Antileishmanial defense in macrophages triggered by tumor necrosis factor expressed on CD4+ T lymphocyte plasma membrane.
In our studies of host defense to the intracellular protozoan Leishmania major, we uncovered a novel mechanism of antileishmanial defense that involves direct cell contact between effector CD4+ lymphocytes and Leishmania-infected macrophages. The mechanism is distinctive because it does not involve lymphokine secretion and induces no cytotoxic effects in the host cells; its expression is antigen-specific and genetically restricted. We now demonstrate that these effector CD4+ cells display tumor necrosis factor (TNF) on their surface and provide evidence that the membrane-associated TNF is involved in the activation of the antileishmanial defense. Using a Leishmania-specific cloned T-T cell hybridoma line (1B6; CD4+, T helper type 1) that activates antileishmanial defense in macrophages through cell contact and does not secrete TNF, we noted that only cells bearing surface TNF (TNF+), but not ones lacking surface TNF (TNF-), exerted these effects. Moreover, the antileishmanial effects excreted by TNF+ 1B6 cells as well as by lymph node CD4+ TNF+ lymphocytes could be blocked with anti-TNF antibody. We propose that membrane-associated TNF on CD4+ T cells may provide a mechanism of targeting activation signals to macrophages in an antigen-specific and genetically restricted manner.
Sypek
J P
JP
Department of Medicine, New England Medical Center Hospitals, Boston, Massachusetts.
Wyler
D J
DJ
D000818:Animals; D000913:Antibodies, Protozoan / Q000276:immunology; D015153:Blotting, Western; D015704:CD4 Antigens / Q000276:immunology; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D002462:Cell Membrane / Q000276:immunology; D005260:Female; D007895:Leishmania tropica / Q000276:immunology*; D016773:Leishmaniasis, Cutaneous / Q000276:immunology*; D008262:Macrophage Activation; D008264:Macrophages / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D008815:Mice, Inbred Strains; D014409:Tumor Necrosis Factor-alpha / Q000032:analysis / Q000502:physiology*
D000913:Antibodies, Protozoan; D015704:CD4 Antigens; D014409:Tumor Necrosis Factor-alpha