APOE and Alzheimer disease: As there is strong LD between DRB5*01 and DRB1*15:01~DQB1*06:02 [64], it is possible that the AD association we have detected with DR15 is due in part or wholly to DRB5. Finally, our finding that HLA associations with AD are stronger in APOE ɛ4-negative individuals is consistent with prior work for different HLA alleles [65,66].