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By contrast, memory cells, either in vitro activated helper T cells reverting to a resting state, or CD4+ T (memory) clones , or CD4+CD45RO+ T cells isolated ex vivo, no longer have a silencer .
 silencer, CD4+CD45RO+ T cells, CD4+ T (memory) clones, vitro activated helper T cells
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:
 silencer, CD4+CD45RO+ T cells, CD4+ T (memory) clones, vitro activated helper T cells