Mechanisms of Adaptive Immunity That Prevent Colonization at Mucosal Surfaces

This chapter discusses the chief mechanisms of adaptive immunity in mucosal tissues with particular emphasis on the gut, the best understood of the mucosal immune organs. It describes the organization and main components of the mucosal immune system and the adaptive host defense mechanisms that prevent microbial infection. It also gives schematic representation of the organizational structure of the gut-associated lymphoid tissue (GALT) and the key elements involved in mucosal immunity. It focuses on induction of adaptive immunity at mucosal surfaces, and antibody- and B-cell-mediated immunity in mucosal tissues. Antibodies bound to surface antigens form large immune complexes that prevent colonization and invasion by microbes, facilitating their entrapment in the mucus and subsequent peristaltic or ciliary clearance. The chapter then talks about cell-mediated immunity in mucosal tissues. One of the biggest challenges that lies ahead is the unraveling of the extraordinarily complex mechanisms that underlie the generation of effective immune responses to potentially pathogenic organisms while controlling inflammatory responses to commensal organisms and food antigens. This knowledge will greatly enhance one's ability to prevent inflammatory diseases in organs lined by large mucosal surfaces. Moreover, this information will also be invaluable in designing new generations of vaccines that can be administered via mucosal surfaces, such as attenuated live vectors, which have the potential of inducing strong mucosal and systemic immune responses.