In addition to these effects, APOE-ε4 decreases plasma interleukin 7 (IL-7) levels and interleukin 7 receptor (IL-7R) signaling in in peripheral blood mononuclear cells, disrupting immune balance and enriching T cells, which may exacerbate neuroinflammation, hippocampal atrophy, and neuronal damage [20]. Here, IL7 is linked to Atrophy.