CTLA4 and Alzheimer disease: Correlation analyses between the MMSE values and the investigated T cell populations ruled out a positive correlation with CD28 + CD8 + T cells (p = 0.0466) and a negative correlation with CTLA-4 + CD4 + (p = 0.0003) in severe AD, illustrating that the decline of MMSE is associated with a decrease in CD28 expressing CD8 + T cells and an increase in CTLA-positive CD4 + T cells (Table 3a).