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Previous work has shown that C/EBP sites and C/EBP transcriptional activators are necessary for HIV-1 LTR activity in monocytes/macrophages .
 C/EBP sites, HIV-1 LTR, monocytes/macrophages, C/EBP transcriptional activators
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:
 C/EBP sites, HIV-1 LTR, monocytes/macrophages, C/EBP transcriptional activators