Reversible changes in cytolytic T lymphocyte function induced by hyperthermia

The ability of cytolytic T lymphocytes (CTL) generated in vitro in mixed leucocyte cultures (MLC) to "repair" functional damage induced by moderate hyperthermia has been investigated. Repair of CTL function was assessed in a split dose system in which MLC cells were exposed to a total of 20 min at 43 degrees C delivered either as a single treatment or as two 10 min fractions separated by an interval at 37 degrees C. Significant repair was observed within 15 min at 37 degrees C in the split-dose protocol and maximum repair (corresponding to a 30-100-fold increase in lytic activity) was seen after 1.5-2 h. Repair was both temperature and energy dependent and was apparently related to a reversible lesion in the cytolytic mechanism itself. The effect of a number of metabolic inhibitors (and other agents) on repair was determined, but the precise nature of the heat-induced lesion could not be identified.