1267
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.
 ( cell type: immature thymocytes, None) , ( cell type: childhood acute T lymphoblastic leukemia cells, None) , ( protein: CR2/CD21, None) , ( protein: EBV receptor, None) , ( cell type: T cells, None) , ( cell line: T lymphoblastoid cell lines, None) 
Locate the role in the text that participated in the event based on the event type and return it in the event list. 
 Option: Event type: RNA,cell type,protein,cell line,DNA, Arguments type: . 
Text: {0} 
Answer:
 ( cell type: immature thymocytes, None) , ( cell type: childhood acute T lymphoblastic leukemia cells, None) , ( protein: CR2/CD21, None) , ( protein: EBV receptor, None) , ( cell type: T cells, None) , ( cell line: T lymphoblastoid cell lines, None) 