Figure 2

Type I interferon signaling is required for the induction of the retinoid anti-MuV response. U937 cells were infected with MuV at an MOI of 0.01 and treated with 1 μM ATRA or DMSO. 48 hr post-infection, RNA was extracted and analyzed for IFNα1 (A), IFNβ (C), IRF-1 (E) and RIG-I (F) expression by qPCR. Supernatants were analyzed by ELISA for IFNα1 (B) or IFNβ (D) protein. (G) U937 cells were treated with increasing doses of ATRA (0-1000nM) and either mock infected or infected with MuV at an MOI 0.01. Protein was isolated from whole cell extracts and analyzed by western blot for phospho-STAT1 (Y701), total STAT1 or β-actin. (H) U937 cells were infected with MuV at an MOI of 0.01 and treated with 1 μM ATRA or DMSO and isotype control antibody or IFNAR2 antibody. 24 hr post-infection RNA was extracted and analyzed for RIG-I expression by qPCR. Data presented reflect three experiments performed in triplicate (N = 3). *p < 0.05, **p < 0.01, ***p < 0.001.