Immunohistochemical characterization of lymphocyte populations in carp (Cyprinus carpio L.).

Surface immunoglobulin-bearing cells from peripheral blood, thymus, head kidney, and spleen in carp (Cyprinus carpio L.) were studied by immunoperoxidase labelling using antisera against fragments of carp IgM. Different lymphoid cell populations could be determined. Thus, about 35% of the lymphocytes of the peripheral blood, head kidney, and spleen were determined, as "B" lymphocytes, using rabbit anti-carp Fab antiserum with L chain specificity. Nearly all lymphocytes of the peripheral blood, head kidney, and spleen are bearing immunoglobulin determinants or cross-reactive structures. The latter also holds true for about 98% of thymocytes. The differences between the Ig-like surface structures of the thymocytes and the membrane-bound immunoglobulins of a population of lymphocytes are discussed.