Bone marrow cells were isolated by flushing the femur and tibia of 8-week-old male C57BL/6 mice. The isolated bone marrow cells were incubated with macrophage colony-stimulating factor (M-CSF; Peprotech, Cranbury, NJ, USA), and were differentiated (7 days) into BMDMs. Bone marrow cells were incubated in RPMI medium containing 30 ng/ml M-CSF, 10% fetal bovine serum (FBS), 1% penicillin/streptomycin, and 25 mM HEPES. The media were changed every 3 days.