5530
We have focused on the study of the signal transduction pathways triggered by CD23 in human monocytes and the promonocytic cell line U937 .
 human monocytes, promonocytic cell line U937, CD23
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:
 human monocytes, promonocytic cell line U937, CD23