Interindividual variability and intraindividual stability in T-cell function and different susceptibility towards calcineurin inhibitors. (A) Inter-individual variability of SEB-reactive T-cell frequencies in 30 healthy controls (50.27 ± 13.5 years of age; 15 females), 30 short-term (51.71 ± 12.80 years of age; 15 females) and 30 long-term transplanted patients (50.16 ± 13.31 years of age; 14 females) is shown. Medians are indicated by horizontal lines and did not differ between the groups (Kruskal-Wallis test with Dunn’s post test). Intra- and inter-assay variability in SEB-reactive T-cell frequencies stimulated from blood samples of five healthy volunteers (P1-P5; 35.34 ± 5.54 years of age; 2 females) in the absence (B and C) or presence of 67 ng/ml tacrolimus (D and E) or 1111 ng/ml cyclosporine A (F and G). Intra-assay variability of T-cell reactivity was determined by repeated measurements of the same blood sample (B, D, and F). Inter-assay variability of T-cell reactivity was determined in three independently collected blood samples (0, two and six weeks; C, E, and G). The inhibitory effect on T-cells by calcineurin inhibitors was compared in relation to the samples treated without drugs. All drugs were solved in ethanol. Mean values are indicated as horizontal lines in panels B-G.