Gastrointestinal Immunity and Crosstalk with Internal Organs in Fish

The mucosal immune response of teleost fish has gained attention for its key function in developing food tolerance, defining microbiota composition and controlling pathogenic infections. Further, the molecular and cellular contribution of internal organs such as the liver, anterior kidney and spleen to the gastrointestinal immune response has also begun to be deciphered. Experimental evidence for gut-liver axis and gut-kidney axis has recently emerged. In addition, food directly impacts the spleen, via the gastrointestinal system and evidence from farmed fish indicates that a low refined soybean meal diet induces foodborne enteritis. Thus, new studies are needed to identify either novel harmful feed ingredients or additives that can be included in the diets to ameliorate the negative effects triggered by soybean meal. Recently, multidimensional fish cell and organ cultures have proven useful in exploring the interface and crosstalk between metabolism and immunity.

There is significant conservation between mammals and fish in the existing repertoire of innate and adaptive immune cells, as well as in many cytokines. However, despite this conservation and the new data exploring the role of internal organs, their behavior and function in mucosal immunity has yet to be revealed. As fish lack organized gut associated lymphoid tissue, understanding the immune response produced by the gastrointestinal system under different stimuli such as harmful and innocuous food, as well as pathogens and commensal bacteria will shed light on the evolution of the mucosal immune response. It will also allow for the development of strategies and tools to improve the health of farmed fish.

The objective of this Research Topic is to gather new research in the field of gastrointestinal and internal organ immune response, ranging from a basic view, throughout a biomedical perspective to a more applied approach, with a view to the aquaculture industry.

We welcome submissions in the form of Original Research, Methods and Review articles focusing on, but not limited to, the following subtopics:

• Foodborne enteritis and related response of other internal organs in fish
• Modulation of gastrointestinal immunity by both pathogens and commensal bacteria in fish
• The network and crosstalk between intestinal mucosal and systemic immunity in fish
• The crosstalk established through in vitro cell and organ models for gastrointestinal immunity reflected by omics studies, such as the transcriptome, proteome and metabolome.