Tregs restrain dendritic cell autophagy to ameliorate autoimmunity
Themis Alissafi ... Ken Cadwell, Panayotis Verginis
Themis Alissafi ... Ken Cadwell, Panayotis Verginis
Published June 30, 2017
Citation Information: J Clin Invest. 2017;127(7):2789-2804. doi:10.1172/JCI92079.
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Categories: Research Article Autoimmunity Immunology

Tregs restrain dendritic cell autophagy to ameliorate autoimmunity

Abstract

Design of efficacious Treg-based therapies and establishment of clinical tolerance in autoimmune diseases have proven to be challenging. The clinical implementation of Treg immunotherapy has been hampered by various impediments related to the stability and isolation procedures of Tregs as well as the specific in vivo targets of Treg modalities. Herein, we have demonstrated that Foxp3+ Tregs potently suppress autoimmune responses in vivo through inhibition of the autophagic machinery in DCs in a cytotoxic T-lymphocyte–associated protein 4–dependent (CTLA4-dependent) manner. Autophagy-deficient DCs exhibited reduced immunogenic potential and failed to prime autoantigen-specific CD4+ T cells to mediate autoimmunity. Mechanistically, CTLA4 binding promoted activation of the PI3K/Akt/mTOR axis and FoxO1 nuclear exclusion in DCs, leading to decreased transcription of the autophagy component microtubule-associated protein 1 light chain 3β (Lc3b). Human DCs treated with CTLA4-Ig, a fusion protein composed of the Fc region of IgG1 and the extracellular domain of CTLA4 (also known as abatacept, marketed as Orencia), demonstrated reduced levels of autophagosome formation, while DCs from CTLA4-Ig–treated rheumatoid arthritis patients displayed diminished LC3B transcripts. Collectively, our data identify the canonical autophagy pathway in DCs as a molecular target of Foxp3+ Treg–mediated suppression that leads to amelioration of autoimmune responses. These findings may pave the way for the development of therapeutic protocols that exploit Tregs for the treatment of autoimmunity as well as diseases in which disturbed tolerance is a common denominator.

Authors

Themis Alissafi, Aggelos Banos, Louis Boon, Tim Sparwasser, Alessandra Ghigo, Kajsa Wing, Dimitrios Vassilopoulos, Dimitrios Boumpas, Triantafyllos Chavakis, Ken Cadwell, Panayotis Verginis

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Foxp3+ Treg–mediated tolerance regulates autophagy in DCs. (A) Hierarchi...

Figure 1

Foxp3+ Treg–mediated tolerance regulates autophagy in DCs.

(A) Hierarchical clustering of autophagy-related genes upon transcriptomic analysis of sorted DCs from control (n = 2) and tolerized (n = 3) mice. (B) Relative mRNA expression of Atg5 and Atg16l1 in DCs from control, tolerized, and tolerized Foxp3+ Treg–depleted mice. Results are expressed as mean ± SEM. n = 6 mice per group, 3 independent experiments. *P = 0.0389; †P = 0.0147; ‡P = 0.0145; §P = 0.0241. (C) Western blot analysis for expression of LC3, p62, and actin in DC lysates of indicated groups. Protein extract from Neuro 2A cell line was used as control. One representative experiment of 4 is depicted. Relative intensity of LC3II/LC3I and p62 are depicted. Results are expressed as mean ± SEM. n = 6 mice per group, 3 independent experiments. *P = 0.0184; †P = 0.05; ‡P = 0.0432. (D) Immunofluorescence confocal microscopy for LC3 (red), LAMP-1 (green), p62 (silver white), and DAPI (blue) in DCs. Representative fields at 2 different magnifications are depicted. Scale bars: 5 μm. One representative experiment of 3 is shown. n = 4 mice per group. LC3 puncta/cell and p62 puncta/cell are depicted. ***P < 0.0001; **P = 0.0003. Results are expressed as mean ± SEM. n = 4 mice per group, 3 independent experiments. For A–D, DCs were isolated from dLNs and spleens of mice at 3.5 days after immunization. Statistical significance was obtained by 2-way ANOVA.