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RB -defective tumor lines are non-inducible for MHC class II by IFN-gamma , or very weakly inducible, but transfection of 2 different lines with RB expression vectors re-establishes or substantially enhances class II inducibility .
 RB expression vectors, RB, IFN-gamma, RB -defective tumor lines, RB, MHC class II
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:
 RB expression vectors, RB, IFN-gamma, RB -defective tumor lines, RB, MHC class II