Regulation of immunologic homeostasis in peripheral tissues by dendritic cells: The respiratory tract as a paradigm

Dendritic cells are now recognized as the gatekeepers of the immune respons e, possessing a unique potential for acquisition of antigens at extremely l ow exposure levels and for efficient presentation of these in an immunogeni c form to the naive T-cell system. Dendritic cell populations throughout th e body exhibit a wide range of features in common that are associated with their primary functions, and these are considered in the initial section of this review. In addition, it is becoming evident that the properties and f unctions of these cells are refined by microenvironmental factors unique to their tissues of residence, a prime ex-ample being mucosal microenvironmen ts such as those in respiratory tract tissues, and the latter represents th e Focus of the second section of this review.