8648
To clarify the etiological relationship between the two variants, we analyzed responsiveness to IL-4 of transfectants with four kinds of IL-4Ralpha carrying either Val or Ile at 50 and either Gln or Arg at 551 .
 ( protein: IL-4, None) , ( protein: IL-4Ralpha, None) , ( protein: 551, None) , ( protein: 50, 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: IL-4, None) , ( protein: IL-4Ralpha, None) , ( protein: 551, None) , ( protein: 50, None) 