8901
Previous studies have shown that binding to cell-surface heparan sulphate is essential for optimal activity of IFN-gamma and that free heparin competitively inhibits this sequestration process .
 IFN-gamma
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:
 IFN-gamma