On the mucosal surface of the digestive tracts of vertebrates, abundant microbes are allowed to colonize at high densities. Moreover, the type of oropharyngeal microbiota species and the interaction between microbiota and the host immune system in teleosts are still unknown. However, whether the mucosal immune system presents and contains converted role of mucosal immunoglobulin in the oropharyngeal mucosa remains to be determined. It is well-known that in the area at the front of the mammal digestive tract, such as the buccal cavity, secretory IgA (sIgA) mainly from the salivary glands plays an important role in the interaction with oral-associated microbiota and protection of the buccal surface against pathogens ( 6).
Critically, innate and adaptive immune responses can be elicited by immune cells on the teleost posterior by pathogens as in mammals even though they possess different structures ( 5). Moreover, the teleost gut lacks the organized GALT and PP but contains a variety of immune cells, including macrophages, granulocytes, lymphocytes, and plasma cells, in a scattered manner along the alimentary canal ( 4, 5). In contrast to mammals, teleost NALT has only been described as D-NALT in the olfactory organ, while teleost fish lack the choana, and thus the oropharyngeal cavity is a separate compartment from the nasal cavity, but MALT in the teleost pharynx as well as mucosal immune system is poorly investigated.
Based on these, both NALT and GALT form the first immune defense line in the oropharyngeal cavity and gastrointestinal (GI) tract ( 3). GALT, which consists of scattered lymphocytes and organized lymphoid tissues contain Payer's patches (PP), isolated lymphoid follicles and mesenteric lymph nodes ( 1). NALT includes the adenoids, palatine tonsils, and lingual tonsils, as well as a diffuse network of immune cells (D-NALT) ( 2, 3). In mammals, nasopharynx-associated lymphoid tissue (NALT) and gut-associated lymphoid tissue (GALT) and their roles in maintaining mucosal homeostasis in the digestive tract have been well-investigated. As digestive mucosal surfaces represent the main sites in which both environmental antigens and microbiota interact with the host, mucosa-associated lymphoid tissue (MALT) has evolved with a complex and efficient immune system to recognize the non-pathogenic microbiota and prevent the invasion of pathogens ( 1). The digestive tract of vertebrates is responsible for ingesting foods, absorbing nutrition and excreting waste, and therefore it is in continual contact with a complex community of microbiota and environmental pathogens. In addition, the loss of digestive tract dominant species and increased colonization of opportunistic bacteria were discovered in the buccal mucosal surface indicating that a secondary bacterial infection occurred in this mucosal tissue. Moreover, the increased diversity of the microbial community was only detected in the buccal mucosa through 16S rRNA gene sequencing, suggesting that the magnitude of the immune response and microbial community changes are related to the IHNV load and the original microbial diversity.
Hematoxylin and eosin (H & E) and alcian blue (A & B) staining of the trout digestive tract showed that the pathological changes only occurred in the buccal and pharyngeal mucosal tissues. Importantly, following viral infection, we found that the IHNV distribution and the reactions of immune-related genes had similar trends that decreased across the digestive tract. Here, we constructed a bath infection model with infectious hematopoietic necrosis virus (IHNV) in rainbow trout ( Oncorhynchus mykiss). However, in the early vertebrates, the roles of mucosal immune defense and microbial communities in the different segments of the digestive tract are not well-understood. It is widely known that mammals have evolved complex and efficient immune strategies to protect the mucosa of the digestive tract.
Width of mx1 lowrey organ series#
The digestive tract is a unique series of organs that is inhabited by a range of commensal microbes while also exposed to an overwhelming load of dietary antigens.
0 kommentar(er)
