The implications of these observations relative to middle ear disease are discussed.