1492
A mechanism is suggested whereby expression of c-jun and junB , in the absence of members of the fos family , can prevent inappropriate activation of T cells caused by ligation of CD28 in the absence of a specific antigenic stimulus .
 ( cell type: T cells, None) , ( DNA: c-jun, None) , ( DNA: fos family, None) , ( protein: CD28, None) , ( DNA: junB, 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: T cells, None) , ( DNA: c-jun, None) , ( DNA: fos family, None) , ( protein: CD28, None) , ( DNA: junB, None) 