1486
The T cell surface molecule CD28 binds to ligands on accessory cells and APCs , playing an important costimulatory role in the response of T cells to Ags .
 ( protein: T cell surface molecule, None) , ( protein: CD28, None) , ( cell type: T cells, None) , ( cell type: APCs, None) , ( protein: Ags, None) , ( cell type: accessory cells, 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: T cell surface molecule, None) , ( protein: CD28, None) , ( cell type: T cells, None) , ( cell type: APCs, None) , ( protein: Ags, None) , ( cell type: accessory cells, None) 