6620
One of the best understood apoptotic pathways occurs in T lymphocytes and is mediated by Fas /Fas ligand ( FasL ) interaction .
 ( protein: Fas, None) , ( cell type: T lymphocytes, None) , ( protein: FasL, None) , ( protein: /Fas ligand, 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:
 ( protein: Fas, None) , ( cell type: T lymphocytes, None) , ( protein: FasL, None) , ( protein: /Fas ligand, None) 