Monocytes are large immune cells that develop from monoblasts in the bone marrow. Monocytes populations circulate in the blood vessels and reside in other tissues. The reported half-life of circulating mouse monocytes is 17 hours. Tissue-residing monocytes differentiate into macrophages or dendritic cells. Mouse monocyte isolation kits and reagents are convenient tools for cell separation that utilize magnetic binding to key cell markers.