CD4 and Alzheimer disease: Specifically, HB treatment reduced the frequency of CD4+ T cells that were substantially reduced in the DNCB-induced AD mouse model group (Figure 3B), while no difference was observed in the frequencies of CD8+ T cells (Figure 3C), which led to an increased CD4/CD8 ratio in the DNCB-induced AD mouse model group after HB treatment (Figure 3D).