In vitro growth of murine T cells. II. Growth of in vitro sensitized cells cytotoxic for alloantigens

Growth factors (GM), produced by murine lymphoid cells incubated with Concanavalin A, have been used to grow cytotoxic lymphoid cells in culture. C57BL/6 and DBA/2 lymphoid cells were sensitized against each other in primary, secondary, and tertiary in vitro cultures. These sensitized cells were grown in vitro in GM and retained their cytotoxic properties. Cells grew in culture about 10-fold every 5 to 7 days for over 2 months. Initial growth of cytotoxic cells in GM resulted in marked enhancement of specific cytotoxicity that returned to original levels after subsequent subcultures. After five 10-fold cell culture generations some nonspecific cytotoxicity directed against the responding target cell strain appeared in continuous cultures. This technique for growing large numbers of cytotoxic cells may be of value in the development of adoptive immunotherapies.