Dependent on which and how severely each of the chemokine pathways are affected by endogenous genetic variants within this cellular signalling network, the responses of recruited microglia or monocytes will differ and can either exacerbate retinal degeneration, as observed for Cx3cr1 deficient mice in combination with the Crb1RD8/RD8 mutation, or may act mildly protective as eventually indicated by the trend towards a slight reduction in lesion size in Ccl2 deficient mice which also carry the Crb1RD8/RD8 mutation. This evidence concerns the gene CCL2 and retinal degeneration.