In FTD patients, while one study described a decrease of total T cell percentages in blood samples (Busse et al., 2017), another study described a specific decrease of cytotoxic T lymphocyte antigen-4 (CTLA-4) CD4 T cells and no change of CD28 CD4 T cell frequency in patients’ blood (Santos et al., 2014). Here, CTLA4 is linked to frontotemporal dementia.