CR1 and Alzheimer disease: Of note, mice do not express CR1 but mice that lack the murine ortholog Cr1-related protein Y (Crry) show reduced inflammatory responses and attenuated increases in AD-related disease progress biomarkers (Killick et al., 2013), further suggesting that activation of the complement system is a key feature of the aging hippocampus that also plays a role in AD pathogenesis.