Biology subjects

Graff-Dubois, S.

Publications and source records attributed to Graff-Dubois, S..

6 recordsLinked to original sources

bioRxiv2026

Type 1 and type 2 dendritic cell subsets cooperate to maintain intestinal immune tolerance via integrin αvβ8-mediated TGF-β activation

The gastrointestinal tract is a unique immunological environment where the host must balance tolerance to commensal microbes with defense against pathogens. A critical mechanism for maintaining this balance is the peripheral conversion of naive T cells into regulatory T cells (pTregs), a process that depends on the TGF-{beta} cytokine, which is produced in a latent form and must be activated. While the activation of latent TGF-{beta} relies on the membrane-bound v{beta}8 integrin, the precise cellular subset(s) responsible for this essential process have yet to be clearly defined. Conventional dendritic cells (cDCs), which migrate from the intestinal lamina propria to the gut-draining mesenteric lymph nodes (MLN), have long been considered the primary antigen-presenting cells (APCs) responsible for v{beta}8-mediated TGF-{beta} activation and pTreg induction. However, recent studies have challenged this paradigm by highlighting a new family of rare ROR{gamma}t-expressing APCs, able to induce pTreg via v integrins, raising questions about the in vivo role of cDCs in the maintenance of mucosal immune homeostasis. Using a {beta}8 integrin gene reporter mouse model (Itgb8-IRES-tdTomato) combined with single-cell profiling, we comprehensively mapped Itgb8-expressing APCs in the MLN. We show that cDCs, in particular migratory type 1 (cDC1) and type 2 (cDC2), constitute the predominant Itgb8TdTomato+ cells, both in neonatal and adult mice. Through cDC subset-specific {beta}8 knockout models, we demonstrate that both cDC1 and cDC2 are required for optimal pTreg generation. Loss of {beta}8 integrin in either subset led to a partial reduction in pTreg, while combined deletion resulted in profound pTreg loss and spontaneous colitis. Importantly, these effects were independent of ROR{gamma}t APC populations, including ILC3s and Thetis cells. These findings resolve longstanding questions about the identity of key APCs driving pTreg induction in the MLNs. They demonstrate that cDC1 and cDC2 are non-redundant, essential mediators of pTreg induction and intestinal immune tolerance. Although different populations of ROR{gamma}t APCs may contribute in specific contexts, such as early development, infection, or in the prevention of allergic disease, cDCs remain one of the primary guardians of intestinal immune homeostasis in response to microbiota.

immunology↗

bioRxiv2024

Unveiling novel conserved HIV-1 open reading frames encoding T cell antigens using ribosome profiling.

The development of ribosomal profiling (Riboseq) revealed the immense coding capacity of human and viral genomes. Here, we used Riboseq to delineate the first translatome of HIV-1 in infected CD4+ T cells. In addition to canonical viral protein coding sequences (CDSs), we identify 98 alternative open reading frames (ARFs), corresponding to small Open Reading Frames (sORFs) that are distributed across the HIV genome including the UTR regions. Using a database of HIV genomes, we observed that most ARF amino-acid sequences are likely conserved among clade B and C of HIV-1, with 8 ARF-encoded amino-acid sequences being more conserved than the overlapping CDSs. Using T cell-based assays and mass spectrometry-based immunopeptidomics, we demonstrate that ARFs encode viral polypeptides. In the blood of HIV-infected individuals, ARF-derived peptides elicit potent poly-functional T cell responses mediated by both CD4+ and CD8+ T cells. Our discovery expands the list of conserved viral polypeptides that are targets for vaccination strategies and might reveal the existence of viral microproteins or pseudogenes.

immunology↗

bioRxiv2024

IL-1β Signaling Modulates T Follicular Helper and Regulatory Cells in Human Lymphoid Tissues

BackgroundDysregulation of the T follicular helper (Tfh) and T follicular regulatory (Tfr) homeostasis in the germinal center (GC) can result in antibody-mediated autoimmunity. While interleukin-1{beta} (IL-1{beta}) has been shown to be an important modulator of the GC response in animal models via the expression of IL-1 agonist (IL-1R1) and antagonist (IL-1R2) receptors on follicular T cells, such regulation has not yet been studied in humans. MethodsWe investigated Tfh and Tfr phenotypes in human secondary lymphoid organs -- namely tonsils, spleens, and mesenteric lymph nodes -- using flow cytometry, single-cell transcriptomics, and in vitro cell culture. We also benchmarked our findings with a cohort of patients with autoimmune and inflammatory diseases. ResultsWe found that Tfh and Tfr cells exhibit organ-specific phenotypes related to their activation status and IL-1 receptor expression. An excess of IL-1R1 over IL-1R2 was linked to the emergence of a unique activated Tfr subset that combines features of both Treg and GC-Tfh cells. Single-cell transcriptomics and in vitro studies showed that IL-1{beta} signaling through IL-1R1 promotes follicular T-cell activation. Inhibiting IL-1{beta} resulted in upregulation of IL-1R1 expression, showing a fine-tuned regulation. In autoimmune patients, high IL-1{beta} and circulating Tfr levels correlated with higher autoantibody levels, linking inflammation, IL-1{beta} signaling, and the Tfr/Tfh balance. ConclusionsOur study underscores the pivotal role of IL-1{beta} in follicular T-cell activation, contributing to pathological antibody production in humans. Targeting IL-1{beta} signaling in Tfh and Tfr cells could offer new treatment strategies for antibody-mediated autoimmune diseases.

immunology↗

bioRxiv2024

Expression of IL-1R2 by Tfr prevents their IL-1-dependent proliferation and the exacerbation of allergy

The antibody response is regulated by follicular T helper (Tfh) and regulatory (Tfr) cells that control the germinal center (GC) reaction. Recent research has shown that Tfh/Tfr have a unique pattern of IL-1 receptor expression. We investigated the mechanisms by which this IL-1 axis in GCs could regulate the allergic response. To study this, we generated CD4creIL-1R1lox mice, specifically lacking IL-1R1 expression in T cells and FoxP3creIL-1R2lox mice, specifically lacking IL-1R2 expression in Tfr cells. The conditional knockout mice were compared to their respective control mice in a model of ovalbumin (OVA) sensitization and anaphylaxis, and a phenotypic and functional characterization of humoral and cellular responses was performed. While CD4creIL-1R1lox mice showed little phenotypic changes, FoxP3creIL-1R2lox mice were highly susceptible to allergic anaphylaxis and generated an increase in IgE responses that promoted basophil degranulation. Additionally, FoxP3creIL-1R2lox mice displayed significantly reduced OVA-specific IgG responses, limiting their ability to control allergy via the inhibitory IgG receptor Fc{gamma}RIIb. Although FoxP3creIL-1R2lox mice showed an overall increase in splenic T and B cell numbers, they were unable to efficiently generate proliferating GC B cells. Upon ex vivo IL-1{beta} and/or OVA re-stimulation, we observed a striking IL-1R1-dependent activation and proliferation of Tfr cells in FoxP3creIL-1R2lox splenocytes, that was neither observed in Tregs nor in Tfh. At the same time, B cell proliferation upon re-stimulation was suppressed. These findings suggest that IL-1R2 expression on Tfr cells prevents allergy by limiting excessive Tfr activation and suppressing the IgG/IgE ratio.

immunology↗

bioRxiv2023

Interleukin-1 regulates follicular T cells during the germinal center reaction

Antibody production by plasma cells and generation of long-term memory B-cells are positively regulated by Tfh cells and negatively regulated by Tfr cells in germinal centers. However, the precise role of Tfr cells in controlling antibody production is still unclear. We have previously shown that Tfh and Tfr cells both express IL-1R1, while only Tfr cells express the IL-1R2 decoy and IL-1Ra antagonist receptors. To study the role of these receptors in the regulation of the B cell response by Tfh and/or Tfr cells, we generated mice with knockout of IL-1 receptors in Tfh and/or Tfr cells and measured antibody production and cell activation upon immunization. We showed that IL-1{beta} concentration is increased in the draining lymph node after immunization. Antigen-specific antibody levels and cell activation phenotypes indicated that IL-1{beta} can activate both Tfh and Tfr cells through IL-1R1 stimulation. Surprisingly, IL-1R2 and IL-1Ra expression on Tfr cells does not block IL-1 activation of Tfh cells, but rather prevents IL-1/IL-1R1-mediated early activation of Tfr cells. IL-1Rs similarly regulate antibody response against autoantigens and its related pathophysiology in an experimental lupus model. Altogether, these results show that IL-1R1 inhibitory receptors expressed by Tfr cells prevent their own activation and suppressive function, thus licensing IL-1-mediated activation of Tfh cells after immunization. One Sentence SummaryFunctional knockout of IL-1 agonist (R1) and antagonist (R2 and Ra) receptors reveals that IL-1-R2 and -Ra on Tfr cells prevent their own early activation to license the expansion and activation of Tfh cells after immunization.

immunology↗

bioRxiv2021

The Autophagy Receptor TAX1BP1 (T6BP) is a novel player in antigen presentation by MHC-II molecules.

CD4+ T lymphocytes play a major role in the establishment and maintenance of immunity. They are activated by antigenic peptides derived from extracellular or newly synthesized (endogenous) proteins presented on the surface of antigen presenting cells (APCs) by the MHC-II molecules. The pathways leading to endogenous MHC-II presentation remain poorly characterized. We demonstrate here that the autophagy receptor, T6BP, influences both autophagy-dependent and -independent endogenous presentation of HIV- and HCMV-derived peptides. By studying the immunopeptidome of MHC-II molecules, we show that T6BP affects both the quantity and quality of peptides presented. T6BP silencing induces the mislocalization of the MHC-II-loading compartments and a rapid degradation of the invariant chain (CD74) without altering the expression and internalization kinetics of MHC-II molecules. We determined the interactome of T6BP, identified calnexin as a T6BP partner and show that CANX cytosolic tail is required for this interaction. Remarkably, calnexin silencing replicates the functional consequences of T6BP silencing: decreased CD4+ T cell activation and exacerbated CD74 degradation. Altogether, we unravel T6BP as a key player of the MHC-II-restricted endogenous presentation pathway and we propose one potential mechanism of action.

immunology↗