KILLING OF ISOGENEIC ERYTHROCYTES BY NEUTROPHILS IN GINBUNA CRUCIAN CARP (CARASSIUS-AURATUS LANGSDORFII)

Cytotoxic activity of fish neutrophils against isogeneic erythrocytes is described. Unsensitised neutrophil-rich leucocytes from clonal ginb una crucian carp, separated by density gradient centrifugation, were c ultured with isogeneic erythrocytes. Lysis of isogeneic erythrocytes w as determined by measuring the release of haemoglobin into the superna tant using tetramethylbenzidine (TMB). The level of cytotoxicity obtai ned was proportional to both the content of granulocytes in effector c ell fractions and the effector to target cell ratio. Lysis of isogenei c erythrocytes occurred only after direct contact of neutrophils with target erythrocytes. No erythrolysis was observed when granulocytes an d erythrocytes were cultured in the same medium separated by a polycar bonate membrane, thus allowing exchange of only supernatant but not ce lls. Erythrolysis was therefore not due to a soluble factor released i nto the supernatant by the granulocytes. When erythrocytes and neutrop hils were cultured together by immobilising them in agarose, erythroly sis was only observed microscopically in cases where erythrocytes were in contact with neutrophils. Thus, neutrophils appear able to cause l ysis of histocompatible cells. (C) 1998 Academic Press.