Evidence for the existence of two forms of membrane tumor necrosis factor: an integral protein and a molecule attached to its receptor.
Plasma membranes were isolated from thioglycolate-induced peritoneal mouse macrophages and tested directly in a 51Cr-release assay against WEHI 164 tumor cells. These membranes showed anti-TNF antibody inhibitable killing of the TNF-sensitive tumor cell line, indicating that membrane-associated TNF is present on mouse macrophages. In order to elucidate whether membrane TNF is an integral protein or a molecule attached to a receptor, cells and plasma membranes were treated with low pH buffer. A partial reduction in TNF activity was observed which could be restored by incubation with exogenous TNF. In a Western blot analysis the integral membrane TNF could be identified as the 26-kDa molecule on activated mouse macrophages. These results indicate that both forms of membrane-associated TNF exist on macrophages and are responsible for cell-mediated cytotoxicity against TNF-alpha-sensitive targets.
Luettig
B
B
Fraunhofer Institute for Toxicology, Hannover, FRG.
Decker
T
T
Lohmann-Matthes
M L
ML
D000818:Animals; D002021:Buffers; D002460:Cell Line; D005998:Glycine; D006863:Hydrogen-Ion Concentration; D008262:Macrophage Activation; D008264:Macrophages / Q000276:immunology / Q000378:metabolism*; D008297:Male; D008565:Membrane Proteins / Q000302:isolation & purification / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D008970:Molecular Weight; D011956:Receptors, Cell Surface / Q000378:metabolism*; D018124:Receptors, Tumor Necrosis Factor; D012995:Solubility; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000302:isolation & purification / Q000378:metabolism*
D002021:Buffers; D008565:Membrane Proteins; D011956:Receptors, Cell Surface; D018124:Receptors, Tumor Necrosis Factor; D014409:Tumor Necrosis Factor-alpha; D005998:Glycine