In agreement with a pathogenic role for classical monocytes and homeostatic role of non-classical monocytes in the eye, Ccr2−/− and Ccl2−/− mice are resistant to diabetic retinopathy [22, 23], while Cx3cr1−/− and Nr4a1−/− mice, two models of non-classical monocyte deficiency, show exacerbated diabetic retinopathy progression [24, 25]. This evidence concerns the gene CCL2 and diabetic retinopathy.