5745
In many circumstances it is difficult to distinguish the effects of CD28 from subsequent actions of cytokines , such as IL-2 , on T cell proliferation .
 ( protein: IL-2, None) , ( protein: cytokines, None) , ( protein: CD28, 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-2, None) , ( protein: cytokines, None) , ( protein: CD28, None) 