Specialization of mucosal immunoglobulins in pathogen control and microbiota homeostasis occurred early in vertebrate evolution

Mucosal surfaces in teleost fish harbor B cells that produce IgT, a secretory mucosal immunoglobulin. To investigate how IgT influences gill microbiota composition and resistance to infection, Xu et al. developed an efficient technique for temporarily depleting IgT-producing B cells in rainbow trout. Acute induction of IgT deficiency in trout led to dysbiosis of commensal gill microbiota, inflammation, tissue damage, and impaired resistance to infection by a mucosal parasite.