ApoE isoform-dependent immunomodulatory activities: In humans, there are three major alleles of the apolipoprotein E (APOE) gene, which are APOE2, APOE3, and APOE4. APOE4 is the strongest genetic risk factor for late-onset forms of Alzheimer’s disease, which may be due to a number of distinct functions of ApoE4 protein versus the more prevalent ApoE3 protein. This evidence concerns the gene APOE and Alzheimer disease.