IgM-producing cells distribution in spleen and head kidney of pejerrey (Odontesthes bonariensis)

VIGLIANO, F.A.; BERMÚDEZ, R.; QUIROGA, M.I.

Vigo

Congreso; First International Conference of Fish and Shellfish Immunology; 2013

International Society of Fish and Shellfish Immunology/Consejo Superior de Investigaciones Científicas (España)

Pejerrey (Odontesthes bonariensis) is one of the most important fish species cultured in Argentina due to the quality of its flesh, its abundance in lagoons of Pampa Plain, and its high value in recreational fishing. Although, traditionally the purpose of pejerrey aquaculture in Argentina was the production of embryonated eggs and fry for seeding and reseeding in the last decade, the commercial interest in pejerrey culture has been increased. A drawback to its development is the lack of information about frequent diseases affecting this species, and particularly, on the immune response of the species against diseases. A key effector cell in acquired immunity is the plasma cell or IgM-producing cell (IgM+-cells).The aim of this work was to establish the organ distribution of IgM+-cells in the main haemolymphopoietic organs of pejerrey, the head kidney and spleen, by means of immunohistochemistry. Twenty healthy adult fish were euthanised and samples of both organs were taken, fixed in Bouin´s fluid, and embedded in paraffin wax. An indirect immunoperoxidase staining was performed using a rabbit polyclonal antiserum against turbot IgM. In spleen, the percentage of IgM+-cells associated to blood vessels or melano-macrophages centres (MMCs) were calculated. In addition, the percentage of MMCs associated to IgM+-cells were recorded in both organ. Significant differences (p less than 0.05) between structures or organs were assessed by a Mann-Whitney test. In spleen, IgM+-cells were mainly distributed along blood vessels (88.3%) with significant differences (p = 0.0079) in comparison to those located around MMCs (11.7%). The most frequent splenic vessels linked to IgM+-cells were the ellipsoids. On the contrary, IgM+-cells located in head kidney did not show a defined pattern correlated to an specific structure and they were frequently seen scattered through the intertubular tissue. In relation to the percentage of MMCs associated to IgM+-cells, values in head kidney (10%) were significantly lower (p = 0.0317) than those observed in spleen (53%). The differential distribution in IgM+-cells between organs may indicate a primary role of spleen as a site for development humoral immune response in adults of O. bonariensis since several authors reported variations in functions or properties of MMCs in spleen and head kidney.