tokens: Mononuclear leukocytes from young or elderly persons were sham-exposed or exposed to influenza virus for 1 , 24 , and 72 h .
folded_tokens: mononuclear leukocytes from young or elderly persons were sham-exposed or exposed to influenza virus for 1 , 24 , and 72 h .
labels: B-cell_type I-cell_type O O O O O O O O O O B-virus I-virus O O O O O O O O O