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 .
 major histocompatibility class I genes, lymphoid cells, endogenous IFN
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:
 major histocompatibility class I genes, lymphoid cells, endogenous IFN