Surveillance B lymphocytes and mucosal immunoregulation.

Abstract

Mucosal lymphocyte homeostasis involves the dynamic interaction of enteric microbiota, the intestinal host epithelium, and the mucosal immune system. Dysregulation of mucosal lymphocyte homeostasis results in a variety of intestinal disorders, notably inflammatory bowel diseases like ulcerative colitis and Crohn's disease. One key cellular component regulating homeostasis are B lymphocytes that reside in gut-associated lymphoid tissue. This compartment includes Peyer's patches, isolated lymphoid follicles, lamina propria, and mesenteric lymph nodes. Recent data have pointed to two new and exciting aspects of B cells in the gut. First, there has been progress on identification and functional analysis of abundant isolated lymphoid follicle B cells that are key mediators of IgA genesis. Second, several groups have now clarified the functional identification and characterization of immunoregulatory B cells in the gut. This review examines the novel aspects of these B cells, and examines how each plays a role in mediating mucosal homeostasis in this bacteria-laden compartment.