Fish Can Mount a Local IgT Antibody Response to Pathogens & Microbiota Within Their Gills; Finding Has Implications for Fish Vaccines & Evolution

Oriol Sunyer, Ph.D., a professor at the University of Pennsylvania School of Veterinary Medicine, has described fish as "an open gut swimming." Their mucosal surfaces -- their skin, digestive tract, and gills -- are in constant contact with water, including any pathogens that that water may contain. In aquaculture facilities, this exposure is a risk, as diseases can quickly tear through populations. In hopes of improving vaccines that keep fish healthy, researchers are therefore very interested in learning how fish detect and respond to pathogens through their mucosal surfaces. There is also great interest in learning how fish control the community of "friendly" microbes, the microbiota, that dwell in and on their respiratory surfaces. In a new study published in the journal Nature Communications, Dr. Sunyer and colleagues made headway in this understanding. Their work reveals that fish induce the production of a particular antibody class in their gills in response to pathogen exposure. In addition, the researchers found that the gills' microbiota is coated with this same class of antibody, called IgT, the function of which was first discovered by Dr. Sunyer's lab in 2010. Prior to the current study, it was thought that only mammals had such a refined local mucosal immune response. The open-access Nature Communications article is titled “Mucosal Immunoglobulins at Respiratory Surfaces Mark an Ancient Association That Predates the Emergence of Tetrapods.” "Our work is the first to show that fish can mount a local antibody response to pathogens and microbiota within a mucosal respiratory surface," Dr. Sunyer said. "We might expect that mucosal immunoglobulins play a key role in controlling the microbiota in mammals' lungs as well, which is something that has yet to be explored." In previous work, Dr.
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