Fig. 3.

Down regulation of Ni-induced cytokine production in Ni-PBMC by recombinant IL-10. PBMC were incubated with 50 µM NiCl₂ and a concentration range of rIL-10 followed by analysis of IL-13 and IFN-γ levels by (a) ELISA or (b) number of IL-4-, IL-13- and IFN-γ-producing cells by ELISpot. The effect of rIL-10 on the Ni-induced cytokine increment was calculated by subtracting the spontaneous cytokine production in the presence of rIL-10 from the Ni-stimulated cytokine production in the presence of the corresponding concentration of rIL-10. ○ (n = 8) and • (n = 7) represent Ni-reactive donors with levels of Ni-induced IL-10 < 30 pg/ml or > 30 pg/ml, respectively. Mean responses are indicated as horizontal bars. Statistical differences between the Ni-induced cytokine production in the absence of rIL-10 and after addition of different concentrations of rIL-10 following a Wilcoxon matched pairs test are depicted with asterisks (*P < 0·05, **P < 0·01, ***P < 0·001).