Human secretory immunoglobulin A may contribute to biofilm formation in the gut

Abstract

It is critical, both for the host and for the long-term benefit of the bacteria that colonize the gut, that bacterial overgrowth with subsequent bacterial translocation, which may lead to sepsis and death of the host, be avoided. Secretory IgA (sIgA) is known to be a key factor in this process, agglutinating bacteria and preventing their translocation in a process termed 'immune exclusion'. To determine whether human sIgA might facilitate the growth of normal enteric bacteria under some conditions, the growth of human enteric bacteria on cultured, fixed human epithelial cells was evaluated in the presence of sIgA or various other proteins. Human sIgA was found to facilitate biofilm formation by normal human gut flora and by Escherichia coli on cultured human epithelial cell surfaces under conditions in which non-adherent bacteria were repeatedly washed away. In addition, the presence of sIgA resulted in a 64% increase in adherence of E. coli to live cultured epithelial cells over a 45-min period. Mucin, another defence factor thought to play a key role in immune exclusion, was found to facilitate biofilm formation by E. coli. Our findings suggest that sIgA may contribute to biofilm formation in the gut.

Changes in immunomodulatory constituents of human milk in response to active infection in the nursing infant

“…In addition to transfer of immunoglobulin G to the fetus through the placenta, breastfeeding constitutes an important immunological support that the mammalian mother can provide to her relatively immunocompromised offspring against infections during the first months of life (2-6). The immune system in human milk includes secretory immunoglobulin A (sIgA), immunoglobulin G, free fatty acids, monoglycerides, proteins such as lactoferrin, lactalbumin, glycans, nonabsorbed oligosaccharides, exosomes, immunomodulators such as cytokines, nucleic acids, antioxidants, and immune cells such as macrophages, neutrophils, and lymphocytes (1,4,5,(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17). All these immunologic milk constituents interact together and with the newborn's gut directly or indirectly (e.g., by changing the gut flora) to increase immunity against infection, and probably also contribute to the maturation and efficiency of the newborn immune system (5,6).…”

Recognition of Gram-positive Intestinal Bacteria by Hybridoma- and Colostrum-derived Secretory Immunoglobulin A Is Mediated by Carbohydrates

“…Recently, data demonstrated the induction of strain-specific SIgA secretion following reintroduction of Enterobacter cloacae in the gut of specific pathogen-free mice, indicating a direct impact of this microorganism on the subjacent immune cells (9). Furthermore, SIgA has been described to promote biofilm formation at the gut surface, underlying a straight relationship linking mucosal Abs and the gut microorganisms (10,11). However, the molecular mode of action of SIgA in regulating microbiota colonization remains enigmatic.…”

Development of the intestinal microbiota in the piglet

“…And 90% of plasma cells for IgA and IgM secretions in the lamina propria of the adult pig predominate also until 28 days after birth (Butler and Brown, 1994). Matured immune functions such as secreting self IgA may affect the development of the intestinal microbiota (Bollinger et al, 2003;Kirjavainen and Gibson, 1999). The ingestion of the weaning diet on day 35 also affected the development of the intestinal microbiota.…”