Roles of Secretory Immunoglobulin A in Host-Microbiota Interactions in the Gut Ecosystem

Abstract

In the gastrointestinal tract (GIT), the immune system interacts with a variety of microorganisms, including pathogens as well as beneficial symbionts that perform important physiological functions for the host and are crucial to sustain intestinal homeostasis. In normal conditions, secretory immunoglobulin A (SIgA) is the principal antibody produced by B cells in the GIT mucosa. Polyreactivity provides certain SIgA molecules with the ability of binding different antigens in the bacterial surface, such as O-antigens and teichoic acids, while cross-species reactivity allows them to recognize and interact with different types of bacteria. These functions may be crucial in allowing SIgA to modulate the complex gut microbiota in an efficient manner. Several studies suggest that SIgA can help with the retention and proliferation of helpful members of the gut microbiota. Gut microbiota alterations in people with IgA deficiency include the lack of some species that are known to be normally coated by SIgA. Here, we discuss the different ways in which SIgA behaves in relation to pathogens and beneficial bacteria of the gut microbiota and how the immune system might protect and facilitate the establishment and maintenance of certain gut symbionts.

Nutrition, Gut Microbiota, and Allergy Development in Infants

“…However, different bacteria induce IgA production at different levels, and also seem to interact with this antibody in different ways. IgA has the capacity to engage in a variety of asymmetrical interactions with different bacterial types, potentially contributing to promoting the retention of habitual gut symbionts while ensuring containment or clearance of opportunistic pathogens [ 66 ]. For instance, interactions between IgA N-glycans and peptidoglycans in the cell wall envelope of beneficial Gram-positive species of the Firmicutes and Actinobacteria appear to favor their retention in the intestine.…”

The Role of the Gut Microbiome in Cow’s Milk Allergy: A Clinical Approach

“…The main function of sIgA, referred to as immune exclusion, is to limit the access of pathogens and food allergens to the mucosal barrier, and thus prevents their spread to the systemic compartment [ 82 ]. In addition, it regulates the balance of gut microbes by favoring the maintenance of beneficial members and the removal of opportunistic pathogens, which in turn prevents the absorption of pathogens and toxins [ 83 , 84 ]. There is evidence that mucosal secretion of sIgA is partially controlled by the gut microbiome and even that specific microbial species can induce its production to a different extent [ 84 ].…”

“…In addition, it regulates the balance of gut microbes by favoring the maintenance of beneficial members and the removal of opportunistic pathogens, which in turn prevents the absorption of pathogens and toxins [ 83 , 84 ]. There is evidence that mucosal secretion of sIgA is partially controlled by the gut microbiome and even that specific microbial species can induce its production to a different extent [ 84 ]. As a result, the composition of gut microbes strongly influences sIgA production and, consequently, the development of oral tolerance.…”

Research Progress on the Therapeutic Effect of Polysaccharides on Non-Alcoholic Fatty Liver Disease through the Regulation of the Gut–Liver Axis

“…Yang et al [ 69 ] found that intestinal sIgA production was reduced in NAFLD/NASH rats, suggesting that IgA had a potential function in liver disease. There were other reports that sIgA helped to protect beneficial members of GM and had a special coating ability for Gram-negative bacteria to prevent them from adhering to the intestinal wall, thereby exerting a protective function on the intestinal barrier [ 70 , 71 ]. Conversely, when the intestinal mucosa is damaged, the number of sIgA plasma cells decreases, which may aggravate intestinal bacterial translocation [ 72 ].…”