CCL2 and age-related macular degeneration: Significantly, the DKO model has earlier onset and higher penetrance than the two single knockout models of Ccl2 and Cx3cr1. DKO shows multiple small retinal lesions by 4–6 weeks of age, comparable to the focal retinal lesions in human AMD, in addition to RPE degeneration, A2E elevation, and aberrant complement deposition [8,18].