Antigen Binding to Secretory Immunoglobulin A Results in Decreased Sensitivity to Intestinal Proteases and Increased Binding to Cellular Fc Receptors

The Role of Secretory Immunoglobulin A in the Natural Sensing of Commensal Bacteria by Mouse Peyer's Patch Dendritic Cells

“…Source of SIgA-Culture supernatants of mouse hybridoma cell clone IgAC5, specific for Shigella flexneri serotype 5a LPS, grown at 37°C in RPMI 1640 medium complemented with 10% fetal calf serum (FCS) were used as a source of IgA (24); to reconstitute SIgA, equimolar purified polymeric IgAC5 mAb and recombinant mouse SC were combined as described (26).…”

“…Various cell types in PPs were detected upon incubation in PBS-5% FCS with biotinylated anti-CD11c mAb (1/10; BD Biosciences), purified anti-CD4 rat IgG (1/50; BD Biosciences), or purified anti-CD45R rat IgG (1/50; Invitrogen), followed by Cy3-or Cy5-labeled streptavidin (1/500; both from Amersham Biosciences) or anti-rat IgG conjugated to Alexa Fluor 647 (1/100; Invitrogen). Endogenous SIgA was detected with rabbit anti-mouse SC antiserum at 1/200 dilution (26) and goat anti-rabbit IgG coupled to Alexa Fluor 647 (1/200; Invitrogen). M cells were stained with rhodamine-coupled UEA-1 (Vector Laboratories, Burlingame, CA) used at a concentration of 20 g/ml.…”

Role of secretory IgA in the mucosal sensing of commensal bacteria

“…While the above-reported experiments support an intrinsic effect of the association of bacteria with non-specific SIgA via interactions with carbohydrate moieties, 49 we cannot exclude that antigenspecific recognition may be of an added value for the sensing process. In this respect, association between an antigen and its cognate specific SIgA triggers structural changes in the antibody, which in turn confers enhanced interaction with cognate receptors, 50 a feature which may explain the favored interaction of SIgA-coated commensals to M cells or DCs. Moreover, experiments done with mutant mice displaying limited diversity of the Ig repertoire due to a severe defect in somatic hypermutation, but having wild-type equivalent intestinal total IgA production, demonstrated that the incapacity to generate antigen-specific antibodies affected immune responsiveness to mucosal challenges as expected, but altered also the microbiota balance.…”

Induction of Oral Tolerance in Neonatal Mice by Transfer of Food Allergens as IgA-Immune Complexes in Breast Milk

“…Recently, IgA-IC has been reported to work as the transporter of antigens through specific IgA receptor and promotes subsequent IgA production and maturation of mucosal immune system [18] [19] [27]. Furthermore, it was also found that the antigen binding to secretory IgA results in decreased sensitivity to intestinal proteases and increased binding to cellular Fc receptors [28], implying the physiological importance of IgA-IC formation. These findings indicated that IgA-IC in breast milk is the most plausible candidate for the inducer of the tolerance in neonates.…”