Abstract: Objective: To investigate the effects of inteluekin-10(IL-10) on the neutrophil phagocytosis and bactericidal activity in mouse model. Methods: Whole blood of mice was pretreated with IL-10 at different concentrations,ranged from 1 pg to 100 ng/ml for 2 hours at 37℃,and then incubated with FITC labeled E. coli at 37℃ for 15 minutes. After lysing red blood cells the neutrophil phagocytosis was measured by flow cytometry. In the bactericidal assay,whole blood of mice pretreated with IL-10(0.1 and 1 ng/ml) for 2 hours at 37℃ was incubated with E. coli in water bath at 37℃ for 1 hour,and then cultured on agar plates. The number of colonies was counted and the inhibitory effect of IL-10 on killing activity was calculated. Results: The reduced rates of phagocytosis was (15.87 ±14.25)% only in the group that pretreated with IL-10 at 1 ng/ml,but with no significance(P > 0.05). The relative rates of bactericidal activity of neutrophil in the groups of IL-10 at 0.1 ng/ml and 1 ng/ml were significanty reduced(39.59 ±37.36)% and (42.28 ±22.24)% (P < 0.05),respectively. Conclusions: IL-10 slightly decreases the phagocytosis of the neutrophils,but potently suppresses the bactericidal activity of neutrophils. IL-10 is capabling of down-regulating non-specific immunity.