ABSTRACT
Objective To determine the effect of interferon-gamma (IFN-γ) on the phagocytosis and killing activity of a murine macrophage cell line RAW264.7 against T.asahii,and to estimate the possibility of treating T.asahii infection with IFN-γγ.Methods T.asahii was cultured with or without the presence of different concentrations (10,100,1000 U/ml) of IFN-γfor 18 hours followed by the incubation with RAW264.7 cells for different durations.After additional culture for 45 minutes,the number of T.asahii cells phagocytosed by RAW264.7 cells was counted under an inverted microscope,and the rate of phagocytosis was calculated.The number of colony forming units of T.asahii per milliliter (cfu/ml) was counted after 4-hour additional culture and the growth inhibition rate was determined.Data were processed by the SPSS 16.0 software,and comparisons of parameters between these groups were done by Bonferroni method and analysis of variance after homogeneity test of variance.Results The number of phagocytosed T.asahiicells was 25.12 ± 1.81,35.88 ± 3.56,52.12 ± 3.23,with the phagocytosis rate being 25.12％,35.88％ and 52.12％,respectively in RAW264.7 cells incubated with IFN-γ of 10,100,1000 U/ml,significantly different from that in untreated RAW264.7 cells (13.62 ± 2.39,13.62％,all P ＜ 0.01).The colony forming units of T.asahii per ml after incubation with untreated RAW264.7 cells differed significantly from those after incubation with IFN-γ (10,100,1000 U/ml)-treated RAW264.7 cells ((68.12 ± 3.39) × 500 vs.(58.62 ± 4.89) × 500,(45.50 ± 3.02) × 500 and (34.62 ± 4.24) × 500,all P＜0.01),with the growth inhibition rate being 25.21％,41.95％ and 55.83％ respectively for RAW264.7 cells incubated with IFN-γ of 10,100,1000 U/ml.Statistical differences were also observed in the killing activity between RAW264.7 cells incubated with different concentrations of IFN-γ (all P ＜ 0.01).Conclusion IFN-γ (10-1000 U/ml) may enhance the phagocytosis and killing activity of RAW264.7 cells against T.asahii in a concentration-dependent manner.