title: TNF-alpha inhibits anti-IgM-mediated apoptosis in Ramos cells.
abstract: We have examined the effects of tumor necrosis factor-alpha (TNF-alpha) as an inducer or modulator of necrosis and/or apoptosis in B cell lines. TNF-alpha does not induce either necrosis or apoptosis in EBV-positive or -negative cell lines, regardless of the culture conditions of the cells or the presence or absence of cytokines. By contrast anti-IgM induces apoptosis in two EBV-negative cell lines (Ramos and ST486) but not in EBV-positive cell lines. Since TNF receptor and CD40 belong to the TNF receptor superfamily and anti-CD40 is a known inhibitor of apoptosis, we tested for TNF-alpha's effects on the inhibition of apoptosis induced by anti-IgM. Our results indicate that TNF-alpha inhibits apoptosis induced by anti-IgM in Ramos cells but not in ST486. The effects are dose and time dependent; the degree of apoptosis achieved and the selectivity of the effect among cell lines are strikingly similar for both TNF-alpha and anti-CD40. Furthermore when both agents are tested together no additivity in the inhibition is observed. The inhibition of apoptosis is a direct effect of TNF-alpha and not a permissive effect of another cytokine, since it is observed in defined medium. Although anti-IgM induces both TNF-alpha secretion and TNF receptors in Ramos cells, the concentration of secreted TNF-alpha is too low to affect apoptosis. Inhibition does not involve perturbation of the cell cycle distribution of Ramos cells. Furthermore rapid induction of c-fos and the decrease in c-myc observed after anti-IgM treatment are both unaltered by TNF-alpha. Our results suggest that TNF-alpha is an inhibitor of apoptosis in Ramos cells, that its overall pattern of inhibition is similar to that of anti-CD40, and that both agents act at some point distal to the alteration of c-fos and c-myc by anti-IgM.
authors.affiliation: Regional Research Laboratory, Kaiser Foundation Hospitals, 1515 N. Vermont Avenue, Los Angeles, California, 90027, USA.
authors.forename: E
authors.initials: E
authors.lastname: Park
authors.forename: C I
authors.initials: CI
authors.lastname: Kalunta
authors.forename: T T
authors.initials: TT
authors.lastname: Nguyen
authors.forename: C L
authors.initials: CL
authors.lastname: Wang
authors.forename: F S
authors.initials: FS
authors.lastname: Chen
authors.forename: C K
authors.initials: CK
authors.lastname: Lin
authors.forename: J S
authors.initials: JS
authors.lastname: Kaptein
authors.forename: P M
authors.initials: PM
authors.lastname: Lad
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D001402:B-Lymphocytes / Q000166:cytology / Q000187:drug effects*; D001667:Binding, Competitive / Q000502:physiology; D002051:Burkitt Lymphoma; D019013:CD40 Antigens / Q000187:drug effects; D002453:Cell Cycle / Q000187:drug effects; D003470:Culture Media; D005069:Evaluation Studies as Topic; D005434:Flow Cytometry; D016762:Genes, fos / Q000187:drug effects; D016259:Genes, myc / Q000187:drug effects; D006801:Humans; D007075:Immunoglobulin M / Q000187:drug effects*; D009857:Oncogenes / Q000187:drug effects; D014407:Tumor Cells, Cultured / Q000166:cytology / Q000187:drug effects; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
chemical_list: D019013:CD40 Antigens; D003470:Culture Media; D007075:Immunoglobulin M; D014409:Tumor Necrosis Factor-alpha