7237
In vivo, CD8+ T cells and, less frequently, CD4+ T cells may completely lose CD28 surface expression during chronic infections and with aging.
 ( cell type: CD4+ T cells, None) , ( cell type: CD8+ T cells, 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: CD4+ T cells, None) , ( cell type: CD8+ T cells, None) , ( protein: CD28, None) 