During Trypanosoma cruzi infection CD1d-restricted NK T cells limit parasitemia and augment the antibody response to a glycophosphoinositol-modified surface protein - PubMed (original) (raw)

During Trypanosoma cruzi infection CD1d-restricted NK T cells limit parasitemia and augment the antibody response to a glycophosphoinositol-modified surface protein

Malcolm S Duthie et al. Infect Immun. 2002 Jan.

Abstract

Trypanosoma cruzi is a protozoan parasite that chronically infects many mammalian species and in humans causes Chagas' disease, a chronic inflammatory disease. The parasite expresses glycophosphoinositol (GPI), which potently stimulates interleukin 12 (IL-12) production. During T. cruzi infection IL-12, and possibly GPI, might stimulate NK T cells to affect the protective and chronic inflammatory responses. Here we report that during T. cruzi infection CD1d-restricted NK T cells are stimulated as NK T-cell-deficient mice have greater parasitemia. Furthermore, during T. cruzi infection the percentages of NK T cells in the liver and spleen become decreased for prolonged periods of time, and in vitro stimulation of NK T cells derived from livers of chronically infected mice, compared to uninfected mice, results in increased gamma interferon and IL-4 secretion. Moreover, in NK T-cell-deficient mice the chronic-phase antibody response to a GPI-modified surface protein is decreased. These results indicate that, during the acute infection, NK T cells limit parasitemia and that, during the chronic phase, NK T cells augment the antibody response. Thus, during T. cruzi infection the quality of an individual's NK T-cell response can affect the level of parasitemia and parasite tissue burden, the intensity of the chronic inflammatory responses, and possibly the outcome of Chagas' disease.

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Figures

FIG. 1.

FIG. 1.

During acute T. cruzi infection NK T-cell-deficient mice have increased parasitemia. In these experiments groups of five mice were infected with T. cruzi and parasitemia was monitored. (a) C57BL/6 CD1d+/− or CD1d−/− mice; (b) C57BL/6 CD1d+/−, CD1d−/−, or Jα281−/− mice; (c) BALB/c wild-type or Jα281−/− mice. C57BL/6 mice were infected with 105 trypomastigotes (a and b), and BALB/c mice were infected with 5 × 104 trypomastigotes (c). (c) On day 68 of the infection (arrow) the mice received a second inoculation of 106 trypomastigotes. The mean parasitemia and SEM (error bar) per group are shown. The cumulative parasitemia for each group was compared: (a) P < 0.005; (b) CD1d−/− or Jα281−/− versus CD1d+/−, P < 0.001; (c) P < 0.001.

FIG. 2.

FIG. 2.

During T. cruzi infection liver and spleen NK T-cell and NK cell population sizes are decreased. C57BL/6 mice were infected with 105 trypomastigotes, and at the indicated days of the infection liver and spleen mononuclear cells were stained with fluorescent MAbs to NK1.1 and CD3. (a) Each plot presents data of an individual representative mouse. (b and c) The mean percentages of NK T cells (CD3+ NK1.1+) (total bars) or CD4+ NK1.1+ cells (black bars) in livers (b) and spleens (c) of several mice are shown. The numbers above the bars indicate the number of mice analyzed on that day of the infection. (d) The mean percentages of NK cells (CD3− NK1.1+) in livers (circles) or spleens (squares) are shown. On the different days of the infection the same numbers of livers or spleens were analyzed as indicated in panels b and c. Symbols: *, P < 0.05; **, P < 0.01 versus preinfection (day 0). Error bars (b, c, and d), SEM.

FIG. 2.

FIG. 2.

During T. cruzi infection liver and spleen NK T-cell and NK cell population sizes are decreased. C57BL/6 mice were infected with 105 trypomastigotes, and at the indicated days of the infection liver and spleen mononuclear cells were stained with fluorescent MAbs to NK1.1 and CD3. (a) Each plot presents data of an individual representative mouse. (b and c) The mean percentages of NK T cells (CD3+ NK1.1+) (total bars) or CD4+ NK1.1+ cells (black bars) in livers (b) and spleens (c) of several mice are shown. The numbers above the bars indicate the number of mice analyzed on that day of the infection. (d) The mean percentages of NK cells (CD3− NK1.1+) in livers (circles) or spleens (squares) are shown. On the different days of the infection the same numbers of livers or spleens were analyzed as indicated in panels b and c. Symbols: *, P < 0.05; **, P < 0.01 versus preinfection (day 0). Error bars (b, c, and d), SEM.

FIG. 2.

FIG. 2.

During T. cruzi infection liver and spleen NK T-cell and NK cell population sizes are decreased. C57BL/6 mice were infected with 105 trypomastigotes, and at the indicated days of the infection liver and spleen mononuclear cells were stained with fluorescent MAbs to NK1.1 and CD3. (a) Each plot presents data of an individual representative mouse. (b and c) The mean percentages of NK T cells (CD3+ NK1.1+) (total bars) or CD4+ NK1.1+ cells (black bars) in livers (b) and spleens (c) of several mice are shown. The numbers above the bars indicate the number of mice analyzed on that day of the infection. (d) The mean percentages of NK cells (CD3− NK1.1+) in livers (circles) or spleens (squares) are shown. On the different days of the infection the same numbers of livers or spleens were analyzed as indicated in panels b and c. Symbols: *, P < 0.05; **, P < 0.01 versus preinfection (day 0). Error bars (b, c, and d), SEM.

FIG. 3.

FIG. 3.

The proliferative response following α-GalCer stimulation of liver and spleen cells isolated from _T. cruzi_-infected mice. Wild-type C57BL/6 mice were infected with 105 trypomastigotes and at different days of the infection liver (a) or spleen (b) cells were isolated and cultured for 72 h in the presence of α-GalCer (100 ng/ml) or diluent only. [3H]thymidine was added for the last 24 h. (a and b) The mean proliferation index and SEM of three independent experiments are presented. In each independent experiment each sample was analyzed in triplicate, and the mean value was used to calculate the proliferation index. (c and d) The mean proliferation index is divided by the mean percentage of NK T cells. The percentage of NK T cells was determined as described in the legend to Fig. 2. Symbols: *, P < 0.05; **, P < 0.01 compared to uninfected mice (day 0).

FIG. 4.

FIG. 4.

IFN-γ and IL-4 production following α-GalCer stimulation of liver or spleen cells isolated from _T. cruzi_-infected mice. (a and b) Liver cells (closed circles) and spleen cells (open circles) were prepared from wild-type C57BL/6 mice that were uninfected or infected (105 trypomastigotes) for 3 or 14 days. Data of one of three experiments with similar results are presented. (c and d) Cells from uninfected mice (open bars) or mice infected (closed bars) (105 trypomastigotes) for 90 to 120 days were incubated at 3 × 105 per well for 96 h in media with α-GalCer (100 ng/ml) or diluent only, and the supernatants were analyzed by ELISA for IFN-γ or IL-4. The mean data of eight mice derived from three independent experiments are presented. The data represent cytokines detected following α-GalCer incubation minus cytokines detected following diluent-only incubation. Following diluent-only incubation no liver IFN-γ or spleen IL-4 was detected. The amounts of IL-4 detected in liver following diluent-only incubation were as follows: uninfected mice, 59 pg/ml; day 3 of infection, 187 pg/ml; day 14 of infection, 270 pg/ml. The amounts of IFN-γ detected in spleen following diluent-only incubation were as follows: uninfected, 26 pg/ml; day 3 of infection, 0 pg/ml; day 14 of infection, 330 pg/ml.

FIG. 5.

FIG. 5.

Comparison of antibody responses of chronically infected NK T-cell-deficient and normal mice to GPI-modified SA85-1.1 protein. Chronically infected NK T-cell-deficient and normal mice were infected with T. cruzi, and during the chronic phase, serum samples from individual mice were obtained and the anti-SA85-1.1 and anti-trypomastigote IgG and IgG2a antibody concentrations were determined. C57BL/6 mice were infected with 105 trypomastigotes, and BALB/c mice were infected with 5 × 104 trypomastigotes. The bars represent the mean antibody concentration of 10 C57BL/6 CD1d−/−, 10 C57BL/6 CD1d+/−, and 5 C57BL/6 Jα281−/− mice and 5 BALB/c Jα281−/− and 5 BALB/c wild-type mice. Symbols: *, P < 0.05 for NK T-cell-deficient versus CD1d+/− mice; **, P < 0.001 for NK T-cell-deficient mice versus wild-type mice.

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