3686
Constitutive PKR activity was also detected in HIV-1 -infected cells as a result of low-level IFN production , since the addition of anti-IFN-alpha/beta antibody to the cells decreased PKR expression .
 ( protein: PKR, None) , ( cell line: HIV-1 -infected cells, None) , ( protein: anti-IFN-alpha/beta antibody, None) , ( protein: IFN, None) , ( protein: PKR, None) 
Locate the role in the text that participated in the event based on the event type and return it in the event list. 
 Option: Event type: RNA,cell type,protein,cell line,DNA, Arguments type: . 
Text: {0} 
Answer:
 ( protein: PKR, None) , ( cell line: HIV-1 -infected cells, None) , ( protein: anti-IFN-alpha/beta antibody, None) , ( protein: IFN, None) , ( protein: PKR, None) 