[Response of mouse macrophage cell line infected with Bacille Calmette-Guerin in vitro]

To illuminate the response of mouse macrophage cell line RAW264.7 after infected with Bacille Calmette-Guerin (BCG) in vitro.

We analyzed the morphology and expression of co-stimulatory molecules on the surface of RAW264. 7 after exposure to BCG for 23 hours. Then during the different culture time after discard the BCG in the supernatant, we analyzed the response of RAW264. 7 by flow cytometry using carboxyfluorescein diacetate, succinimidyl ester (CFDA-SE), annexin V/PI and Rhodamine 123, respectively.

We observed the phagosome containing BCG under transmission electronic microscope and RAW264. 7 cells still grow well after incubated with BCG for 23 hours. We found that the expression level of co-stimulatory molecules, CD40, CD54, CD80, CD86 and CD11b, were elevated evidently, except CD11c, I-A(d) and H-2K(d). The fluorescence intensity of BCG stained with CFDA-SE decreased with the prolongation of culture time, but it was still more higher than unstained control four days later. After removal of uninfected BCG, the percents of BCG-infected cell decreased and we didn't detected BCG-infected cells evidently for 60 h culture. Furthermore, we also found that there was no obvious cell apoptosis for all the time, and the mitochondrial membrane potential of BCG-infected cells increased early and then decreased to the same level as the uninfected control.

These results would be helpful to elucidate the mechanism of BCG vaccination.