STAT3 and B-cell chronic lymphocytic leukemia: Taken as a whole, these results indicate that type I and II IFNs promote the resistance of CLL cells to apoptosis by activating Src and TYK2 (IFN-α/β) or Src and JAK2 (IFN-γ) tyrosine kinases respectively, which in turn activate the survival STAT3/Mcl-1 axis.