Stability of individual differences in cellular immune responses to two different laboratory tasks

To explore the stability of immune reactivity across laboratory tasks, we correlated enumerative and functional lymphocyte responses to a speech task and a mental arithmetic task, delivered on the same occasion of testing in 31 healthy undergraduates. Both tasks were associated with an increase in peripheral CD8+ and CD56+ cell populations, and a decrease in proliferative response to phytohemagglutinin (PHA) and ratio of CD4:CD8 cells. Intertask correlations were significant for the magnitude of change in proliferative responses at two different concentrations of PHA, r = 0.76, p < .0001 and r = 0.46, p < .05, and in numbers of circulating CD56+ cells, r = 0.46, p < .005. Concomitant heart rate and systolic blood pressure responses also correlated significantly over the two experimental tasks (heart rate: r = 0.52 and systolic blood pressure: r = 0.58. ps < .0005). These data provide initial evidence that interindividual variability of some cellular immune responses is moderately reproducible across different stimulus conditions, providing further evidence that it may denote a stable individual difference.