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 3

cDC1s are necessary for induction of splenic CD25+FoxP3+ T cells after DST + CoB.

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cDC1s are necessary for induction of splenic CD25+FoxP3+ T cells after D...
(A) Persistent antigen stimulation experimental scheme whereby B6 and cDC1-KO mice were treated with CD45.1+ BALB/c DST + CoB infusion on day 0 (i.v.), followed by CD45.1+ BALB/c DST injections (i.p.) on days 2, 4, and 6 before collection of spleens on day 7. (B) Quantification of CD45.1– adaptive immune cell populations (CD3+ or CD19+) in spleens of naive and persistent antigen-treated B6 or cDC1-KO mice. n = 4–5 per group. *P < 0.05 by 1-way ANOVA with Tukey’s test followed by Tukey’s test. (C) Flow cytometry gating strategy for CD45.1–CD4+CD25+FoxP3+ T cell identification in spleens of B6 and cDC1-KO mice. (D) Quantification of CD45.1–CD8+ and CD45.1–CD4+ T cell populations in spleens of naive and persistent antigen-treated B6 or cDC1-KO mice. n = 4–5 per group. *P < 0.05, **P < 0.01 by 1-way ANOVA followed by Tukey’s test. (E) Quantification of CD4+FoxP3+ and CD4+CD25+FoxP3+ T cells in spleens of naive and persistent antigen-treated B6 or cDC1-KO mice. Cells were pre-gated as live single CD3+ CD4+ CD45.1– cells. Data shown as cells/mg splenic tissue and as the percentage of CD4+FoxP3+ cell population. n = 4–5 per group. *P < 0.05, **P < 0.01 by 1-way ANOVA followed by Tukey’s test. (F) Congenic transfer of CD90.1+ OT-II CD4 T cells into B6 and cDC1-KO mice on day –1 followed by persistent membrane-bound ova + CoB and persistent ova antigen stimulation. Representative gating and flow plots of CD3+CD90.1+CD25+FoxP3+ OTII T cells specific to ova antigen in B6 versus cDC1-KO spleens. Cells were pre-gated as live single CD3+ CD90.1+ cells. (G) Quantification of CD90.1+FoxP3+ OTII and CD90.1+CD25+FoxP3+ OTII T cells in B6 or cDC1-KO mice after ova + CoB and persistent ova antigen stimulation. n = 5 per group. *P < 0.05 by 2-tailed unpaired t test.