Macrophage and dendritic cell precursors (MDP) in the bone marrow give rise to Ly6Chi monocytes or inflammatory monocytes, which exit the bone marrow in a CC-chemokine receptor 2 (CCR2)- dependent manner in response to infection to the inflamed tissues (Serbina et al., 2008; Geissmann et al., 2010). This evidence concerns the gene CCR2 and infection.