Cytotoxic Potential of Stimulated

Lymphocytes from tmsensitized animals or humans damage allogeneic cells in tissue culture when aggregated to the latter by means of phytohemagghtinin (PHA) (1-3). Under the experimental conditions used, injury of the target cells was not seen or was slight in the absence of PHA. When the PHA-treated lymphocytes were separated from the target cells by a Millipore falter, cell damage was prevented (1). Moreover, extracts from PHA-treated eells did not damage the tissue culture ceils (1). Therefore, close contact between living lymphocytes and target cells seemed to be necessary for a cytotoxic reaction. However, PHA is also known to stimulate lymphocytes, leaxiing to transformation into blast cells and mitosis (4, 5). Hence, it could be assumed that a PHA-induced stimulation of lyrnphocytes could contribute to their cytotoxic action.