Cytotoxic activity against prelabelled RTG-2 cells in the turbot, Scophthalmus maximus (L.)

Leucocytes derived from head kidney, blood and spleen of turbot, Scophthalm us maximus (L.), exhibited cytotoxic activities against an established cell line (RTG-2) derived from rainbow trout, Oncorhynchus mykiss (Walbaum). Th e optimal effector:target ratio, temperature and incubation period for the activity was determined. Cytotoxicity was not caused by released factors, a s effector:target contact was needed. Visualization of the cultures under t he transmission electron microscope corroborated the contact between leucoc ytes and target cells and suggested the implication of monocyte-like cells in this cell-mediated cytotoxicity.