IFN-α Secretion by Type 2 Predendritic Cells Up-Regulates MHC Class I in the HIV-1-Infected Thymus

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Abstract
The ability of HIV-1 to evade the host immune response leads to the establishment of chronic infection. HIV-1 has been reported to up-regulate MHC I molecules on the surface of thymocytes from HIV-1-infected thymus. We demonstrate in this study that HIV-1 up-regulates MHC I on both HIV-1-infected and uninfected thymocytes in a manner that is independent of Nef, proportional to viral replication, and entirely mediated by IFN-α. IL-3Rα+ type 2 predendritic cells (preDC2) resident in the thymic medulla secrete IFN-α, which acts on IFN-αβR-expressing immature thymocytes to induce MHC I expression. Furthermore, thymic preDC2 are permissive for HIV-1 infection and positive for intracellular p24. These data demonstrate the ability of IFN-α secreted by preDC2 to induce MHC I up-regulation in the HIV-1-infected human thymus.