title: TNF induction of EL4 hyposensitivity to lysis by recombinant (soluble) and membrane-associated TNFs: TNF binding, internalization, and degradation.
abstract: EL4 mouse thymoma cells sensitive to TNF-mediated lysis only in the presence of cycloheximide (S-EL4) or in the presence or absence of cycloheximide (N-EL4) were used in these experiments. Murine tumor cell line (S-EL4) sensitivity to TNF cytotoxicity is augmented when cycloheximide is added together with TNF or when cycloheximide is added 1 hr before or after TNF. No enhanced sensitivity is observed when target cells are incubated with cycloheximide 2-4 hr before or after the addition of TNF. In the absence of cycloheximide, S-EL4 cells preexposed to murine TNF are less susceptible to lysis by TNF and TNF receptor-conjugated TNF but are lysed by integral membrane TNF. TNF-induced hyposensitivity is partially reversed by actinomycin D or by culturing the preexposed cells for 4 hr prior to TNF lytic assay. TNF preincubation of N- and S-EL4 cells results in an immediate decrease in 125I-TNF binding due to TNF receptor occupancy. Recovery of TNF-R occupancy and TNF internalization were subsequently noted.
authors.affiliation: Department of Immunology, St. Jude Children's Research Hospital, Memphis, Tennessee 38101-0318.
authors.forename: M
authors.initials: M
authors.lastname: Fishman
authors.forename: M
authors.initials: M
authors.lastname: Costlow
mesh_terms: D000818:Animals; D003513:Cycloheximide / Q000494:pharmacology; D006360:Heat-Shock Proteins / Q000096:biosynthesis; D008262:Macrophage Activation; D051379:Mice; D008810:Mice, Inbred C57BL; D009569:Nitric Oxide / Q000096:biosynthesis; D018124:Receptors, Tumor Necrosis Factor / Q000378:metabolism; D011994:Recombinant Proteins / Q000494:pharmacology; D013945:Thymoma / Q000473:pathology; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D006360:Heat-Shock Proteins; D018124:Receptors, Tumor Necrosis Factor; D011994:Recombinant Proteins; D014409:Tumor Necrosis Factor-alpha; D009569:Nitric Oxide; D003513:Cycloheximide