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The CD4 coreceptor interacts with non-polymorphic regions of major histocompatibility complex class II molecules on antigen-presenting cells and contributes to T cell activation .
 CD4 coreceptor, non-polymorphic regions, antigen-presenting cells, major histocompatibility complex class II 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:
 CD4 coreceptor, non-polymorphic regions, antigen-presenting cells, major histocompatibility complex class II molecules