PDCD1LG2 and Alzheimer disease: Therefore, we compared the number of T-cell subsets and the expression of PD-1/PD-L1/PD-L2 in patients with mild AD (CDR = 1, age range: 71–88 years) and age-matched patients with moderate AD (CDR = 2, age range: 69–88 years) (Fig. 3A-C, Table 2, Additional file 1: Figure 1B).