3906
This endogenous IFN was also shown to play a role in maintaining the basal level of expression of the major histocompatibility class I genes in lymphoid cells .
 ( DNA: major histocompatibility class I genes, None) , ( cell type: lymphoid cells, None) , ( protein: endogenous IFN, 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: major histocompatibility class I genes, None) , ( cell type: lymphoid cells, None) , ( protein: endogenous IFN, None) 