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Our studies thus indicate that, despite the rapidity of NK cell-mediated lysis , AP-1 transcription factor is activated during the early stage of NK cell cytolytic programs and that engagement of NK cell inhibitory receptors for MHC class I molecules impairs the very early activation of AP-1 .
 AP-1 transcription factor, NK cell inhibitory receptors, AP-1, MHC class I molecules
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:
 AP-1 transcription factor, NK cell inhibitory receptors, AP-1, MHC class I molecules