Exogenous ubiquitin inhibits TNF-α secretion of blood and PBMNCs.

(A) Dose-dependent inhibition of TNF-α secretion of human whole blood by exogenous ubiquitin. Whole-blood cultures (in duplicates) from healthy donors (n = 13-18) were incubated for 4 hours with 0 to 1 μg/mL exogenous ubiquitin in the presence of 100 ng/mL LPS. Data represent means ± SEM. *P < .05 versus cultures without ubiquitin. (B) Dose-dependent inhibition of TNF-α secretion of human PBMNCs by exogenous ubiquitin. PBMNC cultures (in duplicates) from healthy donors (n = 10-15) were incubated for 4 hours with 0 to 1 μg/mL exogenous ubiquitin in the presence of 100 ng/mL LPS. Data represent means ± SEM. *P < .05 versus cultures without ubiquitin. (C) Kinetics of the LPS-stimulated TNF-α secretion of human whole blood in the presence of 0 (■), 500 ng/mL (▪), and 1000 ng/mL (●) exogenous ubiquitin. Cultures (in duplicates) were incubated for 2, 4, 8, and 16 hours. (D) Kinetics of the LPS-stimulated TNF-α secretion of 10⁵ human PBMNCs in the presence of 0 (■), 500 ng/mL (▪), and 1000 ng/mL (●) exogenous ubiquitin. Cultures (in duplicates) were incubated for 2, 4, 8, and 16 hours. (E) TNF-α mRNA levels in human PBMNCs stimulated with 100 ng/mL LPS in the presence of 0, 500, and 1000 ng/mL ubiquitin for 2 hours. *P < .05 versus stimulation without ubiquitin. (F) Dose-dependent inhibition of TNF-α secretion of porcine (▪) and murine () whole blood by exogenous ubiquitin. Whole-blood cultures (in duplicates; n = 3) were incubated for 4 hours with 0 to 1 μg/mL exogenous ubiquitin in the presence of 100 ng/mL (porcine) and 1 μg/mL (murine) LPS. Data represent means ± SEM. *P < .05 versus cultures without ubiquitin.