Biochemical and immunological phenotype alterations in human monoblastoid cell line U-937 induced by physiological (interferon-alpha, retinoic acid) and nonphysiological (phorbol ester) inducers.

Human monoblastoid cell line U-937 was induced by recombinant or leukocyte human interferon-alpha, retinoic acid, by their combination, or by 12-0-tetradecanoyl-phorbol-13-acetate (TPA), to express some differentiation-associated markers and characteristics. Induced biochemical alterations were studied with the aid of two-dimensional electrophoretic analysis (isoelectrofocusing/SDS-PAGE) of 125I-lactoperoxidase radioiodinated cell surface proteins, 35S-methionine metabolically radiolabeled cell proteins and 32P orthophosphate radiolabeled cell phosphoproteins. Alteration of immunophenotype markers was studied by continuous flow immunocytofluorometry with a panel of monoclonal antibodies directed to leukocyte antigens, cell proliferation, DNA, RNA, and protein synthesis by radioactive precursor incorporation techniques. Furthermore, cytochemical markers, cell adherence and nitroblue tetrazolium (NBT) reduction were utilized to follow the induction of differentiation-associated characteristics. Differential alterations of some immunophenotype markers induced by diverse inducers were observed. Major induced alterations included down-regulation of CD4 (induced by TPA, and to a lesser extent by IFN-alpha), TPA-induced decrease of cell surface expression of transferrin receptor (unmodified by IFN-alpha) and IFN-alpha induced increase of antigen density (fluorescence intensity) of MHC class I antigen. Marked retinoic acid and interferon-alpha induced increase in membrane expression of antigen(s) detected by monoclonal antibodies BraC6 and BraC8, elicited with healthy donor's granulocytes, was also observed.