A higher ratio of CD4+/CD8+ T cells was found in the in peripheral blood of AD patients and AD mouse models compared to relevant controls, concomitant with lower CD8+ T‐cell counts and lower total CD3 expression (Hu et al., 1995; Pirttila et al., 1992; Schindowski et al., 2007; Shalit et al., 1995; St‐Amour et al., 2014, 2019). This evidence concerns the gene CD4 and Alzheimer disease.