Theclass of apolipoprotein E (ApoE) proteins plays a major role in regulatingintestinal immune system homeostasis, colonic inflammation and composition ofthe microbiota, and therefore it is tempting to speculate that APOE ε4 allele status could be associated withpathological changes in all these parameters; however, it must be stressed thatthere is no evidence regarding this area in AD or indeed any other disease[118]. Here, APOE is linked to Alzheimer disease.