tokens: In vivo , CD8+ T cells and , less frequently , CD4+ T cells may completely lose CD28 surface expression during chronic infections and with aging .
folded_tokens: in vivo , cd8+ t cells and , less frequently , cd4+ t cells may completely lose cd28 surface expression during chronic infections and with aging .
labels: O O O B-cell_type I-cell_type I-cell_type O O O O O B-cell_type I-cell_type I-cell_type O O O B-protein_molecule O O O B-other_name I-other_name O O O O