13529
Using interspecies hybrids, the segregation of human chromosomes allowed us to establish that MHC class II extinction is linked to the presence in the hybrids of the chromosomes from the epithelial fusion partner .
 ( DNA: chromosomes, None) , ( protein: MHC class II, None) , ( DNA: human chromosomes, None) , ( cell type: epithelial fusion partner, 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:
 ( DNA: chromosomes, None) , ( protein: MHC class II, None) , ( DNA: human chromosomes, None) , ( cell type: epithelial fusion partner, None) 