ABSTRACT
The mucosal immune system is made up of surface and associated lymphoid tissues found in the nasal and oral cavities, gastrointestinal (GI) tract, upper respiratory tract, mammary glands, and urogenital tract. Immunization with a foreign antigen at one mucosal surface was found to generate both local antibodies and also similar antibodies at other mucosal sites, leading to the postulation of a common mucosal immune system (CMIS) (Mayer, 2000). Tissues of the CMIS, including epithelial cells that collaborate with underlying immune tissues, maintain a balance between tolerance and responsiveness at mucosal surfaces which are constantly exposed to microorganisms, foreign antigens, and other potentially harmful substances from food or the environment (Neutra et al., 2001; Neurath et al., 2002). The potential for ingested or inhaled xenobiotics to upset this balance is an area of immunotoxicology that has not been fully explored. This is, in part, because mucosal immunology is still a comparatively young subdiscipline of immunology. In the area of
systemic immunotoxicology, potential immunotoxins are screened using a tiered approach that employs morphological and immune function assays. These assays were selected to account for the complexity of immune responses, as well as the relevance and sensitivity of endpoints in predicting disease (Luster et al., 1992). Successful development of a comparable set of assays for assessing mucosal immunity will depend on advances in our understanding of mucosal immune function and the relationship between mucosal and systemic immune responses.
