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One of the most important cytokines involved in immune response regulation is interleukin 2 (IL-2), a potent activator of the proliferation and function of T lymphocytes and natural killer cells .
 cell type: natural killer cells; cell type: T lymphocytes; cell type: lymphocytes; protein: cytokines
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: cell line, protein, RNA, DNA, cell type 
Text: {0} 
Answer:
 cell type: natural killer cells; cell type: T lymphocytes; cell type: lymphocytes; protein: cytokines