Immunocytochemical detection of thymocyte antigenic determinants in developing lymphoid organs of sea bass Dicentrarchus labrax (L.).

The monoclonal antibody DLT15 specifically recognised antigenic determinants expressed during development of thymic lymphoid cells of the sea bass Dicentrarchus labrax (L.). They were first detected at day 30 post-hatching in the thymus of fish maintained at 16) C; thereafter, a marked increase in the number of immunoreactive cells occurred mostly in the outer region of the thymus. The appearance of DLT15-immunoreactive cells in the lymphoid organs was in the sequence thymus, head-kidney and spleen. The thymus thus appears to be a primary lymphoid organ in the sea bass. Infrequent cells sharing the antigenic determinants expressed on thymocytes were localised in the developing head-kidney and spleen.