Importantly, diabetic Cd40−/− mice are protected from retinal upregulation of intercellular adhesion molecule 1 (ICAM-1), TNF-α, IL-1β, nitric oxide synthase 2 (NOS2) and C-C motif chemokine ligand 2 (CCL2) and do not develop diabetic retinopathy [4, 5]. This evidence concerns the gene NOS2 and diabetic retinopathy.