This resource provides information about mucosal barrier function, innate humoral factors, TLR ligands and their receptors, commensal bacteria regulate mucosal gene expression, innate humoral factors: Defensins, luminal factors, enrichment of dimeric (d)IgA in mucosal secretions relative to serum which contains monomeric IgA, structure of polymeric Ig receptor (pIgR), intracellular transport of pIgA via pIgR, quantification of IgA production in mucosal secretions, intrinsic barrier function of epithelium, pathways for antigen-uptake from the lumen, epithelial transport of macromolecules, antigen presentation by absorptive epithelial cell, Peyer?s patch development, and concept of the common MALT.