3905
Culture supernatants from uninduced U937 cells were also found to activate an ISRE cloned upstream of the luciferase reporter gene , indicating the presence of endogenous IFN activity equivalent to approximately 0.3 to 0.5 IU/mL.
 endogenous IFN, uninduced U937 cells, ISRE, luciferase, luciferase reporter gene
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:
 endogenous IFN, uninduced U937 cells, ISRE, luciferase, luciferase reporter gene