The effect of culture temperature on the kinetics of human lymphocyte stimulation by phytohaemagglutinin.

The effect of varying the culture temperature on the growth kinetics of human lymphocytes stimulated by phytohaemagglutinin (PHA) has been studied by a new method using a Coulter Channelyzer. Each of three subjects had a distinctive percentage of responding cells (P less than 0.01), greater after 22 hr culture than after 15 hr (P less than 0.05) due to continued recruitment, but these values were unmodified by variation of the culture temperature in the range 35 degrees C--39 degrees C. The incremental growth rate is the major descriptor of cellular growth and, not unexpectedly, each subject has a distinctive value (P less than 0.01) which is greater after culture for 22 hr than after 15 hr (P less than 0.05). We attribute the increase to the effect of recruitment in modifying the mean value of this parameter. These growth rates were similar at 35 degrees C and 37 degrees C (P less than 0.01), but higher at 39 degrees C (P less than 0.01). Lymphocytes cultured at 41 degrees C failed to grow satisfactorily in either the control or PHA-stimulated wells and it was obvious that cells were damaged at this temperature. Our results establish that PHA-stimulated lymphocytes grow more quickly at 39 degrees C than at 37 degrees C in the early stages of the first cell cycle, but that there is no increase in the number of responding cells at the higher temperature. The results suggest that moderate fever might have a beneficial effect on lymphocyte responses to infection.