3902
Constitutive expression of specific interferon isotypes in peripheral blood leukocytes from normal individuals and in promonocytic U937 cells .
 ( cell line: promonocytic U937 cells, None) , ( protein: interferon isotypes, None) , ( cell type: peripheral blood leukocytes, 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:
 ( cell line: promonocytic U937 cells, None) , ( protein: interferon isotypes, None) , ( cell type: peripheral blood leukocytes, None) 