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Autophagy is a critical regulator of memory CD8(+) T cell formation.

Puleston DJ, Zhang H, Powell TJ, Lipina E, Sims S, Panse I, Watson AS, Cerundolo V, Townsend AR, Klenerman P, Simon AK - Elife (2014)

Bottom Line: Autophagy is a major cellular lysosomal degradation pathway of bulk material, and levels are known to fall with age.In this study, we describe a novel role for autophagy in CD8(+) T cell memory formation.This study reveals a cell intrinsic explanation for poor CD8(+) T cell memory in the elderly and potentially offers novel immune modulators to improve aged immunity.

View Article: PubMed Central - PubMed

Affiliation: MRC Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom.

ABSTRACT
During infection, CD8(+) T cells initially expand then contract, leaving a small memory pool providing long lasting immunity. While it has been described that CD8(+) T cell memory formation becomes defective in old age, the cellular mechanism is largely unknown. Autophagy is a major cellular lysosomal degradation pathway of bulk material, and levels are known to fall with age. In this study, we describe a novel role for autophagy in CD8(+) T cell memory formation. Mice lacking the autophagy gene Atg7 in T cells failed to establish CD8(+) T cell memory to influenza and MCMV infection. Interestingly, autophagy levels were diminished in CD8(+) T cells from aged mice. We could rejuvenate CD8(+) T cell responses in elderly mice in an autophagy dependent manner using the compound spermidine. This study reveals a cell intrinsic explanation for poor CD8(+) T cell memory in the elderly and potentially offers novel immune modulators to improve aged immunity.

No MeSH data available.


Related in: MedlinePlus

The T cell phenotype of Vav-Atg5−/− mice is similar to that of T-Atg7−/− mice and the survival defect of Atg7−/− CD8+ T cells is cell intrinsic.(A) Flow cytometric analysis of CD4+ and CD8+ T cell frequencies in the spleen of WT and Vav-Atg5−/− mice. Quantitative analyses are representative of two independent experiments, **p < 0.01 (n = 5). (B) Frequency of CD44hi cells within the CD8+ T cell subset of WT and Vav-Atg5−/− mice. Data are representative of two independent experiments, **p < 0.01 (n = 5). (C) BM reconstitution in BM chimera mice. 9 weeks after marrow transplantation, the frequency of donor CD45.2 cells was assessed in the spleen by flow cytometry. Quantified is the frequency of splenocytes expressing CD45.2 in BM chimera mice and in normal WT and T-Atg7−/− mice that acted as controls. (D) Frequency of CD8+ T cells that are CD45.2 donor-derived in BM chimera mice. Example dot plots are gated on CD8+ T cells. Quantified is the frequency of CD8+ T cells that express CD45.2 in BM chimera and in normal WT and T-Atg7−/− mice that acted as controls. *p < 0.05 (n = 4). Data are mean ± s.e.m and all statistical analyses are Mann–Whitney U-tests.DOI:http://dx.doi.org/10.7554/eLife.03706.005
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fig1s2: The T cell phenotype of Vav-Atg5−/− mice is similar to that of T-Atg7−/− mice and the survival defect of Atg7−/− CD8+ T cells is cell intrinsic.(A) Flow cytometric analysis of CD4+ and CD8+ T cell frequencies in the spleen of WT and Vav-Atg5−/− mice. Quantitative analyses are representative of two independent experiments, **p < 0.01 (n = 5). (B) Frequency of CD44hi cells within the CD8+ T cell subset of WT and Vav-Atg5−/− mice. Data are representative of two independent experiments, **p < 0.01 (n = 5). (C) BM reconstitution in BM chimera mice. 9 weeks after marrow transplantation, the frequency of donor CD45.2 cells was assessed in the spleen by flow cytometry. Quantified is the frequency of splenocytes expressing CD45.2 in BM chimera mice and in normal WT and T-Atg7−/− mice that acted as controls. (D) Frequency of CD8+ T cells that are CD45.2 donor-derived in BM chimera mice. Example dot plots are gated on CD8+ T cells. Quantified is the frequency of CD8+ T cells that express CD45.2 in BM chimera and in normal WT and T-Atg7−/− mice that acted as controls. *p < 0.05 (n = 4). Data are mean ± s.e.m and all statistical analyses are Mann–Whitney U-tests.DOI:http://dx.doi.org/10.7554/eLife.03706.005

Mentions: Previous reports have noted a number of changes to the naïve CD8+ T cell compartment in the absence of autophagy, with T cell lymphopenia, a consistent observation (Pua et al., 2007; Puleston and Simon, 2014). We set out to investigate if an altered naïve CD8+ T cell compartment exists in T-Atg7−/− mice. We confirmed observations from previous reports using similar autophagy-deficient mouse models (Pua et al., 2007, 2009) that thymic development of CD4+ and CD8+ T cells was normal in 6-week old T-Atg7−/− mice (Figure 1A). However, mice were lymphopenic for both CD4+ and CD8+ T cells in the lymph nodes and blood (Figure 1B,C). Moreover, Atg7−/− CD8+ T cells exhibited an activated phenotype with increased CD44 expression (Figure 1D) and decreased CD62L expression (Figure 1E), resembling a ‘virtual memory’ compartment (Akue et al., 2012). We observed similar frequencies of central effector memory CD62L+CD44hi, however, T-Atg7−/− mice accumulated CD8+ T cells with an effector memory phenotype (CD62L−CD44hi) (Figure 1—figure supplement 1E). Similarly, data from a mouse model in which another essential autophagy gene, Atg5, was deleted under the hematopoietic stem cell-specific promoter Vav, showed T cell lymphopenia and the expanded virtual memory T cell compartment (CD8+CD44+) suggesting this phenotype is not Atg7 specific (Figure 1—figure supplement 2A and B). Next, we established that proliferation was increased in the activated CD44hi CD8+ T cell compartment by Ki-67 staining (Figure 1F). The observed activated phenotype and increased cell turnover in Atg7−/− CD8+ T cells are likely driven by homeostatic proliferation in an attempt to fill the depleted T cell niche. Indeed, the expression of the homeostatic proliferation marker CD24 (Li et al., 2006) was found to be significantly increased on Atg7−/− CD8+ T cells (Figure 1G). To investigate whether lymphopenia drives this activated phenotype in the CD8+ T cell compartment, we generated 1:1 mixed bone marrow (BM) chimeras from CD45.2+ T-Atg7−/− BM mixed with CD45.1+ wild-type BM. Both BMs contributed equally to form the new hematological system (Figure 1—figure supplement 2C). Atg7−/− CD8+ T cells were still diminished even in the presence of a replete T cell niche, suggesting the survival defect previously described for autophagy-deficient T cells (Pua et al., 2007; Mortensen et al., 2010) is cell-intrinsic (Figure 1—figure supplement 2D). However, the activated Atg7−/− CD8+ T cell phenotype was no longer detected in BM chimeras as measured by the frequency of donor CD45.2+ CD8+ T cells found to be CD62L+ (Figure 1H) and CD44hi (Figure 1I). These data indicate that the observed homeostatic proliferation and the change in surface phenotype of Atg7−/− CD8+ T cells are driven by lymphopenia and are not cell-intrinsic.10.7554/eLife.03706.003Figure 1.Lymphopenia induces homeostatic proliferation and an activated CD8+ T cell phenotype in T-Atg7−/− mice.


Autophagy is a critical regulator of memory CD8(+) T cell formation.

Puleston DJ, Zhang H, Powell TJ, Lipina E, Sims S, Panse I, Watson AS, Cerundolo V, Townsend AR, Klenerman P, Simon AK - Elife (2014)

The T cell phenotype of Vav-Atg5−/− mice is similar to that of T-Atg7−/− mice and the survival defect of Atg7−/− CD8+ T cells is cell intrinsic.(A) Flow cytometric analysis of CD4+ and CD8+ T cell frequencies in the spleen of WT and Vav-Atg5−/− mice. Quantitative analyses are representative of two independent experiments, **p < 0.01 (n = 5). (B) Frequency of CD44hi cells within the CD8+ T cell subset of WT and Vav-Atg5−/− mice. Data are representative of two independent experiments, **p < 0.01 (n = 5). (C) BM reconstitution in BM chimera mice. 9 weeks after marrow transplantation, the frequency of donor CD45.2 cells was assessed in the spleen by flow cytometry. Quantified is the frequency of splenocytes expressing CD45.2 in BM chimera mice and in normal WT and T-Atg7−/− mice that acted as controls. (D) Frequency of CD8+ T cells that are CD45.2 donor-derived in BM chimera mice. Example dot plots are gated on CD8+ T cells. Quantified is the frequency of CD8+ T cells that express CD45.2 in BM chimera and in normal WT and T-Atg7−/− mice that acted as controls. *p < 0.05 (n = 4). Data are mean ± s.e.m and all statistical analyses are Mann–Whitney U-tests.DOI:http://dx.doi.org/10.7554/eLife.03706.005
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fig1s2: The T cell phenotype of Vav-Atg5−/− mice is similar to that of T-Atg7−/− mice and the survival defect of Atg7−/− CD8+ T cells is cell intrinsic.(A) Flow cytometric analysis of CD4+ and CD8+ T cell frequencies in the spleen of WT and Vav-Atg5−/− mice. Quantitative analyses are representative of two independent experiments, **p < 0.01 (n = 5). (B) Frequency of CD44hi cells within the CD8+ T cell subset of WT and Vav-Atg5−/− mice. Data are representative of two independent experiments, **p < 0.01 (n = 5). (C) BM reconstitution in BM chimera mice. 9 weeks after marrow transplantation, the frequency of donor CD45.2 cells was assessed in the spleen by flow cytometry. Quantified is the frequency of splenocytes expressing CD45.2 in BM chimera mice and in normal WT and T-Atg7−/− mice that acted as controls. (D) Frequency of CD8+ T cells that are CD45.2 donor-derived in BM chimera mice. Example dot plots are gated on CD8+ T cells. Quantified is the frequency of CD8+ T cells that express CD45.2 in BM chimera and in normal WT and T-Atg7−/− mice that acted as controls. *p < 0.05 (n = 4). Data are mean ± s.e.m and all statistical analyses are Mann–Whitney U-tests.DOI:http://dx.doi.org/10.7554/eLife.03706.005
Mentions: Previous reports have noted a number of changes to the naïve CD8+ T cell compartment in the absence of autophagy, with T cell lymphopenia, a consistent observation (Pua et al., 2007; Puleston and Simon, 2014). We set out to investigate if an altered naïve CD8+ T cell compartment exists in T-Atg7−/− mice. We confirmed observations from previous reports using similar autophagy-deficient mouse models (Pua et al., 2007, 2009) that thymic development of CD4+ and CD8+ T cells was normal in 6-week old T-Atg7−/− mice (Figure 1A). However, mice were lymphopenic for both CD4+ and CD8+ T cells in the lymph nodes and blood (Figure 1B,C). Moreover, Atg7−/− CD8+ T cells exhibited an activated phenotype with increased CD44 expression (Figure 1D) and decreased CD62L expression (Figure 1E), resembling a ‘virtual memory’ compartment (Akue et al., 2012). We observed similar frequencies of central effector memory CD62L+CD44hi, however, T-Atg7−/− mice accumulated CD8+ T cells with an effector memory phenotype (CD62L−CD44hi) (Figure 1—figure supplement 1E). Similarly, data from a mouse model in which another essential autophagy gene, Atg5, was deleted under the hematopoietic stem cell-specific promoter Vav, showed T cell lymphopenia and the expanded virtual memory T cell compartment (CD8+CD44+) suggesting this phenotype is not Atg7 specific (Figure 1—figure supplement 2A and B). Next, we established that proliferation was increased in the activated CD44hi CD8+ T cell compartment by Ki-67 staining (Figure 1F). The observed activated phenotype and increased cell turnover in Atg7−/− CD8+ T cells are likely driven by homeostatic proliferation in an attempt to fill the depleted T cell niche. Indeed, the expression of the homeostatic proliferation marker CD24 (Li et al., 2006) was found to be significantly increased on Atg7−/− CD8+ T cells (Figure 1G). To investigate whether lymphopenia drives this activated phenotype in the CD8+ T cell compartment, we generated 1:1 mixed bone marrow (BM) chimeras from CD45.2+ T-Atg7−/− BM mixed with CD45.1+ wild-type BM. Both BMs contributed equally to form the new hematological system (Figure 1—figure supplement 2C). Atg7−/− CD8+ T cells were still diminished even in the presence of a replete T cell niche, suggesting the survival defect previously described for autophagy-deficient T cells (Pua et al., 2007; Mortensen et al., 2010) is cell-intrinsic (Figure 1—figure supplement 2D). However, the activated Atg7−/− CD8+ T cell phenotype was no longer detected in BM chimeras as measured by the frequency of donor CD45.2+ CD8+ T cells found to be CD62L+ (Figure 1H) and CD44hi (Figure 1I). These data indicate that the observed homeostatic proliferation and the change in surface phenotype of Atg7−/− CD8+ T cells are driven by lymphopenia and are not cell-intrinsic.10.7554/eLife.03706.003Figure 1.Lymphopenia induces homeostatic proliferation and an activated CD8+ T cell phenotype in T-Atg7−/− mice.

Bottom Line: Autophagy is a major cellular lysosomal degradation pathway of bulk material, and levels are known to fall with age.In this study, we describe a novel role for autophagy in CD8(+) T cell memory formation.This study reveals a cell intrinsic explanation for poor CD8(+) T cell memory in the elderly and potentially offers novel immune modulators to improve aged immunity.

View Article: PubMed Central - PubMed

Affiliation: MRC Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom.

ABSTRACT
During infection, CD8(+) T cells initially expand then contract, leaving a small memory pool providing long lasting immunity. While it has been described that CD8(+) T cell memory formation becomes defective in old age, the cellular mechanism is largely unknown. Autophagy is a major cellular lysosomal degradation pathway of bulk material, and levels are known to fall with age. In this study, we describe a novel role for autophagy in CD8(+) T cell memory formation. Mice lacking the autophagy gene Atg7 in T cells failed to establish CD8(+) T cell memory to influenza and MCMV infection. Interestingly, autophagy levels were diminished in CD8(+) T cells from aged mice. We could rejuvenate CD8(+) T cell responses in elderly mice in an autophagy dependent manner using the compound spermidine. This study reveals a cell intrinsic explanation for poor CD8(+) T cell memory in the elderly and potentially offers novel immune modulators to improve aged immunity.

No MeSH data available.


Related in: MedlinePlus