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 .
 PKR, HIV-1 -infected cells, anti-IFN-alpha/beta antibody, IFN, PKR
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: cell line, protein, RNA, DNA, cell type 
Text: {0} 
Answer:
 PKR, HIV-1 -infected cells, anti-IFN-alpha/beta antibody, IFN, PKR