13869
Thus, human erythroid precursors can be expanded in vitro in sufficient numbers and purity to allow its usage in signal transduction studies .
 cell type: human erythroid precursors
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: cell line, protein, RNA, DNA, cell type 
Text: {0} 
 Entities: human erythroid precursors 
Answer:
 cell type: human erythroid precursors