2667
We have examined the effects of RA on normal hematopoiesis by using early hematopoietic progenitor cells ( HPC ) stringently purified from adult peripheral blood .
 ( cell type: HPC, None) , ( cell type: hematopoietic progenitor 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: HPC, None) , ( cell type: hematopoietic progenitor cells, None) 