Differential circadian rhythm of T-cell function in transplant recipients and healthy controls. Circadian rhythm of SEB-reactive CD4 T-cell numbers in peripheral blood of healthy controls (n = 6), long-term (n = 12) and short-term transplanted patients (n = 7) was determined over 24 hours at 8:00 a.m., 12:00 p.m., 8:00 p.m., 12:00 a.m. and the following day 8:00 a.m. Shown are the differences in absolute cell numbers of IFN-γ positive (A) and IL-2 positive (B) CD4 T-cells with respect to the mean that was calculated from all values analyzed over the 24 h-time period (stippled line). The variance of cytokine-producing T-cells at each time point with respect to this 24 h-mean is expressed as mean ± standard error of the mean. Statistical analysis was performed using the repeated measures ANOVA with Tukey’s post-test. Statistically significant differences are indicated with respect to the initial 8:00 a.m. sample. *p < 0.05, **p < 0.01, ***p < 0.001.