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Using tetanus toxoid specific and HLA-DR-restricted T lymphocytes , we show that polarized intestinal epithelial cells directed to express HLA-DR molecules are able to initiate class II processing only after internalization of antigen from their apical surface.
 polarized intestinal epithelial cells, HLA-DR molecules
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:
 polarized intestinal epithelial cells, HLA-DR molecules