The In Vitro M1/M2 Polarization of Macrophages of BCG-Infected Mice.

Cultured peritoneal macrophages from intact (control) and BCG-infected (experiment) male BALB/c mice were studied 90 days after infection. Polarization of macrophages by M1 (expression of GM-CSF, IFNγ, and CD16/32) and M2 (expression of bFGF and CD36) differentiation pathways was studied with consideration for their the nuclearity class. Mononuclear cells predominated (90% and higher) in macrophage cultures of both groups and presumably, were presented by mainly epithelioid cells. The results indicated polarization of mononuclear and multinuclear macrophages in the M2 direction under conditions of BCG granulomatosis and a higher initial M2 polarization of binuclear macrophages. In control cultures, the ratio of M2 to M1 macrophages was 0.57, in experimental cultures this ratio was 1.6. It seems that long persistence of Mycobacterium tuberculosis in macrophages served as a factor stimulating the plastic processes and transformation of macrophages into epithelioid cells that form the "core" of granulomas and their enlargement upon incorporation of macrophages.