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A segmental analysis of the key regions of HLA - DR1 that control T cell allorecognition was performed by using a series of transfected cell lines expressing the products of recombinant DRB / H - 2Eb genes , paired with either DR alpha or H - 2E alpha .
 HLA - DR1, DRB, H - 2Eb, DR alpha, H - 2E alpha
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: GENE 
Text: {0} 
Answer:
 HLA - DR1, DRB, H - 2Eb, DR alpha, H - 2E alpha