Characterization of bone marrow GM-CSF-derived dendritic cells and their response to M. bovis BCG.

Dendritic cells (DCs) play a crucial role in initiating and orchestrating the immune response through cytokine secretion and co-stimulatory molecule expression. Mycobacteria employ various escape mechanisms, such as altering host cell response and metabolism. DCs are an important bacterial reservoir Mycobacterium tuberculosis infection. During infection, DCs exhibit reduced antigen presentation capability and ability to induce a protective response. Several differentiation protocols for DCs derived from mouse bone marrow (BMDC) progenitors have been reported in the literature. However, these protocols remain controversial regarding DC differentiation rates and the influence of specific conditions used in each model. In order to support data obtained with BMDCs, it is important to characterize these cells according to activation parameters and responses to mycobacterial infection. Therefore, this study aims to characterize the differentiation protocol of DCs derived from C57BL/6 mouse bone marrow and their response to M. bovis BCG infection (CEUA/UFF #1454031119). We demonstrated that GM-CSF (10ng/ml) leads to 70% CD11c+ cells in 7 days and 95% in 10 days among the semi-adherent cell population. We evaluated MHCII and CD80 expression on cells in suspension (SC), semi-adherent cells (SAC) and adherent cells (AC). We observed that SC presented higher expression of MHCII and CD80 on CD11c+, when compared to the other cell populations. However, SAC presented a meaningful percentage of CD11c+ MHCII high CD80+ cells (66%) compared to AC (47%). Indeed, at 14 days CD11c+ cells in SC and SAC populations express high levels of MHCII and CD80 and lower levels of F4/80 compared to AC. Our data suggests that different populations are differentiated from mouse bone marrow in the presence of GM-CSF. Further investigation should be done to better charactherize these populations and how they respond to mycobacterial infection.