Tumoricidal effector mechanisms of murine BCG-activated macrophages: role of TNF in conjugation-dependent and conjugation-independent pathways.
The roles of secreted and membrane-associated TNFs were investigated in activated macrophage cytolysis of L929, EMT-6, and P815 targets. While all three targets were susceptible to cytolysis in coculture, an anti-TNF antiserum blocked lysis of L929 and EMT-6 but not of the P815 targets. Of the three targets, recombinant human or mouse TNF could only lyse the L929 target; despite the fact that a role for TNF was invoked in lysis of EMT-6 targets in coculture, the latter was strongly resistant to soluble rTNF, even at concentrations 30-40-fold higher than the Ka for its TNF-receptor. Cytolysis of the L929 target occurred when it was cocultured with BCG-activated macrophages even when these effector cells did not secrete TNF, either due to prior chemical crosslinking or to lack of exposure to a triggering level of lipopolysaccharide. Furthermore, by introduction of the anti-TNF antiserum over a dose-range, it was shown that macrophage cytolysis both of L929 and EMT-6 targets occurred in the absence of bioavailable, fluid-phase TNF. Thus, even for targets susceptible to fluid-phase TNF, TNF-dependent, direct macrophage-mediated cytolysis appears to be a function independent of secreted TNF and one that utilizes effector-target contact to express the action of a membrane form of the molecule.
Klostergaard
J
J
Department of Tumor Biology, University of Texas M.D. Anderson Cancer Center, Houston 77030.
Stoltje
P A
PA
Kull
F C
FC
D000818:Animals; D003227:Conjugation, Genetic / Q000502:physiology; D003603:Cytotoxins / Q000502:physiology; D005347:Fibroblasts / Q000502:physiology / Q000648:ultrastructure; D007106:Immune Sera / Q000276:immunology; D007370:Interferon Type I / Q000276:immunology; D008262:Macrophage Activation; D008264:Macrophages / Q000502:physiology* / Q000648:ultrastructure; D008297:Male; D051379:Mice; D009163:Mycobacterium bovis / Q000502:physiology*; D010641:Phenotype; D011956:Receptors, Cell Surface / Q000378:metabolism; D018124:Receptors, Tumor Necrosis Factor; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology / Q000378:metabolism / Q000502:physiology
D003603:Cytotoxins; D007106:Immune Sera; D007370:Interferon Type I; D011956:Receptors, Cell Surface; D018124:Receptors, Tumor Necrosis Factor; D014409:Tumor Necrosis Factor-alpha