3902
Constitutive expression of specific interferon isotypes in peripheral blood leukocytes from normal individuals and in promonocytic U937 cells .
 promonocytic U937 cells, interferon isotypes, peripheral blood leukocytes
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:
 promonocytic U937 cells, interferon isotypes, peripheral blood leukocytes