tokens: In vitro , human B lymphocytes undergo long-term proliferation when activated through CD40 , a protein expressed on their cell surface .
folded_tokens: in vitro , human b lymphocytes undergo long-term proliferation when activated through cd40 , a protein expressed on their cell surface .
labels: O O O B-cell_type I-cell_type I-cell_type O B-other_name I-other_name O O O B-protein_molecule O O O O O O O O O