1. [Interferon-γ Induced by Toxoplasma gondii Excreted/Secreted Antigens Promotes Apoptosis of CD4+CD25+ Regulatory T Cells].
- Author
-
Ge K, Qiu XY, Wang LJ, Chen H, Zhang LY, Qiu JF, and Wang Y
- Subjects
- Animals, Apoptosis, Enzyme-Linked Immunosorbent Assay, Flow Cytometry, Interferon-gamma, Mice, Mice, Inbred C57BL, Spleen, T-Lymphocytes, Regulatory, Toxoplasma
- Abstract
Objective: To investigate the effect of excreted/secreted antigens (ESAs) from Toxoplasma gondii RH strain and TgCtwh3 strain on apoptosis of CD4+CD25+ regulatory T cells and interferon-γ (IFN-γ) secretion., Methods: ESAs of Toxoplasma gondii RH strain and TgCtwh3 strain were prepared. Splenic mononuclear cells were isolated from C57BL/6 mice and randomly divided into RH ESA group(2×106 cells/well with addition of 10 μg/ml RH ESA), TgCtwh3 ESA group (2×106 cells/well with addition of 10 μg/ml TgCtwh3 ESA) and control group(2×106 cells/well with addition of 10 μg/ml ovalbumin). Flow cytometry was performed to examine the early apoptosis of CD4+CD25+ regulatory T cells after treatment for 48 h and 72 h. ELISA was conducted to determine the level of IFN-γ in the supernatant after treatment for 72 h. In another experiment, the 3 groups of splenic mononuclear cells were added with 10 μg/ml anti-IFN-γ antibody for 72 h and flow cytometry was performed to examine the early apoptosis of CD4+CD25+ regulatory T cells. Meanwhile, splenic mononuclear cells from IFN-γ knockout and wild-type C57BL/6 mice were also divided into the above-described 3 groups, and flow cytometry was performed to examine the early apoptosis of CD4+CD25+ regulatory T cells after treatment for 72 h., Results: The concentrations of RH ESA and TgCtwh3 ESA were 0.54 mg/ml and 2.14 mg/ml, respectively. Flow cytometry showed that the early apoptosis rate of CD4+CD25+ regulatory T cells in the RH ESA group and the TgCtwh3 ESA group after 48 h treatment was (12.90±1.26)% and (9.71±1.04)%, respectively (P<0.05), both significantly higher than that in control group (4.48±0.48)% (P<0.01) . The early apoptosis rate of CD4+CD25+ regulatory T cells after 72 h in the RH ESA group was(15.21±1.11)%, significantly higher than that in the TgCtwh3 ESA group[(11.02±0.92)%] (P<0.05) and the control group[(10.10±1.49)%](P<0.01). ELISA showed that the level of interferon-γ in the RH ESA group and the TgCtwh3 ESA group after 72 h was(4 764.0±118.7) pg/ml and (3 629.0±33.6) pg/ml, respectively (P<0.01), both significantly higher than that in the control[(679.4±30.6) pg/ml](P<0.01). Flow cytometry revealed lower early apoptosis rate of CD4+CD25+ regulatory T cells in the RH ESA group added with anti-IFN-γ antibody[(10.44±1.44)%] compared with that without the addition of the antibody[(14.96±0.83)](P<0.05). But this difference was not observed for the TgCtwh3 ESA group. Moreover, the RH ESA-induced apoptosis rate of regulatory T cells from IFN-γ knockout mice[(10.64±0.55)%] was significantly lower than that from the wild-type mice [(15.21±1.11)%](P<0.01). But this difference was not found for the TgCtwh3 ESA treatment., Conclusion: T. gondii RH ESA induces apoptosis of CD4+CD25+ regulatory T cells and IFN-γ secretion, and these effects are stronger than those of TgCtwh3 ESA. The T. gondii ESA-induced IFN-γ stimulates generation of anti-Toxoplasma immunity during acute Toxoplasma infection through mediation of regulatory T cell apoptosis.
- Published
- 2016