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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 CD4+ T cell activity in WT and IL-6βˆ’/βˆ’ mice.Proliferation assays were carried out using CD4+ T cells purified from spleens of WT and IL-6βˆ’/βˆ’ mice 2 weeks (A) and 8 weeks (B) post i.n. infection with 20 HAU H17 influenza virus. Effectors were incubated with irradiated WT splenocytes alone or WT splenocytes infected with inactivated H17 influenza or vaccinia virus. [3H]-Thymidine was added on day 5 and proliferation measured by thymidine incorporation after 18 hrs. Mice were analyzed individually and values shown are the meanΒ±SEM (nβ€Š=β€Š3 mice/group). Spleen cells were isolated 8 weeks after primary H17 infection and influenza-specific CD4+ T cells were analyzed for intracellular TNF-Ξ± by flow cytometry (C). Each symbol represents an individual mouse. Kinetic analysis of total CD4+ T cells infiltrated in lungs from WT and IL6βˆ’/βˆ’ mice following primary (D) and secondary (E) i.n. challenge with 20 HAU H17 influenza virus. Mice were analyzed individually and values shown are the meanΒ±SD (nβ€Š=β€Š3 mice/group). Statistical significance was evaluated using the Students t test.
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ppat-1000006-g004: Influenza specific CD4+ T cell activity in WT and IL-6βˆ’/βˆ’ mice.Proliferation assays were carried out using CD4+ T cells purified from spleens of WT and IL-6βˆ’/βˆ’ mice 2 weeks (A) and 8 weeks (B) post i.n. infection with 20 HAU H17 influenza virus. Effectors were incubated with irradiated WT splenocytes alone or WT splenocytes infected with inactivated H17 influenza or vaccinia virus. [3H]-Thymidine was added on day 5 and proliferation measured by thymidine incorporation after 18 hrs. Mice were analyzed individually and values shown are the meanΒ±SEM (nβ€Š=β€Š3 mice/group). Spleen cells were isolated 8 weeks after primary H17 infection and influenza-specific CD4+ T cells were analyzed for intracellular TNF-Ξ± by flow cytometry (C). Each symbol represents an individual mouse. Kinetic analysis of total CD4+ T cells infiltrated in lungs from WT and IL6βˆ’/βˆ’ mice following primary (D) and secondary (E) i.n. challenge with 20 HAU H17 influenza virus. Mice were analyzed individually and values shown are the meanΒ±SD (nβ€Š=β€Š3 mice/group). Statistical significance was evaluated using the Students t test.

Mentions: In light of the ability of IL-6βˆ’/βˆ’ mice to generate a comparable CD8+ T cell response to WT mice, influenza-specific CD4+ T cell responses were also assessed in both groups of mice. Virus-specific proliferation assays using 3H-thymidine incorporation were performed on WT and IL6βˆ’/βˆ’ splenic CD4+ T cells, isolated either 2 weeks post infection (primary CD4+ T cell response), or at 8 weeks following a secondary infection (memory CD4+ T cell response). At 2 weeks post infection no difference was observed in influenza-specific CD4+ T cell proliferation between WT and IL6βˆ’/βˆ’ mice, with both groups exhibiting robust virus-specific responses (Figure 4A). However, at 8 weeks post infection, the difference between the two mouse strains was striking. Whilst virus-specific proliferation was readily observed in WT mice, a notable reduction in proliferation was observed in IL6βˆ’/βˆ’ mice (Figure 4B), indicating that influenza-specific memory CD4+ T cell responses are severely impaired in the absence of IL-6. In further support of this, we found that whilst TNFΞ±-producing CD4+ T cells could be observed following a 5 hour in vitro restimulation of CD4+ T cells isolated from the spleens of WT mice infected 8 weeks previously with influenza virus, these cells were not observed following restimulation of CD4+ T cells purified from IL-6βˆ’/βˆ’ mice (Figure 4C). Collectively these data imply that the activity of influenza-specific central memory T-cells (TCM cells, which retain proliferative capacity after initial antigen challenge) and effector memory T cells (TEM, which produce cytokines rapidly upon re-exposure to antigen) are both impaired in IL-6βˆ’/βˆ’ mice. To extend these observations, we assessed CD4+ T cell responses ex vivo by measuring the presence of CD4+ T cells in the lungs of both WT and IL-6βˆ’/βˆ’ mice following the first and second exposure to influenza virus. For this purpose, WT and IL6βˆ’/βˆ’ mice were initially infected (i.n) with influenza virus and then subsequently re-infected by the same route 8 weeks later. CD4+ T cell numbers in the lungs were then recorded during the first 2–12 days of the first (Figure 4D) and second infection (Figure 4E). Although both WT and IL-6βˆ’/βˆ’ mice elicited primary responses to influenza infection, the overall profile of CD4+ T cell infiltrating of the lung indicates that the T cell response was slightly delayed in IL-6βˆ’/βˆ’ mice consistent with previous reports (Figure 4D) [7]. These differences were however more pronounced following the second viral challenge (Figure 4E). In this respect, the number of CD4+ T cells in the lungs was dramatically reduced in IL-6βˆ’/βˆ’ mice as compared to WT mice. Whilst a defect in trafficking may contribute to this reduction in T cell number, the results are also consistent with a profound failure of the influenza-specific CD4+ T cell memory response detailed in Figures 4B and C above.


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 CD4+ T cell activity in WT and IL-6βˆ’/βˆ’ mice.Proliferation assays were carried out using CD4+ T cells purified from spleens of WT and IL-6βˆ’/βˆ’ mice 2 weeks (A) and 8 weeks (B) post i.n. infection with 20 HAU H17 influenza virus. Effectors were incubated with irradiated WT splenocytes alone or WT splenocytes infected with inactivated H17 influenza or vaccinia virus. [3H]-Thymidine was added on day 5 and proliferation measured by thymidine incorporation after 18 hrs. Mice were analyzed individually and values shown are the meanΒ±SEM (nβ€Š=β€Š3 mice/group). Spleen cells were isolated 8 weeks after primary H17 infection and influenza-specific CD4+ T cells were analyzed for intracellular TNF-Ξ± by flow cytometry (C). Each symbol represents an individual mouse. Kinetic analysis of total CD4+ T cells infiltrated in lungs from WT and IL6βˆ’/βˆ’ mice following primary (D) and secondary (E) i.n. challenge with 20 HAU H17 influenza virus. Mice were analyzed individually and values shown are the meanΒ±SD (nβ€Š=β€Š3 mice/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-g004: Influenza specific CD4+ T cell activity in WT and IL-6βˆ’/βˆ’ mice.Proliferation assays were carried out using CD4+ T cells purified from spleens of WT and IL-6βˆ’/βˆ’ mice 2 weeks (A) and 8 weeks (B) post i.n. infection with 20 HAU H17 influenza virus. Effectors were incubated with irradiated WT splenocytes alone or WT splenocytes infected with inactivated H17 influenza or vaccinia virus. [3H]-Thymidine was added on day 5 and proliferation measured by thymidine incorporation after 18 hrs. Mice were analyzed individually and values shown are the meanΒ±SEM (nβ€Š=β€Š3 mice/group). Spleen cells were isolated 8 weeks after primary H17 infection and influenza-specific CD4+ T cells were analyzed for intracellular TNF-Ξ± by flow cytometry (C). Each symbol represents an individual mouse. Kinetic analysis of total CD4+ T cells infiltrated in lungs from WT and IL6βˆ’/βˆ’ mice following primary (D) and secondary (E) i.n. challenge with 20 HAU H17 influenza virus. Mice were analyzed individually and values shown are the meanΒ±SD (nβ€Š=β€Š3 mice/group). Statistical significance was evaluated using the Students t test.
Mentions: In light of the ability of IL-6βˆ’/βˆ’ mice to generate a comparable CD8+ T cell response to WT mice, influenza-specific CD4+ T cell responses were also assessed in both groups of mice. Virus-specific proliferation assays using 3H-thymidine incorporation were performed on WT and IL6βˆ’/βˆ’ splenic CD4+ T cells, isolated either 2 weeks post infection (primary CD4+ T cell response), or at 8 weeks following a secondary infection (memory CD4+ T cell response). At 2 weeks post infection no difference was observed in influenza-specific CD4+ T cell proliferation between WT and IL6βˆ’/βˆ’ mice, with both groups exhibiting robust virus-specific responses (Figure 4A). However, at 8 weeks post infection, the difference between the two mouse strains was striking. Whilst virus-specific proliferation was readily observed in WT mice, a notable reduction in proliferation was observed in IL6βˆ’/βˆ’ mice (Figure 4B), indicating that influenza-specific memory CD4+ T cell responses are severely impaired in the absence of IL-6. In further support of this, we found that whilst TNFΞ±-producing CD4+ T cells could be observed following a 5 hour in vitro restimulation of CD4+ T cells isolated from the spleens of WT mice infected 8 weeks previously with influenza virus, these cells were not observed following restimulation of CD4+ T cells purified from IL-6βˆ’/βˆ’ mice (Figure 4C). Collectively these data imply that the activity of influenza-specific central memory T-cells (TCM cells, which retain proliferative capacity after initial antigen challenge) and effector memory T cells (TEM, which produce cytokines rapidly upon re-exposure to antigen) are both impaired in IL-6βˆ’/βˆ’ mice. To extend these observations, we assessed CD4+ T cell responses ex vivo by measuring the presence of CD4+ T cells in the lungs of both WT and IL-6βˆ’/βˆ’ mice following the first and second exposure to influenza virus. For this purpose, WT and IL6βˆ’/βˆ’ mice were initially infected (i.n) with influenza virus and then subsequently re-infected by the same route 8 weeks later. CD4+ T cell numbers in the lungs were then recorded during the first 2–12 days of the first (Figure 4D) and second infection (Figure 4E). Although both WT and IL-6βˆ’/βˆ’ mice elicited primary responses to influenza infection, the overall profile of CD4+ T cell infiltrating of the lung indicates that the T cell response was slightly delayed in IL-6βˆ’/βˆ’ mice consistent with previous reports (Figure 4D) [7]. These differences were however more pronounced following the second viral challenge (Figure 4E). In this respect, the number of CD4+ T cells in the lungs was dramatically reduced in IL-6βˆ’/βˆ’ mice as compared to WT mice. Whilst a defect in trafficking may contribute to this reduction in T cell number, the results are also consistent with a profound failure of the influenza-specific CD4+ T cell memory response detailed in Figures 4B and C above.

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