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In addition, we show that TNF-alpha is a potent costimulatory factor of the very immature CD34+Thy-1+ CB subset .
 TNF-alpha, immature CD34+Thy-1+ CB subset
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:
 TNF-alpha, immature CD34+Thy-1+ CB subset