IgA plasma cell development

Abstract

Evolution in biological systems is rarely wasteful; it involves both adaptation and conservation of resources. In this context especially, the quantity of IgA secreted onto mucosal surfaces and the cellular processes that generate it are all the more remarkable. Approximately 1010 plasma cells per meter of gut are situated in the diffuse connective tissue stroma between the epithelium and the muscularis mucosa referred to as the lamina propria (Fig. 2.1) (Brandtzaeg et al., 1999; Brandtzaeg and Pabst, 2004). These produce antibody, most of which is immumoglobin A (IgA), so that ∼3-5g of IgA is actively transported each day into the lumen of the human gut (Conley and Delacroix, 1987). This secreted antibody has a critical role in maintaining homeostasis in an environment where the immune system and potentially proinflammatory bacterial stimuli are closely juxtaposed and separated by a single epithelial layer (Fagarasan et al., 2002). The aim of this chapter is to discuss the mechanisms that generate, diversify, and disseminate this extensive IgA-producing plasma cell population. There are considerable interspecies differences in mucosal lymphoid tissue that will be identified where relevant, but the final outcome in all species is the same: the production of the largest population of plasma cells in the body.