Types Of Mucosal Immunity Of Mammals Synthesis And...

Discussion One of the cardinal features of mucosal immunity in mammals is the synthesis and transepithelial transport of large amounts of SIgA that contribute to maintaining homeostasis with the enteric microbiota (Macpherson et al., 2008; Mestecky, 1987). Endogenous SIgA production normally begins shortly after weaning, coincident with a shift from breast milk to solid food as the main nutrition source and accelerated colonization of the intestine by commensal bacteria. The initial endogenous SIgA response is dominated by IgA antibodies with few if any mutations in their variable regions and low avidity for the bacteria in the lumen (Lindner et al., 2012). As the mucosal immune system matures, most of the SIgA antibodies secreted in the intestine carry mutations concentrated in the complementarity-determining regions of VH and VL domains. These mutations occur as a result of T-cell dependent somatic mutation in GCs and lead to increased avidity of the antibodies for target antigens. B cell c lones responding to foreign antigens that persist can undergo additional rounds of somatic mutation in GALT GCs contributing to further increases in antibody affinity (Bergqvist et al., 2013). A major source of antigens driving SIgA production in the intestine is the commensal enteric flora. As a result, germ-free mice have a markedly attenuated SIgA response (Benveniste et al., 1971; Hapfelmeier et al., 2010). Furthermore, SIgA production in germ-free mice can be restored to near