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Previous studies have characterized the CD28 augmentation of TCR -mediated signaling in peripheral blood T cells through transcriptional activation of an IL-2 promoter CD28 response element ( CD28RE ), along with enhanced mRNA stability.
 IL-2, TCR, peripheral blood T cells, CD28, CD28 response element, CD28RE, CD28
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:
 IL-2, TCR, peripheral blood T cells, CD28, CD28 response element, CD28RE, CD28