PB or CSF of AD patients: decreased proportion (Shalit et al., 1995; Speciale et al., 2007; Larbi et al., 2009); no difference (McKinney et al., 2021); increased number (Schindowski et al., 2007; Gate et al., 2020; Heneka, 2020); increased number of effector/memory CD8+ T cells (Heneka, 2020). Brain tissue of AD patients: present in the brain (Itagaki et al., 1988; Merlini et al., 2018; Hobson and Sulzer, 2022). Mice model: accumulated in the mouse brain (Laurent et al., 2017; Merlini et al., 2018; Unger et al., 2020; Michael et al., 2021). Here, CD8A is linked to Alzheimer disease.