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 .
 PU.1, B cells, neutrophils, mast cells, macrophages, immature erythroid cells, megakaryocytes, mature erythrocytes
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: cell line, protein, RNA, DNA, cell type 
Text: {0} 
Answer:
 PU.1, B cells, neutrophils, mast cells, macrophages, immature erythroid cells, megakaryocytes, mature erythrocytes