4550
Therefore, as T cells progress from primary TCR activation through IL-2 -dependent proliferation, followed by secondary TCR stimulation , their responsiveness to IFN-gamma varies, and this may affect their ability to participate in an ongoing immune response .
 IL-2, TCR, T cells, IFN-gamma, TCR
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, T cells, IFN-gamma, TCR