4061
PU.1 is expressed at high levels in B cells , mast cells , megakaryocytes , macrophages , neutrophils , and immature erythroid cells and at lower levels in mature erythrocytes .
 ( protein: PU.1, None) , ( cell type: B cells, None) , ( cell type: neutrophils, None) , ( cell type: mast cells, None) , ( cell type: macrophages, None) , ( cell type: immature erythroid cells, None) , ( cell type: megakaryocytes, None) , ( cell type: mature erythrocytes, 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: PU.1, None) , ( cell type: B cells, None) , ( cell type: neutrophils, None) , ( cell type: mast cells, None) , ( cell type: macrophages, None) , ( cell type: immature erythroid cells, None) , ( cell type: megakaryocytes, None) , ( cell type: mature erythrocytes, None) 