1271
However, during infection by EBV , ligation of CD2 caused thymocytes to proliferate in the absence of exogenous cytokines .
 ( cell type: thymocytes, None) , ( protein: CD2, None) , ( protein: exogenous cytokines, 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: thymocytes, None) , ( protein: CD2, None) , ( protein: exogenous cytokines, None) 