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GITR Activation Positively Regulates Immune Responses against Toxoplasma gondii.

Costa FR, Mota CM, Santiago FM, Silva MV, Ferreira MD, Fonseca DM, Silva JS, Mineo JR, Mineo TW - PLoS ONE (2016)

Bottom Line: Toxoplasma gondii is a widespread parasite responsible for causing clinical diseases especially in pregnant and immunosuppressed individuals.Glucocorticoid-induced TNF receptor (GITR), which is also known as TNFRS18 and belongs to the TNF receptor superfamily, is found to be expressed in various cell types of the immune system and provides an important costimulatory signal for T cells and myeloid cells.Interestingly, mice infected and treated with an agonistic antibody anti-GITR (DTA-1) presented a robust increase in pro-inflammatory cytokine production at preferential sites of parasite replication, which was associated with the decrease in latent brain parasitism of mice under treatment with DTA-1.

View Article: PubMed Central - PubMed

Affiliation: Laboratório de Imunoparasitologia "Dr. Mário Endsfeldz Camargo", Instituto de Ciências Biomédicas, Universidade Federal de Uberlândia, Av. Amazonas s/n, Bloco 4C, Sala 4C01, 38405-320, Uberlândia, Minas Gerais, Brazil.

ABSTRACT
Toxoplasma gondii is a widespread parasite responsible for causing clinical diseases especially in pregnant and immunosuppressed individuals. Glucocorticoid-induced TNF receptor (GITR), which is also known as TNFRS18 and belongs to the TNF receptor superfamily, is found to be expressed in various cell types of the immune system and provides an important costimulatory signal for T cells and myeloid cells. However, the precise role of this receptor in the context of T. gondii infection remains elusive. Therefore, the current study investigated the role of GITR activation in the immunoregulation mechanisms induced during the experimental infection of mice with T. gondii. Our data show that T. gondii infection slightly upregulates GITR expression in Treg cells and B cells, but the most robust increment in expression was observed in macrophages and dendritic cells. Interestingly, mice infected and treated with an agonistic antibody anti-GITR (DTA-1) presented a robust increase in pro-inflammatory cytokine production at preferential sites of parasite replication, which was associated with the decrease in latent brain parasitism of mice under treatment with DTA-1. Several in vivo and in vitro analysis were performed to identify the cellular mechanisms involved in GITR activation upon infection, however no clear alterations were detected in the phenotype/function of macrophages, Tregs and B cells under treatment with DTA-1. Therefore, GITR appears as a potential target for intervention during infection by the parasite Toxoplasma gondii, even though further studies are still necessary to better characterize the immune response triggered by GITR activation during T. gondii infection.

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GITR expression in the lymphocyte compartment.Splenocytes from naïve C57BL/6 mice were collected, stimulated or not with tachyzoites of the ME-49 strain at different MOIs (MOI: 0.1; 0.01 and 0.001) and kept in culture for 24 hours. GITR expression was then analyzed by flow cytometry. Gating strategy is depicted in (A), histogram plots in (B) and MFI expression in (C). The lymphocytes were first identified and gated based on their FSC and SSC profile after doublets exclusion. Treg cells were considered as CD3+CD4+Foxp3+ T cells gated on the lymphocyte region. Error bars indicate mean +/- SEM. *P < 0.05 and **P < 0.01. The experiment was performed twice with six technical replicates in each experiment.
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pone.0152622.g001: GITR expression in the lymphocyte compartment.Splenocytes from naïve C57BL/6 mice were collected, stimulated or not with tachyzoites of the ME-49 strain at different MOIs (MOI: 0.1; 0.01 and 0.001) and kept in culture for 24 hours. GITR expression was then analyzed by flow cytometry. Gating strategy is depicted in (A), histogram plots in (B) and MFI expression in (C). The lymphocytes were first identified and gated based on their FSC and SSC profile after doublets exclusion. Treg cells were considered as CD3+CD4+Foxp3+ T cells gated on the lymphocyte region. Error bars indicate mean +/- SEM. *P < 0.05 and **P < 0.01. The experiment was performed twice with six technical replicates in each experiment.

Mentions: Since different cells of the immune system may express GITR, changes in receptor expression were evaluated in both innate and adaptive immune cells in the context of T. gondii infection in vitro. For that, spleen cells from naïve WT C57BL/6 mice were co-cultured with T. gondii tachyzoites using different MOIs (0.1, 0.01 and 0.001) for 24h and analyzed by flow cytometry. The starting point at MOI of 0.1 was standardized in-house, in order to reflect a more physiological condition, since macrophage/dendritic cell populations represent between 10–20% of the immune cells contained within the spleen of a mouse. Gating strategy is depicted in Figs 1A and 2A. We observed a slight increase in GITR expression in Treg cells (CD3+CD4+Foxp3+—Fig 1B and 1C) and B cells (CD19+—Fig 1B and 1C). Surprisingly, we detected a robust increase in GITR expression after stimulation with ME-49 tachyzoites in macrophages (F4/80+CD11b+—Fig 2B and 2C) and, in a lesser extent, dendritic cells (F4/80-CD11c+—Fig 2B and 2C). GITR expression in NK and NKT cells remained unaltered after stimulation (data not shown). Collectively, these results suggest that GITR signaling may affect multiple cell lines during immune responses mounted against T. gondii.


GITR Activation Positively Regulates Immune Responses against Toxoplasma gondii.

Costa FR, Mota CM, Santiago FM, Silva MV, Ferreira MD, Fonseca DM, Silva JS, Mineo JR, Mineo TW - PLoS ONE (2016)

GITR expression in the lymphocyte compartment.Splenocytes from naïve C57BL/6 mice were collected, stimulated or not with tachyzoites of the ME-49 strain at different MOIs (MOI: 0.1; 0.01 and 0.001) and kept in culture for 24 hours. GITR expression was then analyzed by flow cytometry. Gating strategy is depicted in (A), histogram plots in (B) and MFI expression in (C). The lymphocytes were first identified and gated based on their FSC and SSC profile after doublets exclusion. Treg cells were considered as CD3+CD4+Foxp3+ T cells gated on the lymphocyte region. Error bars indicate mean +/- SEM. *P < 0.05 and **P < 0.01. The experiment was performed twice with six technical replicates in each experiment.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4814089&req=5

pone.0152622.g001: GITR expression in the lymphocyte compartment.Splenocytes from naïve C57BL/6 mice were collected, stimulated or not with tachyzoites of the ME-49 strain at different MOIs (MOI: 0.1; 0.01 and 0.001) and kept in culture for 24 hours. GITR expression was then analyzed by flow cytometry. Gating strategy is depicted in (A), histogram plots in (B) and MFI expression in (C). The lymphocytes were first identified and gated based on their FSC and SSC profile after doublets exclusion. Treg cells were considered as CD3+CD4+Foxp3+ T cells gated on the lymphocyte region. Error bars indicate mean +/- SEM. *P < 0.05 and **P < 0.01. The experiment was performed twice with six technical replicates in each experiment.
Mentions: Since different cells of the immune system may express GITR, changes in receptor expression were evaluated in both innate and adaptive immune cells in the context of T. gondii infection in vitro. For that, spleen cells from naïve WT C57BL/6 mice were co-cultured with T. gondii tachyzoites using different MOIs (0.1, 0.01 and 0.001) for 24h and analyzed by flow cytometry. The starting point at MOI of 0.1 was standardized in-house, in order to reflect a more physiological condition, since macrophage/dendritic cell populations represent between 10–20% of the immune cells contained within the spleen of a mouse. Gating strategy is depicted in Figs 1A and 2A. We observed a slight increase in GITR expression in Treg cells (CD3+CD4+Foxp3+—Fig 1B and 1C) and B cells (CD19+—Fig 1B and 1C). Surprisingly, we detected a robust increase in GITR expression after stimulation with ME-49 tachyzoites in macrophages (F4/80+CD11b+—Fig 2B and 2C) and, in a lesser extent, dendritic cells (F4/80-CD11c+—Fig 2B and 2C). GITR expression in NK and NKT cells remained unaltered after stimulation (data not shown). Collectively, these results suggest that GITR signaling may affect multiple cell lines during immune responses mounted against T. gondii.

Bottom Line: Toxoplasma gondii is a widespread parasite responsible for causing clinical diseases especially in pregnant and immunosuppressed individuals.Glucocorticoid-induced TNF receptor (GITR), which is also known as TNFRS18 and belongs to the TNF receptor superfamily, is found to be expressed in various cell types of the immune system and provides an important costimulatory signal for T cells and myeloid cells.Interestingly, mice infected and treated with an agonistic antibody anti-GITR (DTA-1) presented a robust increase in pro-inflammatory cytokine production at preferential sites of parasite replication, which was associated with the decrease in latent brain parasitism of mice under treatment with DTA-1.

View Article: PubMed Central - PubMed

Affiliation: Laboratório de Imunoparasitologia "Dr. Mário Endsfeldz Camargo", Instituto de Ciências Biomédicas, Universidade Federal de Uberlândia, Av. Amazonas s/n, Bloco 4C, Sala 4C01, 38405-320, Uberlândia, Minas Gerais, Brazil.

ABSTRACT
Toxoplasma gondii is a widespread parasite responsible for causing clinical diseases especially in pregnant and immunosuppressed individuals. Glucocorticoid-induced TNF receptor (GITR), which is also known as TNFRS18 and belongs to the TNF receptor superfamily, is found to be expressed in various cell types of the immune system and provides an important costimulatory signal for T cells and myeloid cells. However, the precise role of this receptor in the context of T. gondii infection remains elusive. Therefore, the current study investigated the role of GITR activation in the immunoregulation mechanisms induced during the experimental infection of mice with T. gondii. Our data show that T. gondii infection slightly upregulates GITR expression in Treg cells and B cells, but the most robust increment in expression was observed in macrophages and dendritic cells. Interestingly, mice infected and treated with an agonistic antibody anti-GITR (DTA-1) presented a robust increase in pro-inflammatory cytokine production at preferential sites of parasite replication, which was associated with the decrease in latent brain parasitism of mice under treatment with DTA-1. Several in vivo and in vitro analysis were performed to identify the cellular mechanisms involved in GITR activation upon infection, however no clear alterations were detected in the phenotype/function of macrophages, Tregs and B cells under treatment with DTA-1. Therefore, GITR appears as a potential target for intervention during infection by the parasite Toxoplasma gondii, even though further studies are still necessary to better characterize the immune response triggered by GITR activation during T. gondii infection.

Show MeSH
Related in: MedlinePlus