6100
Studies with motheaten mice , which lack the SHP1 protein tyrosine phosphatase , indicate that this enzyme plays an important negative role in T cell antigen receptor ( TCR ) signaling .
 SHP1, tyrosine phosphatase, T cell antigen receptor, SHP1 protein, TCR
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:
 SHP1, tyrosine phosphatase, T cell antigen receptor, SHP1 protein, TCR