Intestinal immunity of dogfish Scyliorhinus canicula spiral valve: A histochemical, immunohistochemical and confocal study.

The present study describes histochemical and immunohistochemical characteristics of the spiral valve and its associated lymphoid tissue (GALT) in the dogfish Scyliorhinus canicula. The mucosal surface of the spiral valve represents the first line of defense against pathogens coming from the external environment through food. Epithelial, mucus and immune cells play a key role in controlling the inflammatory response. Valve intestine of S. canicula had many folds lined by simple columnar cells and goblet cells, which later reacted positive to PAS, AB and AB-PAS, histochemical stains differentiated the different types of mucins; lectin histochemistry (PNA and WGA), detected neutral and acid mucins secreted that plays an important role in protection against invading pathogens. Integrin α5β1 was expressed in enterocytes that line the valve's folds with greater marking in the apical part of the cells. Laminin was found on the apical side of the epithelium, in fibrillar and cellular elements of the lamina propria and in the muscularis mucosa. In the spiral valve gut-associated lymphoid tissue (GALT) has been studied. For the first time, massive leucocytes aggregates were identified by confocal immunofluorescence techniques, using the following antibodies: TLR2, S100, Langerin/CD207. Our results expand knowledge about Dogfish valve intestine giving important news in understanding comparative immunology.