The partial Jak2-FF signaling is biological relevant. (A) Jak2^+/+, Jak2^FF/FF, and Jak2^−/− MEFs were stimulated with IFN-γ for the indicated time points. Subsequently, cellular lysates and protein extracts were prepared and analyzed by immunoblotting. One representative experiment out of 3 independent experiments is shown. The asterisk indicates a nonspecific band detected by the IRF1 antibody. (B) Jak2^+/+, Jak2^FF/FF, and Jak2^−/− MEFs were stimulated with IFN-γ for the indicated time points or left untreated. As a readout for IFN-γ signaling, MHC-I (H-2K^b) surface expression was measured via flow cytometry. One representative experiment of 3 independent experiments run in triplicate is shown. The standard deviation is indicated for each data point. ***P < .001, **P < .01. (C) Jak2^−/− MEFs were transiently transfected with Jak2-wt, Jak2-FF, Jak2-ΔJH1, Jak2-ΔJH1+2, and a GFP expression plasmid construct. Then 24 hours postcotransfection, GFP-positive and GFP-negative cells were analyzed via flow cytometry for MHC-I surface expression. One representative experiment of 3 independent experiments run in triplicate is shown. The standard deviation is indicated for each data point. ***P < .001. (D) Jak2^+/+, Jak2^FF/FF, and Jak2^−/− MEFs were either mock treated or incubated with 500 IU/mL IFN-γ for 48 hours before infection with VACV Western Reserve at 0.05 PFU/cell. VACV progeny titers were determined at 48 hours postinfection by plaque assay on CV-1 cells. One representative experiment of 3 independent experiments is shown. Each data point represents the arithmetic mean of 4 duplicate samples titrated at least in duplicate (n = 4 × 2). The standard deviation is indicated for each data point. ***P < .001.