Ultrastructural characterization of leucocytes in the pronephros of carp (Cyprinus carpio, L.).

In the pronephros of carp (Cyprinus carpio, L.) the following cells were found and ultrastructurally characterized: erythrocytes; lymphocytes and plasma cells; thrombocytes; neutrophilic, eosinophilic and basophilic granulocytes; phagocytic reticular cells and monocytes and non-phagocytic reticular cells. The cells could be separated on a Percoll continuous density gradient and relatively pure fractions could be obtained. In vitro phagocytosis of bacteria (Bacillus megaterium) was found in monocytes and neutrophilic granulocytes, while basophilic and eosinophilic granulocytes engulfed bacterial cells without actual endocytotic uptake.