11957
The tumour associated cell surface antigen A6H is costimulatory for human CD4+ but not CD8+ T cells .
 ( protein: A6H, None) , ( protein: tumour associated cell surface antigen, 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: A6H, None) , ( protein: tumour associated cell surface antigen, None) 