The interaction between CD8+ cytotoxic T cells and Leishmania-infected macrophages.
Leishmania is resident within the macrophages of its vertebrate host. In any intramacrophage infection, where the pathogen is present in a form capable of mediating cell to cell transmission, the contribution of a cytotoxic T cell response to protective immunity is questionable. This study presents data from an in vitro model designed to elucidate the outcome of an interaction between CD8+, cytotoxic T cells and infected macrophages. Experiments were conducted with an H-2d-restricted, cytotoxic CD8+ T cell clone and Leishmania parasites present in mixed macrophage cultures, with the parasites confined to either histocompatible BALB/c macrophages, or incompatible CBA macrophages. Initial experiments indicated that the viability of Leishmania was unaffected by the lysis of its host macrophage by cytotoxic T cells. However, extended experiments showed that the parasites were killed between 24 and 72 h. The same results were obtained regardless of whether the parasites were resident in the target, BALB/c, macrophages or the bystander, CBA, macrophages. Addition of neutralizing, anti-IFN-g antibody to the cultures ablated most of the leishmanicidal behavior, indicating that parasite death was attributable to macrophage activation, resulting from cytokine secretion from the T cells following the initial recognition event.
Smith
L E
LE
Department of Pathology, New York University Medical Center, New York 10016.
Rodrigues
M
M
Russell
D G
DG
D000818:Animals; D000945:Antigens, Differentiation, T-Lymphocyte / Q000032:analysis; D016827:CD8 Antigens; D002999:Clone Cells; D003602:Cytotoxicity, Immunologic; D007111:Immunity, Cellular; D007371:Interferon-gamma / Q000502:physiology; D007894:Leishmania mexicana / Q000276:immunology*; D007896:Leishmaniasis / Q000276:immunology*; D008264:Macrophages / Q000276:immunology / Q000469:parasitology*; D051379:Mice; D008815:Mice, Inbred Strains; D010529:Peritoneal Cavity / Q000166:cytology; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*
D000945:Antigens, Differentiation, T-Lymphocyte; D016827:CD8 Antigens; D007371:Interferon-gamma