About this Research Topic
Mucosal immunity is now one of the hottest topics among fish scientists working in a wide range of disciplines. So far, in several teleosts species it has been clearly demonstrated the presence of a full set of immune cells necessary to elicit strong immune responses at the mucosal sites like the gills, gonads, gut and skin. These sites are collectively regarded as mucosal associated lymphoid tissues (MALT). However, the study of such structures in fish need special attention due to the fact they are functionally different from the more commonly studied mammalian counterparts. Particularly, at the intestine, a recently described fish specific immunoglobulin isotype IgT/IgZ has turned even more attractive the immune output of this organ. The IgT/IgZ, which resembles the mammalian IgA, is of particular interest to perform basic, developmental and comparative fish gut functional analyses. Nevertheless, it is suspected that IgT may have a relevant role in different areas dominated by MALTs, but further investigation is required. Among, the main functions of such active immunological sites are to protect the host against exposure to pathogens by means of the immune properties of the mucus, but also to avoid hypersensitivity reactions to food proteins, commensal microflora or to immune modulators (pre/probiotics, immunostimulants and vaccine adjuvants), which are frequently used in aquaculture as means to increase disease resistance. Several research papers claim the effective use of these immune modulators such as immunostimulants or vaccine adjuvants that target the innate immune responses while others, like probiotics, have found use as a means of disease control by excluding competition from pathogenic microbes, inhibiting pathogen adhesion and maintaining the correct organization of the tight junction and cytoskeleton proteins. Prebiotics, which are mostly non-digestible carbohydrates, have shown promise as treatments for several diseases in both clinical and animal studies. However, an understanding of the molecular mechanisms behind the direct and indirect effects on the mucosal immune responses should be addressed by using the latest outputs generated by the state-of-the-art omics sciences. These will enhance the possibilities to use in a targeted fashion such immune tools on increasing disease resistance against several pathogens at aquaculture facilities. Thus, the objective of this Frontiers Research Topic is to review from a mucosal perspective, the current state of immune modulators in aquaculture, establish new ideas, propose hypothesis on how immune mechanisms could be potential to gain disease resistance; and propose future directions to achieve altogether outstanding knowledge on this fascinating but not well understood topic.
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