1735
The inhibitory effect exerted by anti- CD28 was observed at the level of DNA binding as well as in functional reporter-gene assays .
 ( protein: CD28, None) , ( protein: anti- 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: CD28, None) , ( protein: anti- CD28, None) 