Th9 cells in allergic diseases: A role for the microbiota?

Abstract

Since their discovery about 10 years ago, Th9 cells have been increasingly linked to allergic pathologies. Within this review, we summarize the current knowledge on associations between Th9 cells and allergic diseases and acknowledge Th9 cells as important targets in future treatment of allergic diseases. However, until today, it is not fully understood how these Th9 cell responses are modulated. We describe current literature suggesting that these Th9 cell responses might be stimulated by microbial species such as Staphylococcus aureus and Candida albicans, while on the other hand, microbial and dietary compounds such as retinoic acid (RA), butyrate and vitamin D show suppressive capacity on allergy‐related Th9 responses. By reviewing this recent research, we provide new insights into the modulating capacity of the microbiota on Th9 cell responses. Consequently, microbial and dietary factors may be used as innovative tools to target Th9 cells in the treatment of allergic diseases. However, further research is needed to elucidate the mechanisms behind these interactions in order to translate this knowledge into clinical allergy settings.

Go With Your Gut: The Shaping of T-Cell Response by Gut Microbiota in Allergic Asthma

“…Alternatively, Tregs polarization could be promoted by an IL-10 dependent pathway from microbiota-derived antigen presentation by dendritic cells (DCs) (6). Several other Th subsets such as Th9 (7) and Tregs subtypes (8) are implicated in allergic responses while their relationship with the gut microbiota is not entirely defined. Furthermore, the role of Th17 in AAS was heavily investigated (9) and they are currently recognized as one of the crucial mediators of AAS.…”

Vitamin D and Microbiota: Is There a Link with Allergies?

“…The human microbiota is the community of commensal, symbiotic, and pathogenic microorganisms that survive on our body, skin, and respiratory, gastrointestinal and urogenital systems [ 6 ]. The composition of the microbiota is already formed in the early years of life but is dynamic and shaped by both genetic and non-genetic factors [ 2 ]. The microbiome is the set of genomes of our microbial symbionts [ 7 ].…”

“…In addition to the maternal vaginal and intestinal flora, breast milk also helps to shape the infant microbiome, as it is heavily enriched with germs. The gut microbial community is the most abundant [ 2 ] and the vast majority of microbiota in the human gastrointestinal tract live in the colon: The gut contains a large and diverse population of microorganisms that is, quantitatively, the most important postnatal source of microbial stimulation of the immune system. Anaerobes (particularly Firmicutes and Gram-positive Actinobacteria and Gram-negative Bacteroidetes ) are the predominant bacteria in the gastrointestinal tract of adults [ 11 ].…”

“…It has been shown that the effects of microbial factors derived from the intestine are not limited to the intestinal microenvironment, but also to the immune cells of other organs, through the so-called intestine–lung, intestine–brain, and intestine–bone axes, and others. These broad effects could be mediated by the release of metabolites produced by the gut microbiota into the circulation or by the trafficking of gut-derived activated T cells to other compartments of the body [ 2 ]. As a result, the gut microbiota could affect the whole organism′s immune system.…”

“…Research indicates that the microbiota exhibits both pro-inflammatory and anti-inflammatory properties in direct or indirect ways [ 1 ]. It is now clear that alterations of the normal composition of the microbiome are narrowly associated with immunological disorders [ 2 ]. Vitamin D is a fat-soluble vitamin and a critical regulator of calcium and phosphate homeostasis and bone health [ 3 ].…”