sentences:  and negative feedback mechanisms
  
  Responsiveness to type I IFNs requires the expression of signaling components within a given target cell, including IFNAR and STATs.Expression levels and post-translational modifications to IFNAR and STATs can modify cell responsiveness.Importantly, signaling is impacted by different STAT protein expression levels and activation of STAT heterodimers and STAT homodimers; reducing STAT expression levels alters antiviral, antiproliferative and inflammatory responses to type I IFNs.