Channel catfish cytotoxic effector cells from peripheral blood and pronephroi are different

Although rapid progress has been made in knowledge of the teleost immune system, specific antibodies recognizing cellular populations are few and, among lymphocytes, they are restricted to the B cell lineage. In this work, we describe the preparation and characterisation of a monoclonal antibody directed against thymocytes of the mediterranean sea bass (Dicentrarchus labrax) (1 year group). The antibody was obtained by immunising mice with paraformaldehyde-fixed thymocytes, and by screening hybridoma culture media by indirect immunofluorescence and FACS analysis using both fixed and living cells. The hybridoma cell line which after limiting dilution cloning gave the best IIF staining of living thymocytes, and the sharpest immunostaining of Bouin fixed sections was selected and named DLT15. DLT15 stained 74·9% of thymocytes, 2·4% of cells in the whole blood, 0·8% in the spleen, and 2·6% in the head-kidney in immunofluorescence and FACS analysis. Immunohistochemical analysis revealed DLT15-immunoreactive cells inside the thymus, the spleen, and the head-kidney. In these two latter organs immunoreactive cells were enriched in regions where erythropoiesis was less abundant, and were present either as isolated cells or as small clusters of two to four cells.