Mouse models have been particularly valuable in this context: using the ApoE knockout/western-type diet model of atherosclerosis, early experiments revealed the importance of the chemokine receptor CCR2 in atherogenesis (98) and subsequently that the murine equivalent of the classical monocyte subset (Ly6Chi CCR2+ monocytes) migrates in response to the chemokine CCL2 (99, 100). The gene discussed is CCR2; the disease is atherosclerosis.