Antigen-specific (p30) mouse CD8+ T cells are cytotoxic against Toxoplasma gondii-infected peritoneal macrophages.
The importance of CD8+ T cells in immunity against Toxoplasma gondii is now well recognized. The mechanism by which these CD8+ T cells are able to confer this immunity is not yet understood. To examine the Ag specificity of this response, immune splenocytes from mice immunized with p30, a major surface parasite Ag, were evaluated for their ability to lyse peritoneal macrophages infected with three different strains of T. gondii. Macrophages infected with either the RH or P wild-type strain tachyzoites were lysed at varying E:T ratios by nylon wool nonadherent immune splenocytes whereas macrophages infected with a p30-deficient mutant (B mutant) of the P strain were not. The gene encoding p30 for the wild type and B mutant were amplified by the polymerase chain reaction. This revealed a nonsense mutation in the B mutant such that its primary translation product is predicted to be about two-thirds the size of the wild-type p30 molecule. mAb depletion studies indicate that the cytotoxic effect of the immune splenocytes is mediated by the CD8+ T cell population. Peritoneal macrophages infected with the three different strains (RH, P wild type, B mutant) from mice genetically restricted were not lysed by the immune CD8+ effector cell population. A cloned line (C3) of p30 Ag-specific CD8+ T cells exhibited significant cytotoxicity against syngeneic peritoneal macrophages infected with either the RH or P strain tachyzoites. There was no macrophage lysis observed by these CD8+ effector cells of either syngeneic macrophages infected with the B mutant or nonsyngeneic macrophages infected with the three different tachyzoite strains.
Kasper
L H
LH
Department of Medicine, Dartmouth Medical School, Hanover, NH 03756.
Khan
I A
IA
Ely
K H
KH
Buelow
R
R
Boothroyd
J C
JC
D000595:Amino Acid Sequence; D000818:Animals; D000953:Antigens, Protozoan / Q000276:immunology*; D001483:Base Sequence; D016827:CD8 Antigens / Q000032:analysis*; D007114:Immunization; D008264:Macrophages / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D009154:Mutation; D015800:Protozoan Proteins / Q000276:immunology*; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*; D014122:Toxoplasma / Q000276:immunology*; D014124:Toxoplasmosis, Animal / Q000276:immunology*
D000953:Antigens, Protozoan; D016827:CD8 Antigens; D015800:Protozoan Proteins; C047168:SAG1 antigen, Toxoplasma