6586
Recent studies have suggested that the diversity of TCR repertoire after primary immunization is conserved in memory T cells and that a progressive narrowing of this repertoire may take place during recall infections .
 ( protein: TCR, None) , ( cell type: memory T 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: TCR, None) , ( cell type: memory T cells, None) 