Analysis of the binding and postbinding activities of an inducible cloned CTL line at the population and the single-cell level.

Abstract

We have analyzed the binding and lytic properties of a cloned CTL line before and after induction with MLC SN. Functional, specific binding by both effector populations could be demonstrated to occur at 20 degrees C; however, lysis required temperatures greater than or equal to 30 degrees C. Approximately 50% of noninduced cells and 70% of induced cells formed specific conjugates with P815 target cells. Conjugate formation approached maximum levels by 30 min at 20 degrees C for both populations. When low cell concentrations were employed for conjugate formation, the difference between SN-induced cells and noninduced cells was more pronounced. Analysis of the postbinding abilities of these populations at the single-cell level revealed that SN-induced cells were considerably more efficient in lysing attached target cells than were noninduced cells; however, significant lysis by the latter could be demonstrated after long periods. When populations which had intermediate cytolytic activity were compared to optimally induced or noninduced cells, apparent dissociation of the binding and postbinding capacities was observed. Cells harvested 4 days after stimulation with allogeneic cells plus SN displayed maximal binding but low postbinding activities. These results are consistent with the possibility that multiple components of the lytic mechanism are affected following induction and that these components may be asynchronously modulated.