AIF1 and neurodegenerative disease: Because a switch in the activation status of microglia has been described in experimentally-induced stress and in animal models of neurodegenerative diseases (Streit, 2005), we next evaluated microglia localization and the status of activation in the retinas of old Igf1+/+ and Igf1−/− mice by performing double Cd11b and Iba-1 immunostaining.