Isolation of alloreactive CTL clones with cyclical changes in lytic activity.

We have isolated two H-2Dd specific CTL clones from CBA anti-DBA/2 MLC that undergo changes in lytic activity against tumor and Con A blast target cells as a consequence of weekly stimulation with irradiated allogeneic cells and conditioned medium from secondary MLC. Lytic activity is highest on days 2 to 3 after stimulation, and lowest on days 5 to 7. CTL that had been irradiated on day 0 before stimulation have significantly greater activity on day 2. Conditioned media alone, in the absence of added allogeneic stimulator cells is capable of supporting, in a dose-dependent fashion, the increase in activity. Collectively, these changes are similar to those described for the induction of lytic activity in nonlytic CTL populations from long-term MLC, and suggest that these cloned lines may be useful to study the modulation of lytic activity of CTL in culture.