Mucosal immunoglobulin response in Epinephelus coioides after Cryptocaryon irritans infection

The teleost mucosal immune system consists mainly of the skin, gills and gut, which play crucial roles in local immune responses against invading organisms. Immunoglobulins are essential molecules in adaptive immunity that perform crucial biological functions. In our study, a mucosal immunity model was constructed in Epinephelus coioides groupers after Cryptocaryon irritans infection, according to previous experience. Total IgM and IgT in the groupers increased in the serum and mucus in the immune group, whereas only pathogen-specific IgM were detected existence. More critically, pathogen-specific IgM was detected in the head kidney, gill and skin supernatants, thus suggesting that the systematic immune and mucosal immune system secreted immunoglobulins. Furthermore, an early response in the skin was observed, on the basis of the detection of pathogen-specific IgM in the skin supernatant. In conclusion, this research characterized the grouper IgM and IgT in mucosal immune responses to pathogens in the gills and skin, thus providing a theoretical basis for future studies on vaccines against C. irritans.