HIV-1 infection induces pDC activation in DKO-hu mice. (A) Elevated IFNα in HIV-1–infected DKO-hu mice. Plasma from mock or HIV-1–infected mice at 1 week after infection was analyzed for IFNα with the Human Cytokine Luminex kit. IFNα in the mock-infected plasma was lower than the detection limit (< 13 pg/mL). SD is shown as error bar (n = 7 mice). (B) HIV-1 infection activated pDCs in the BM in vivo. BDCA2⁺CD123⁺ pDCs from BM of mock or HIV-infected mice were analyzed for HLA-DR expression by FACS. The number indicates the mean fluorescence intensity (MFI) of total pDCs. Shaded plots are IgG isotype controls. (C) Summarized data show relative expression of HLA-DR on pDCs from BM, spleen (SP), or mesenteric lymph node (mLN) cells. Error bars indicate SDs. pDCs from mock or HIV-infected mice were analyzed for CD38 (D), ICOS-L (E), or CD80 (F) expression. The number is MFI of total pDCs. Shown is summarized data from 3 mock and 4 HIV-infected DKO-hu mice at 2 weeks after HIV infection. P values between mock and HIV-infected groups were calculated by nonparametric Student t test. *P < .05, **P < .01, (G) pDC activation is correlated with CD4⁺ T-cell activation and apoptosis. BM cells from 3 mock (▿) and 6 HIV-infected (●) mice were analyzed. Cells were stained with surface markers, followed by caspase3 intracellular staining. CD123⁺BDCA2⁺ pDCs and CD3⁺CD4⁺ T cells from BM were analyzed for caspase3 or HLA-DR expression. Correlations were analyzed with the Spearman nonparametric test; squared correlation coefficients (R²), and P values were shown.