Tyrosine phosphorylation of STAT1 and STAT3 was detected using commercial available kits (Cell Signaling Technology, Beverly, MA, USA) according to the manufacturer's instructions. Briefly, the membrane was incubated with the antibodies (rabbit IgG) anti-STAT1 antibody, anti-phosphorylated tyrosine 701 of STAT1 antibody, anti-STAT3 antibody, and anti-phosphorylated tyrosine 705 of STAT3 antibody, diluted as recommended at 1/2000 with Tris-buffered saline with 0.1% Tween 20 with 5% BSA. Antibody binding was detected by horseradish peroxidase-conjugated anti-rabbit IgG antibody diluted at 1/4000 with Tris-buffered saline with 0.1% Tween 20 with 5% BSA, and was revealed using the chemiluminescence system. Protein bands were quantified by densitometry using NIH-Image analysis, and STAT phosphorylation was compared with the total amount of STAT protein. IFN-γ-stimulated Hela cells were used as a positive control for STAT1 phosophorylation.