CCL5 and retinal degeneration: Therefore, we hypothesise that the additional neurotoxic effect of Cx3cr1 deficiency on the retinal degeneration caused by the Crb1RD8/RD8 mutation might be due to an impaired migratory capability and a subsequent reduced removal of dying photoreceptors by Cx3cr1-deficient microglia which might result in the production of more neurotoxic inflammatory mediators including Ccl5, TNFa or IL-6, which may negatively affect photoreceptor cell survival, and have all been previously shown to be upregulated in CCDKO mice [28], [30], [42], [60], [61].