6850
The immunoregulatory properties of hematopoietic stem cells ( HSCs ) have been recognized for more than 60 years , beginning in 1945 , when Owen reported that genetically disparate freemartin cattle sharing a common placenta were red blood cell chimeras .
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Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
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