[Comparison of macrophages and dendritic cells infected by Brucella S(2)]

Objective To make a comparison of the characteristics between macrophages and dendritic cells (DC) infected by Brucella suis (B. suis) S(2);. Methods Wrights-Giemsa's stainning was used to observe the cell morphology and calculate the phagocytic rate. ELISA was employed to detect the expressions of IL-12 and TNF-α in cell culture supernatants as well as the contents of IFN-γ and IL-4 in the co-culture with T cells. With annexin-V-FITC/PI double staining, the cell apoptosis rate was determined by flow cytometry. Results 1 h after infected by B. suis S(2);, the phagocytic rate of macrophages was (43.6±4.8)%, which was significantly higher than that of the DC (16.3±2.7)% (P<0.05). The apoptosis rates of normal macrophages and macrophages 6, 12 and 24 h after infected by B. suis S(2); were (3.09±1.21)%, (19.89±1.36)%, (22.73±2.21)% and (42.44±3.12)%, respectively, which were dramatically higher than those of the DC at the corresponding time points, being (1.82±0.01)%, (3.76±0.13)%, (7.87±0.56)% and (9.08±0.23)%, respectively (P<0.05). The levels of IL-12 secreted by macrophages 24 and 48 h after infected by B. suis S(2); were significantly lower than those by the DC (P<0.01). At 24, 48 and 72 h, the levels of TNF-α secreted by macrophages were dramatically lower than those by the DC (P<0.01), and the levels of IFN-γ in the co-culture supernatants of macrophages and T cells were significantly lower than those in DC and T cell co-culture (P<0.01). Conclusion Macrophages have a better ability in phagocytosing B. suis S(2); than DC and the apoptosis rate of macrophages is higher than that of DC after infected by B. suis S(2);, but in activating and inducing the cellular immune response and presenting antigen, DC are stronger than macrophages.