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CD4 T cell autophagy is integral to memory maintenance.

ABSTRACT: Studies of mice deficient for autophagy in T cells since thymic development, concluded that autophagy is integral to mature T cell homeostasis. Basal survival and functional impairments in vivo, limited the use of these models to delineate the role of autophagy during the immune response. We generated Atg5 ^f/f distal Lck (dLck)-cre mice, with deletion of autophagy only at a mature stage. In this model, autophagy deficiency impacts CD8⁺ T cell survival but has no influence on CD4⁺ T cell number and short-term activation. Moreover, autophagy in T cells is dispensable during early humoral response but critical for long-term antibody production. Autophagy in CD4⁺ T cells is required to transfer humoral memory as shown by injection of antigen-experienced cells in naive mice. We also observed a selection of autophagy-competent cells in the CD4⁺ T cell memory compartment. We performed in vitro differentiation of memory CD4⁺ T cells, to better characterize autophagy-deficient memory cells. We identified mitochondrial and lipid load defects in differentiated memory CD4⁺ T cells, together with a compromised survival, without any collapse of energy production. We then propose that memory CD4⁺ T cells rely on autophagy for their survival to regulate toxic effects of mitochondrial activity and lipid overload.

SUBMITTER: Murera D

PROVIDER: S-EPMC5899169 | biostudies-literature | 2018 Apr

REPOSITORIES: biostudies-literature

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CD4 T cell autophagy is integral to memory maintenance.

Murera Diane D Arbogast Florent F Arnold Johan J Bouis Delphine D Muller Sylviane S Gros Frédéric F

Scientific reports 20180413 1

Studies of mice deficient for autophagy in T cells since thymic development, concluded that autophagy is integral to mature T cell homeostasis. Basal survival and functional impairments in vivo, limited the use of these models to delineate the role of autophagy during the immune response. We generated Atg5 <sup>f/f</sup> distal Lck (dLck)-cre mice, with deletion of autophagy only at a mature stage. In this model, autophagy deficiency impacts CD8<sup>+</sup> T cell survival but has no influence o ...[more]

PMID: 29654322

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Project description:Protection at the peak of Plasmodium chabaudi blood-stage malaria infection is provided by CD4 T cells. We have shown that an increase in Th1 cells also correlates with protection during the persistent phase of malaria; however, it is unclear how these T cells are maintained. Persistent malaria infection promotes protection and generates both effector T cells (Teff), and effector memory T cells (Tem). We have previously defined new CD4 Teff (IL-7R?-) subsets from Early (TeffEarly, CD62LhiCD27+) to Late (TeffLate, CD62LloCD27-) activation states. Here, we tested these effector and memory T cell subsets for their ability to survive and protect in vivo. We found that both polyclonal and P. chabaudi Merozoite Surface Protein-1 (MSP-1)-specific B5 TCR transgenic Tem survive better than Teff. Surprisingly, as Tem are associated with antigen persistence, Tem survive well even after clearance of infection. As previously shown during T cell contraction, TeffEarly, which can generate Tem, also survive better than other Teff subsets in uninfected recipients. Two other Tem survival mechanisms identified here are that low-level chronic infection promotes Tem both by driving their proliferation, and by programming production of Tem from Tcm. Protective CD4 T cell phenotypes have not been precisely determined in malaria, or other persistent infections. Therefore, we tested purified memory (Tmem) and Teff subsets in protection from peak pathology and parasitemia in immunocompromised recipient mice. Strikingly, among Tmem (IL-7R?hi) subsets, only TemLate (CD62LloCD27-) reduced peak parasitemia (19%), though the dominant memory subset is TemEarly, which is not protective. In contrast, all Teff subsets reduced peak parasitemia by more than half, and mature Teff can generate Tem, though less. In summary, we have elucidated four mechanisms of Tem maintenance, and identified two long-lived T cell subsets (TemLate, TeffEarly) that may represent correlates of protection or a target for longer-lived vaccine-induced protection against malaria blood-stages.

Project description:IntroductionRituximab (RTX) is a B cell-depleting agent approved for the treatment of granulomatosis with polyangiitis (GPA). RTX reduces antibody producing precursor plasma cells and inhibits B and T cells interaction. Infections related to T cell immunodeficiency are not infrequent during RTX treatment. Our study investigated CD4 cell count and CD4/CD8 ratio in GPA patients during the first two years of long-term RTX treatment.MethodsA single centre cohort study of 35 patients who received median total cumulative dose of cyclophosphamide (CYC) of 15 g and were treated with RTX 2 g followed by retreatment with either 2 g once annually or 1 g biannually. Serum levels of total immunoglobulin (Ig) and lymphocytes subsets were recorded at RTX initiation and at 3, 6, 12, 18 and 24 months. Low CD4 count and inverted CD4/CD8 ratio were defined as CD4 < 0.3 × 10(9)/l and ratio < 1.ResultsThe CD4 cell count and CD4/CD8 ratio decreased slightly following the initial RTX treatment and then increased gradually during maintenance treatment. While the proportion of patients with low CD4 cell count decreased from 43% at baseline to 18% at 24 months, the ratio remained inverted in 40%. Oral daily prednisolone dose at baseline, CYC exposure and the maintenance regimen did not influence the CD4 cell count and ratio. Being older (p = 0.012) and having a higher CRP (p = 0.044) and ESR (p = 0.024) at baseline significantly increased the risk of inverted CD4/CD8 ratio at 24 months. Inverted ratio at baseline associated with lower total Ig levels during the study.ConclusionsOverall, the CD4 and CD4/CD8 ratio increased during maintenance RTX therapy in GPA with no discernible impact of other immunosuppressive therapy. However the increase in CD4 was not followed by an increase in the CD4/CD8 ratio, especially in older patients. Inverted CD4/CD8 ratio associated with lower Ig levels, suggesting a more profound B cell depleting effect of RTX with a relative increase in CD8+ lymphocytes.

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CD4 T cell autophagy is integral to memory maintenance.

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CD4 T cell autophagy is integral to memory maintenance.

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