4228
The data further indicate that the IL-7R alpha chains are directly involved in the activation of JAKs and STATs and have a major role in proliferative signaling in precursor B cells .
 protein: JAKs; protein: STATs; protein: IL-7R alpha chains; cell type: precursor B cells
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: JAKs, STATs, IL-7R alpha chains, precursor B cells 
Answer:
 protein: JAKs; protein: STATs; protein: IL-7R alpha chains; cell type: precursor B cells