7242
CD4+ and CD8+ T cells differ in their beta-binding profiles , which may explain the more pronounced down-regulation of CD28 in senescent CD8+ T cells .
 CD28, CD8+ T cells, CD8+ 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:
 CD28, CD8+ T cells, CD8+ T cells