Antigen Presentation An Overview

Marcel Dekker Inc. 270Madison Avoiue, New Yori New Yoric 10016 

Within the respiratory tract, several cell types are capable (based on then-expression of surface class II MHC) of antigen presentation. These may be broadly categorized as either professional APC, which may include B cells, macrophages, and DC, or opportunistic APC, such as fibroblasts and epithelial cells, either eiliated or type II pneumonocytes. The potential for each of these populations to contribute to T-cell activation is dependent on factors such as the host s existing immune status, degree of local inflammation, and physicochemical properties of the inhaled particle or antigen. 

By their very nature, larger, insoluble particulate material may be restrieted in their access to cell populations located below the epithelial cell surface therefore, the partieipation of active phagocytic cells at the airway luminal surfaee may be mandatory. In contrast, soluble materials are readily transloeated to intraepithelial or submueosal mieroenvironments by pinocytotic or reeeptor-mediated pathways, and thereby gain aeeess to DC populations. The mechanisms by which environmental antigens may breach the epithelial barrier have been extensively reviewed elsewhere (5,6). 

---