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We have purified these activities and found that the principal IL-2 -inducible component bears significant relatedness to a prolactin-induced transcription factor first identified in sheep mammary gland tissue .
 ( protein: prolactin-induced transcription factor, None) , ( cell type: sheep mammary gland tissue, None) , ( protein: IL-2, None) , ( protein: IL-2 -inducible component, 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: prolactin-induced transcription factor, None) , ( cell type: sheep mammary gland tissue, None) , ( protein: IL-2, None) , ( protein: IL-2 -inducible component, None) 