Harvest mouse bone marrow cells from femurs using a syringe and needle with 5 ml 1x DPBS. 2. Centrifuge the cell suspension at 200 x g at room temperature for 5 min. 3. Remove the supernatant and suspend the cell pellet with 2 ml ACK lysing buffer for 1 min to deplete red blood cells. If red blood cells are not completely depleted, repeat the ACK lysing buffer step until they are. 4. Filter the cell suspension through a 40 μm nylon strainer. 5. Wash the strainer with 2 ml 1x DPBS and centrifuge at 200 x g at room temperature for 5 min. 6. Wash the cell pellet with 1x DPBS and re-suspend in 15 ml complete DMEM medium with 20 ng/ml murine M-CSF in a 100 mm Petri dish. 7. Incubate at 37 °C, 5% CO2. 8. After 3 days, replace half of the medium with fresh complete DMEM medium. Repeat this step every 2 days. 9. On Day 4, cells containing more than 80% CD11b+/F4/80+ macrophages are ready for further experiments.