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Interleukin-6 is crucial for recall of influenza-specific memory CD4 T cells.

Longhi MP, Wright K, Lauder SN, Nowell MA, Jones GW, Godkin AJ, Jones SA, Gallimore AM - PLoS Pathog. (2008)

Bottom Line: Specifically, we find that CD4+ but not CD8+ T cell memory is critically dependent upon IL-6.This effect of IL-6 includes its ability to suppress CD4+CD25+ regulatory T cells (Treg).We demonstrate that influenza-induced IL-6 limits the activity of virus-specific Tregs, thereby facilitating the activity of virus-specific memory CD4+ T cells.

View Article: PubMed Central - PubMed

Affiliation: Medical Biochemistry and Immunology, School of Medicine, Cardiff University, Heath Park, Cardiff, United Kingdom.

ABSTRACT
Currently, our understanding of mechanisms underlying cell-mediated immunity and particularly of mechanisms that promote robust T cell memory to respiratory viruses is incomplete. Interleukin (IL)-6 has recently re-emerged as an important regulator of T cell proliferation and survival. Since IL-6 is abundant following infection with influenza virus, we analyzed virus-specific T cell activity in both wild type and IL-6 deficient mice. Studies outlined herein highlight a novel role for IL-6 in the development of T cell memory to influenza virus. Specifically, we find that CD4+ but not CD8+ T cell memory is critically dependent upon IL-6. This effect of IL-6 includes its ability to suppress CD4+CD25+ regulatory T cells (Treg). We demonstrate that influenza-induced IL-6 limits the activity of virus-specific Tregs, thereby facilitating the activity of virus-specific memory CD4+ T cells. These experiments reveal a critical role for IL-6 in ensuring, within the timeframe of an acute infection with a cytopathic virus, that antigen-specific Tregs have no opportunity to down-modulate the immune response, thereby favoring pathogen clearance and survival of the host.

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Related in: MedlinePlus

Influenza-specific suppressor activity in WT and IL-6βˆ’/βˆ’ mice.Mice were infected i.n. with 20 HAU of influenza virus (H17). Eight weeks after infection, splenocytes from WT and IL6βˆ’/βˆ’ mice were harvested. (A) Purified CD4+ T cells were tested for proliferation against inactivated H17 before (ND) or after (D) depletion of CD25+ T cells. Influenza-specific proliferation in both populations was measured by [3H]-thymidine incorporation at day 5. Each symbol represents an individual mouse and the lines join responses in undepleted (ND) and CD25-depleted (D) CD4+ T cell populations. A stimulation index greater than 2 was considered a positive response. (B) CD4+CD25+ cells from WT and IL-6βˆ’/βˆ’ mice, infected 2 or 8 weeks previously, were isolated from splenocytes and their suppressive capacity was evaluated by incubation at a ratio of 1∢1 with CD4+ T cells from a WT mouse infected 2 weeks previously with H17 influenza virus. The cells were stimulated with either APCs exposed to 1 Β΅g/ml anti-CD3 mAbs (B) or influenza infected APCs (C and D). Proliferation was measured by [3H]-thymidine incorporation at day 5. CD4+CD25+ cells from 4 individual WT and IL-6βˆ’/βˆ’mice were analyzed and each bar represents the mean valueΒ±SEM of each group. Statistical significance was evaluated using the Students t test.
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ppat-1000006-g007: Influenza-specific suppressor activity in WT and IL-6βˆ’/βˆ’ mice.Mice were infected i.n. with 20 HAU of influenza virus (H17). Eight weeks after infection, splenocytes from WT and IL6βˆ’/βˆ’ mice were harvested. (A) Purified CD4+ T cells were tested for proliferation against inactivated H17 before (ND) or after (D) depletion of CD25+ T cells. Influenza-specific proliferation in both populations was measured by [3H]-thymidine incorporation at day 5. Each symbol represents an individual mouse and the lines join responses in undepleted (ND) and CD25-depleted (D) CD4+ T cell populations. A stimulation index greater than 2 was considered a positive response. (B) CD4+CD25+ cells from WT and IL-6βˆ’/βˆ’ mice, infected 2 or 8 weeks previously, were isolated from splenocytes and their suppressive capacity was evaluated by incubation at a ratio of 1∢1 with CD4+ T cells from a WT mouse infected 2 weeks previously with H17 influenza virus. The cells were stimulated with either APCs exposed to 1 Β΅g/ml anti-CD3 mAbs (B) or influenza infected APCs (C and D). Proliferation was measured by [3H]-thymidine incorporation at day 5. CD4+CD25+ cells from 4 individual WT and IL-6βˆ’/βˆ’mice were analyzed and each bar represents the mean valueΒ±SEM of each group. Statistical significance was evaluated using the Students t test.

Mentions: Since IL-6 has been shown to abrogate suppression by Tregs [9] and to suppress Treg development by TGFΞ² [10], we postulated that influenza-virus Treg activity would be more readily detectable in IL-6βˆ’/βˆ’ mice than WT mice and that these cells would suppress the activity of virus-specific memory T cells. To test this hypothesis, we first carried out proliferation assays using purified CD4+ T cells depleted of CD25+ cells from both WT and IL-6βˆ’/βˆ’ mice. In this respect, depletion of CD25+ cells had a variable affect on proliferative responses observed in WT mice, removal of CD25+ cells uncovered influenza-specific memory CD4+ T cell responses in the majority of IL-6βˆ’/βˆ’ mice (Figure 7A). This experiment revealed that influenza-specific proliferative responses can be detected in IL-6βˆ’/βˆ’ mice and suggest that these responses, and to a lesser extent, responses in WT mice, are subject to suppression by Tregs. To more closely examine the responsiveness of Tregs in IL-6βˆ’/βˆ’ mice, we performed suppression assays designed to compare 1) Treg activity following polyclonal stimulation of the cells using CD3-specific mAbs (Figure 7B) and 2) influenza-specific Treg activity (Figures 7C and D) in both groups of mice. Suppression assays were carried out using CD4+CD25+ Tregs purified from WT and IL-6βˆ’/βˆ’ mice infected 2 (Figure 7C) and 8 weeks (Figure 7D) previously with influenza virus. CD4+CD25+ T cells derived from these mice were incubated with CD4+CD25βˆ’ T cells from a WT mouse infected two weeks earlier with influenza virus. These T-cell cultures were then stimulated in vitro with either influenza infected APCs or uninfected APCs. Influenza-specific proliferation was measured by [3H]-thymidine incorporation at day 5. As shown in Figures 7C and D, CD4+CD25+ Tregs isolated from IL-6βˆ’/βˆ’, but not WT mice infected 8 weeks (7D) but not 2 weeks (7C) previously with influenza virus, were able to suppress proliferation of WT influenza-specific CD4+ T cells. This data is consistent with our earlier observation that memory but not primary responses are impaired in influenza-infected IL-6βˆ’/βˆ’ mice and further supports the view that IL-6 has an inhibitory effect on the activity of virus-specific Tregs. We were unable to detect a greater increase in the number of Tregs (by Foxp3 staining) in the lymph nodes or spleens of influenza-infected IL-6βˆ’/βˆ’ compared to WT mice. The number of influenza-specific Treg may be very low thus detecting an increase in cell number in the overall Treg population as a result of the influenza virus infection might not be possible. No significant difference was observed in the ability of WT and IL-6βˆ’/βˆ’ CD4+CD25+ Tregs to suppress CD4+CD25βˆ’ T cell proliferation after stimulation with CD3-specific antibodies (Figure 7B) indicating that there is no inherent failure of Tregs to perform immunosuppressive functions in the IL-6βˆ’/βˆ’ mice. Overall, these data clearly indicate that influenza-specific CD4+ T cells, from both WT and IL-6βˆ’/βˆ’ mice, can be suppressed by Tregs, and reveal a crucial role for IL-6 in inhibiting the activity of virus-specific Tregs.


Interleukin-6 is crucial for recall of influenza-specific memory CD4 T cells.

Longhi MP, Wright K, Lauder SN, Nowell MA, Jones GW, Godkin AJ, Jones SA, Gallimore AM - PLoS Pathog. (2008)

Influenza-specific suppressor activity in WT and IL-6βˆ’/βˆ’ mice.Mice were infected i.n. with 20 HAU of influenza virus (H17). Eight weeks after infection, splenocytes from WT and IL6βˆ’/βˆ’ mice were harvested. (A) Purified CD4+ T cells were tested for proliferation against inactivated H17 before (ND) or after (D) depletion of CD25+ T cells. Influenza-specific proliferation in both populations was measured by [3H]-thymidine incorporation at day 5. Each symbol represents an individual mouse and the lines join responses in undepleted (ND) and CD25-depleted (D) CD4+ T cell populations. A stimulation index greater than 2 was considered a positive response. (B) CD4+CD25+ cells from WT and IL-6βˆ’/βˆ’ mice, infected 2 or 8 weeks previously, were isolated from splenocytes and their suppressive capacity was evaluated by incubation at a ratio of 1∢1 with CD4+ T cells from a WT mouse infected 2 weeks previously with H17 influenza virus. The cells were stimulated with either APCs exposed to 1 Β΅g/ml anti-CD3 mAbs (B) or influenza infected APCs (C and D). Proliferation was measured by [3H]-thymidine incorporation at day 5. CD4+CD25+ cells from 4 individual WT and IL-6βˆ’/βˆ’mice were analyzed and each bar represents the mean valueΒ±SEM of each group. Statistical significance was evaluated using the Students t test.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2279258&req=5

ppat-1000006-g007: Influenza-specific suppressor activity in WT and IL-6βˆ’/βˆ’ mice.Mice were infected i.n. with 20 HAU of influenza virus (H17). Eight weeks after infection, splenocytes from WT and IL6βˆ’/βˆ’ mice were harvested. (A) Purified CD4+ T cells were tested for proliferation against inactivated H17 before (ND) or after (D) depletion of CD25+ T cells. Influenza-specific proliferation in both populations was measured by [3H]-thymidine incorporation at day 5. Each symbol represents an individual mouse and the lines join responses in undepleted (ND) and CD25-depleted (D) CD4+ T cell populations. A stimulation index greater than 2 was considered a positive response. (B) CD4+CD25+ cells from WT and IL-6βˆ’/βˆ’ mice, infected 2 or 8 weeks previously, were isolated from splenocytes and their suppressive capacity was evaluated by incubation at a ratio of 1∢1 with CD4+ T cells from a WT mouse infected 2 weeks previously with H17 influenza virus. The cells were stimulated with either APCs exposed to 1 Β΅g/ml anti-CD3 mAbs (B) or influenza infected APCs (C and D). Proliferation was measured by [3H]-thymidine incorporation at day 5. CD4+CD25+ cells from 4 individual WT and IL-6βˆ’/βˆ’mice were analyzed and each bar represents the mean valueΒ±SEM of each group. Statistical significance was evaluated using the Students t test.
Mentions: Since IL-6 has been shown to abrogate suppression by Tregs [9] and to suppress Treg development by TGFΞ² [10], we postulated that influenza-virus Treg activity would be more readily detectable in IL-6βˆ’/βˆ’ mice than WT mice and that these cells would suppress the activity of virus-specific memory T cells. To test this hypothesis, we first carried out proliferation assays using purified CD4+ T cells depleted of CD25+ cells from both WT and IL-6βˆ’/βˆ’ mice. In this respect, depletion of CD25+ cells had a variable affect on proliferative responses observed in WT mice, removal of CD25+ cells uncovered influenza-specific memory CD4+ T cell responses in the majority of IL-6βˆ’/βˆ’ mice (Figure 7A). This experiment revealed that influenza-specific proliferative responses can be detected in IL-6βˆ’/βˆ’ mice and suggest that these responses, and to a lesser extent, responses in WT mice, are subject to suppression by Tregs. To more closely examine the responsiveness of Tregs in IL-6βˆ’/βˆ’ mice, we performed suppression assays designed to compare 1) Treg activity following polyclonal stimulation of the cells using CD3-specific mAbs (Figure 7B) and 2) influenza-specific Treg activity (Figures 7C and D) in both groups of mice. Suppression assays were carried out using CD4+CD25+ Tregs purified from WT and IL-6βˆ’/βˆ’ mice infected 2 (Figure 7C) and 8 weeks (Figure 7D) previously with influenza virus. CD4+CD25+ T cells derived from these mice were incubated with CD4+CD25βˆ’ T cells from a WT mouse infected two weeks earlier with influenza virus. These T-cell cultures were then stimulated in vitro with either influenza infected APCs or uninfected APCs. Influenza-specific proliferation was measured by [3H]-thymidine incorporation at day 5. As shown in Figures 7C and D, CD4+CD25+ Tregs isolated from IL-6βˆ’/βˆ’, but not WT mice infected 8 weeks (7D) but not 2 weeks (7C) previously with influenza virus, were able to suppress proliferation of WT influenza-specific CD4+ T cells. This data is consistent with our earlier observation that memory but not primary responses are impaired in influenza-infected IL-6βˆ’/βˆ’ mice and further supports the view that IL-6 has an inhibitory effect on the activity of virus-specific Tregs. We were unable to detect a greater increase in the number of Tregs (by Foxp3 staining) in the lymph nodes or spleens of influenza-infected IL-6βˆ’/βˆ’ compared to WT mice. The number of influenza-specific Treg may be very low thus detecting an increase in cell number in the overall Treg population as a result of the influenza virus infection might not be possible. No significant difference was observed in the ability of WT and IL-6βˆ’/βˆ’ CD4+CD25+ Tregs to suppress CD4+CD25βˆ’ T cell proliferation after stimulation with CD3-specific antibodies (Figure 7B) indicating that there is no inherent failure of Tregs to perform immunosuppressive functions in the IL-6βˆ’/βˆ’ mice. Overall, these data clearly indicate that influenza-specific CD4+ T cells, from both WT and IL-6βˆ’/βˆ’ mice, can be suppressed by Tregs, and reveal a crucial role for IL-6 in inhibiting the activity of virus-specific Tregs.

Bottom Line: Specifically, we find that CD4+ but not CD8+ T cell memory is critically dependent upon IL-6.This effect of IL-6 includes its ability to suppress CD4+CD25+ regulatory T cells (Treg).We demonstrate that influenza-induced IL-6 limits the activity of virus-specific Tregs, thereby facilitating the activity of virus-specific memory CD4+ T cells.

View Article: PubMed Central - PubMed

Affiliation: Medical Biochemistry and Immunology, School of Medicine, Cardiff University, Heath Park, Cardiff, United Kingdom.

ABSTRACT
Currently, our understanding of mechanisms underlying cell-mediated immunity and particularly of mechanisms that promote robust T cell memory to respiratory viruses is incomplete. Interleukin (IL)-6 has recently re-emerged as an important regulator of T cell proliferation and survival. Since IL-6 is abundant following infection with influenza virus, we analyzed virus-specific T cell activity in both wild type and IL-6 deficient mice. Studies outlined herein highlight a novel role for IL-6 in the development of T cell memory to influenza virus. Specifically, we find that CD4+ but not CD8+ T cell memory is critically dependent upon IL-6. This effect of IL-6 includes its ability to suppress CD4+CD25+ regulatory T cells (Treg). We demonstrate that influenza-induced IL-6 limits the activity of virus-specific Tregs, thereby facilitating the activity of virus-specific memory CD4+ T cells. These experiments reveal a critical role for IL-6 in ensuring, within the timeframe of an acute infection with a cytopathic virus, that antigen-specific Tregs have no opportunity to down-modulate the immune response, thereby favoring pathogen clearance and survival of the host.

Show MeSH
Related in: MedlinePlus