Treg activation during allograft tolerance induction requires mitochondrion-induced TGF-β1 in type 1 conventional dendritic cells
Samantha L. Schroth, Lei Zhang, Rebecca T.L. Jones, Kristofor Glinton, Nikita L. Mani, Hiroyasu Inui, Jesse T. Davidson, Samuel E. Weinberg, Navdeep S. Chandel, Maria-Luisa Alegre, Edward B. Thorp
Samantha L. Schroth, Lei Zhang, Rebecca T.L. Jones, Kristofor Glinton, Nikita L. Mani, Hiroyasu Inui, Jesse T. Davidson, Samuel E. Weinberg, Navdeep S. Chandel, Maria-Luisa Alegre, Edward B. Thorp
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Research Article Immunology

Treg activation during allograft tolerance induction requires mitochondrion-induced TGF-β1 in type 1 conventional dendritic cells

Abstract

The role of conventional type 1 DCs (cDC1s) in tolerance induction to solid organ allografts is unknown and important for strategies that seek to prolong allograft viability. Using a murine model deficient in cDC1s, we report cDC1s are required for donor antigen and costimulation blockade (DST + CoB) tolerance induction and survival of cardiac allografts. cDC1 deficiency led to decreases in CD4+CD25+FoxP3+ T cells within allograft and spleen tissue of transplant recipients, and this was found to be antigen specific. Donor antigen stimulation induced TGF-β1 expression in both in vivo cDC1s and in vitro Flt3L-derived cDC1s. Genetic deletion of TGF-β1 in cDC1s prevented induction of antigen-specific CD4+CD25+FoxP3+ T cells and was associated with cardiac allograft rejection. In parallel, single-cell RNA sequencing and metabolic analysis revealed upregulation of cDC1 mitochondrial metabolic signatures after in vivo exposure to DST + CoB. Genetic inactivation of cDC1 mitochondrial metabolism reduced expression of cDC1 TGF-β1, decreased antigen-specific Treg populations, and impaired allograft tolerance. Taken together, our findings implicate cDC1s in strategies to preserve solid organ allografts and also implicate mitochondrial metabolism of cDC1s as a molecular mechanism to enhance the generation of antigen-specific CD4+CD25+FoxP3+ T cells through TGF-β1.

Authors

Samantha L. Schroth, Lei Zhang, Rebecca T.L. Jones, Kristofor Glinton, Nikita L. Mani, Hiroyasu Inui, Jesse T. Davidson, Samuel E. Weinberg, Navdeep S. Chandel, Maria-Luisa Alegre, Edward B. Thorp

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Figure 5

cDC1-expressed TGF-β1 is necessary for induction of antigen-specific CD25+FoxP3+ T cells.

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cDC1-expressed TGF-β1 is necessary for induction of antigen-specific CD2...
(A) Antigen-specific persistent antigen simulation experimental scheme whereby TGF-β1fl/fl and Xcr1Cre/+TGF-β1fl/fl mice were injected (i.v.) with CD90.1+ OTII T cells on day –1 and treated with ova DST + CoB infusion (i.v.) on day 0, followed by ova DST injections (i.p.) on days 2, 4, and 6 before collection of spleens on day 7. (B) Flow cytometry gating strategy for identification of splenic antigen-specific congenic CD90.1+ OTII cells from the spleens of ova DST + CoB–treated mice. (C) Quantification of endogenous splenic CD3+, CD4+, and CD4+CD25+FoxP3+ T cells. n = 5–6 per group. Determined no significance (ns) by 1-way ANOVA followed by Tukey’s test. (D) Quantification of splenic CD90.1+ OTII T cells 7 days after ova DST + CoB and persistent ova antigen treatment. n = 5–6 per group. Determined no significance (ns) by 2-tailed unpaired t test. (E) Quantification of splenic CD90.1+ OTII CD25+FoxP3+ T cells. Data shown as cells/mg splenic tissue and as the percentage of OTII cell population. n = 5–6 per group. *P < 0.05, **P < 0.01 by 2-tailed unpaired t test. (F) Representative flow plots of OTII CD25+FoxP3+ T cells in spleens of persistent antigen-treated TGF-β1fl/fl and Xcr1Cre/+TGF-β1fl/fl mice. Cells were pre-gated as live single CD90.1+ TCRVβ5.1+ cells. FMO, fluorescence minus one.