A. IFN signaling in A549 cells: 10-fold serial dilutions of recombinant B18R protein (1 to 100 ng/mL, final assay concentration) were prepared in media and combined with a constant amount (1 ng/mL, final assay concentration) of each IFN protein (sIFN-I or IFNα-2b) for 1 h at room temperature. The B18R/IFN complexes were transferred to cells and then incubated for 30 min. The phosphorylation and total signal of STAT1, STAT2, and STAT3 were detected by immunoblot and the p-STATs level were quantified compared to their corresponding total STAT proteins, +, means treatment with 100 ng/mL B18R protein.
B. IFN signaling in HeLa cells was analyzed as in Panel A.