tokens: TNF-alpha RNA was undetectable in U937 cells , whereas a low constitutive level was detected in U9-IIIB cells .
folded_tokens: tnf-alpha rna was undetectable in u937 cells , whereas a low constitutive level was detected in u9-iiib cells .
labels: B-protein_molecule O O O O B-cell_line I-cell_line O O O O O O O O O B-cell_line I-cell_line O