The field of mucosal immunology research has grown fast over the past few years, and our understanding
on how mucosal surfaces respond to complex antigenic cocktails is expanding tremendously. With the
advent of new molecular sequencing techniques, it is easier to understand how the immune system of
vertebrates is, to a great extent, orchestrated by the complex microbial communities that live in symbiosis
with their hosts. The commensal microbiota is now seen as the “extended self” by many scientists.
Similarly, fish immunologist are devoting important research efforts to the field of mucosal immunity
and commensals. Recent breakthroughs on our understanding of mucosal immune responses in teleost
fish open up the potential of teleosts as animal research models for the study of human mucosal diseases.
Additionally, this new knowledge places immunologists in a better position to specifically target the fish
mucosal immune system while rationally designing mucosal vaccines and other immunotherapies. In
this review, an updated view on how teleost skin, gills and gut immune cells and molecules, function in
response to pathogens and commensals is provided. Finally, some of the future avenues that the field of
fish mucosal immunity may follow in the next years are highlighted.