Since it is well documented that infection and inflammation are common in elderly individuals, and preclinical studies have reported that inflammation induced AD pathologic characteristics in mice who only carried ApoE4,16,17 our findings may explain why ApoE4 carriers have increased risk for AD at an old age and suggest that treating chronic low-grade inflammation may delay the onset of AD in ApoE4 carriers. This evidence concerns the gene APOE and Alzheimer disease.