PTGDR2 and Alzheimer disease: There was no significant difference in the level of CD4+CCR6+CRTh2+ cells between the AR group and the non-AR group(1.3 %±0.6 and 1.2 %±0.8 %) (p > 0.05), as well as between the AD group and the non-AD group(1.2 %±0.8 and 1.3 %±0.8 %) (P > 0.05, Fig. 1).