3226
In germinal centers GC , p50 , p52 , and RelB were found in the nuclei of FDC only and were not detected in the nuclei of CD68+ cells .
 ( cell type: FDC, None) , ( protein: p52, None) , ( protein: p50, None) , ( protein: RelB, None) , ( cell line: CD68+ 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:
 ( cell type: FDC, None) , ( protein: p52, None) , ( protein: p50, None) , ( protein: RelB, None) , ( cell line: CD68+ cells, None) 