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The discovery of EBV in certain T cell malignancies and the expression of the EBV receptor , CR2/CD21 , on a population of immature thymocytes , T lymphoblastoid cell lines , and childhood acute T lymphoblastic leukemia cells suggested that EBV -receptor interactions on T cells may be of importance.
 immature thymocytes, childhood acute T lymphoblastic leukemia cells, CR2/CD21, EBV receptor, T cells, T lymphoblastoid cell lines
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:
 immature thymocytes, childhood acute T lymphoblastic leukemia cells, CR2/CD21, EBV receptor, T cells, T lymphoblastoid cell lines