Comparisons of initial tyrosine phosphorylation of STAT proteins induced by IFN-α in sensitive (D_W^S) and resistant (D_W^R) Daudi cells. At 15 minutes after identical treatment with IFN-α2a (100 U/mL), cells were extracted for concordant immunoprecipitation (IP) with specific STAT antibodies, gel electrophoresis, and Western blot. Patterns of the STAT-pTyr are shown with 4G10 blots developed by ECL. Total latent and phosphorylated STAT proteins were assessed by reprobing of transfer membranes with specific anti-STAT antibodies and secondary detection by ECL.