CYTOTOXICITY REACTIONS IN THE SOLITARY TUNICATE STYELA-PLICATA

Hemocytes from the tunicate, Styela plicata, undertake cytotoxic respo nses toward human K562 tumor cells or rabbit red blood cells (RRBC), R eactions to both target cell types were found to require metabolic act ivity. However, it was not determined whether killing involves soluble factors or direct cell/cell contact, Differences in the response to v aried effector:target ratios indicate that reactions against the K562 cells and RRBC are mediated by separate mechanisms, The existence of t wo discrete cytotoxic mechanisms was supported by experiments which de monstrated that pharmacological treatments have different effects on t he cytotoxic destruction of K562 cells and RRBC, Moreover, cytotoxic r eactions toward the different targets cells were shown to be mediated by different hemocyte sub-populations isolated from hemolymph by densi ty gradient centrifugation.