Featured ArticleMethylation profiles in peripheral blood CD4+ lymphocytes versus brain: The relation to Alzheimer's disease pathology

IntroductionWe investigated the change in DNA methylation in peripheral blood CD4+ lymphocytes over time, examined the relation between CD4+ lymphocytes and brain methylation, and compared their associations with AD pathology.MethodsGenome-wide methylation was measured three times in 41 older persons using Illumina Infinium HumanMethylation450 array. The two CD4+ lymphocytes measures were at study baseline and proximate to death. Brain tissue came from frozen dorsolateral prefrontal cortex.ResultsGlobal methylation features were conserved across tissue. At individual CpG sites, methylation level was concordant between the two CD4+ lymphocytes but more diffuse between CD4+ lymphocytes and brain. Previous associations of brain methylation with neuritic plaques at target methylation sites were not replicated in CD4+ lymphocytes.DiscussionThere is no strong evidence of change in CD4+ lymphocytes methylation among older persons over an average of 7.5 years. Methylation associations with AD pathology found in neocortex are not directly reflected in CD4+ lymphocytes.