Role of the Innate Immune System and Host-Commensal Mutualism -- Molecular Networks Orchestrating GALT Development -- Lymphoid Tissue Inducer Cells in Intestinal Immunity -- Specificity and Plasticity of Memory LymphocyteMigration -- IgA Adaptation to the Presence of Commensal Bacteria in the Intestine -- Intestinal IgA Synthesis: A Primitive Form of Adaptive Immunity That Regulates Microbial Communities in the Gut -- B Cell Recruitment and Selection in Mouse GALT Germinal Centers -- Structural Insights into Antibody-Mediated Mucosal Immunity.