4152
To overcome this problem, we have exploited the observation that activated human T cell blasts can be stimulated via the CD28 surface molecule in the absence of antigenic challenge ; thus, we have been able to observe the response of normal T cells to CD28 activation in isolation.
 ( cell type: normal T cells, None) , ( cell type: human T cell blasts, None) , ( protein: CD28 surface molecule, None) , ( protein: CD28, 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:
 ( cell type: normal T cells, None) , ( cell type: human T cell blasts, None) , ( protein: CD28 surface molecule, None) , ( protein: CD28, None) , ( protein: CD28, None) 