Ontogenic development of the kidney, thymus and spleen and phenotypic expression of CD3 and CD4 receptors in lymphocytes from the Cobia Rachycentron canadum
The Cobia Rachycentron canadum, has several favorable characteristics for aquaculture, such as high growth rate, good coefficients of food efficiency and excellent quality meat, among others. In the present study, an analysis of the immune system of Cobia was performed using histology and immunohistochemistry techniques. The ontogeny of the immunocompetent organs (anterior kidney, thymus and spleen) in larvae and juvenile bijupira, from hatching to 53 days after hatching (aids), was performed through histological analysis. The kidney was the first lymphohematopoietic organ to appear, present on the 1st day after hatching (dae) (3.8 ± 0.04mm), the appearance of the spleen was on the 5th dae (4.8 ± 0.2mm) and on the 7th dae (5.4 ± 0.2 mm) the latter; according to the analysis, the lymphoid organs became evident with the advancing age of the fish.It was also possible to establish the presence of specific lymphocyte receptors through immunostaining with monoclonal anti-CD3 and anti-CD4 antibodies. The first CD3 lymphocyte receptors were found in the thymus at the 7th day with 27% mm² and 99% mm² of thymic tissue at 53 days (154 ± 4.6 mm). The phenotypic expression of CD3 receptors in the kidney was highlighted on the 8th day (6.5 ± 0.1 mm) with an expression of 10% mm² and 32% mm² of renal tissue at 53 dae. The immunostaining of CD4 lymphocyte receptors was initially highlighted in the thymus with 7 dae, with 5% mm² and at 53 dae with 63% mm² of lymphocytes immunostained with anti-CD4. In the kidney, the T4 lymphocyte population was first recorded at 13 th aids (12.4 ± 0.7 mm) with 9% mm² and at 53 aids with 28% mm² of the CD4 lymphocyte population of the renal tissue, defining the functional development of the system specific,associated with the capacity of immune memory. It was also possible to establish that T lymphocyte repopulation occurs in the anterior kidney, the lymphocytes that migrate from the anterior kidney to the thymus and acquire specific T cell receptors, returning to the anterior kidney and maintaining their immune activities. The study of the mechanisms of the immune system is important for the success of a culture, since diseases are one of the main causes of economic losses in aquaculture worldwide.