Two natural killer-cell subpopulations distinguished by heat sensitivity

We examined the effect of heat on natural killer-cell activity and found that two different natural killer-cell subpopulations can be distinguished by their heat sensitivity; one subpopulation loses natural killer-cell activity at 41 degrees C, and the other is not affected. In a single-cell assay, the ability of natural killer cells to conjugate to K 562 cells was not affected by incubation at 41 degrees C, but the killer activity of natural killer cells after conjugating to K 562 cells was reduced at 41 degrees C. Therefore it is likely that the difference in heat sensitivity between the two subpopulations is due to postbinding cytolytic events. Tetracaine, which influences cytolytic events, was used to examine whether or not the two natural killer-cell subpopulations can be distinguished by tetracaine sensitivity. However, it was found that tetracaine inhibits natural killer-cell activity equally for both of these natural killer-cell subpopulations.