In neurodegenerative diseases, Chuang et al. unveiled five significant CpGs.42 Elaheh et al. observed allele-specific methylation in CD4+ cells instead of saliva.43 In autoimmune diseases, altered DNA methylation profiles appear to be present in saliva in Coeliac disease individuals.44 Biomarker research boom in neurodegenerative diseases might be due to the difficulty in the obtaining of the brain for biopsy. This evidence concerns the gene CD4 and neurodegenerative disease.