12991
Upon activation by antigens , helper T cells differentiate into one of several subsets, characterized by their distinct cytokine -production patterns .
 cytokine, antigens, helper T cells
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:
 cytokine, antigens, helper T cells