At the baseline, the value of pDCs' CD4 MFI was 21.18±1.93, which was significantly decreased at days 3 (16.77±2.83, P = 0.039), 6 (16.05±3.29, P = 0.049), 15 (11.37±1.59, P = 0.05), 19 (12.06±2.18, P = 0.002), 27 (14.55±1.89, P = 0.001), 34 (15.58±0.96, P = 0.01), and 62 (12.34±3.05, P = 0.028) p.i. This indicates that the SIVmac239 infection downregulated the expression of CD4 on pDCs. The gene discussed is CD4; the disease is infection.