This is a mechanism module, not a specific disease. Disorder entries reference individual nodes via conforms_to (e.g. "cdc1_tolerogenic_maturation#Tolerogenic Maturation to CCR7+ Late-Mature cDC1s"). The key conformance target is that central_effector node — the disorder-agnostic, rate-limiting step every conformer funnels through.
SPECIES SCOPE — READ BEFORE CONFORMING. The EPOR-cDC1 mechanism curated here is established entirely in mouse (conditional Epor, Itgb8 and MHCII deletion under Xcr1-Cre; Epor-tdTomato and Zbtb46-GFP reporters; allogeneic bone-marrow and heterotopic heart transplantation; B16F10-OVA and MC38-OVA tumours). The clinical total lymphoid irradiation / anti-thymocyte globulin regimen that motivates the model is used in human kidney transplantation, but no step of the EPOR-dependent chain has been demonstrated in human cDC1s. Do not curate a human disorder node as conforming to this module on the strength of this evidence alone; see the HUMAN_MODEL_MISMATCH discussion. A conforming node in a human disease entry needs its own human-derived evidence, or should be curated as a mechanistic_hypothesis with EMERGING status rather than as an asserted mechanism.
Positive conformance to the central effector requires more than "a dendritic cell matured". It requires (i) cDC1 lineage specifically — not cDC2, plasmacytoid DC, or monocyte-derived DC, since EPOR responsiveness is cDC1-restricted in this system; (ii) uptake of cell-associated (dying-cell) antigen rather than soluble or microbial antigen; and (iii) a tolerogenic outcome — antigen-specific FOXP3+ Treg induction or demonstrated restraint of antigen-specific priming. CCR7 upregulation alone is not sufficient: CCR7+ maturation is the shared gateway to BOTH the tolerogenic and the immunogenic program, which is precisely the point of the EPOR switch, so a CCR7+ mregDC-like node without a tolerogenic readout does not conform.
Disorder-specific substitutions conforming entries make: the dying-cell source (irradiated apoptotic lymphocytes; apoptotic tumour cells; homeostatic apoptotic cells in skin, lung or brain); the cDC1 compartment (splenic XCR1+CD8-alpha+ versus peripheral-lymph-node migratory XCR1+CD103+, which preferentially expresses EPOR); and the tolerated antigen (donor alloantigen, tumour antigen, self antigen).
Relationship to neighbouring modules. This is NOT a duplicate of immune_checkpoint_blockade, which models the tumour-cell-intrinsic adaptive immune resistance arm (PD-L1 upregulation, T cell exhaustion); this module models the antigen-presenting-cell-intrinsic arm upstream of it, and a tumour entry may reasonably conform to both. It is likewise distinct from tumor_promoting_inflammation (myeloid inflammatory microenvironment, not cDC1 maturational state). The Aldh1a2 / retinoic-acid route to Treg induction is deliberately NOT curated as part of the chain: cDC1-restricted Aldh1a2 deletion did not impair chimerism or donor-specific Treg induction in this system, so integrin beta-8 rather than retinoic acid is the EPOR-controlled effector here.
Does the EPOR switch govern tolerogenic maturation of human cDC1s, or is it a mouse-specific feature of the systems in which it was discovered?
HUMAN MODEL MISMATCH
OPEN
human_model_mismatch_cdc1_epor_switch
Attached to:
EPO-EPOR Signalling in cDC1s
Tolerogenic Maturation to CCR7+ Late-Mature cDC1s
Every causal step in this module rests on mouse genetics — conditional Epor, Itgb8 and H2-Ab1 deletion under Xcr1-Cre, Epor-tdTomato and Zbtb46-GFP reporters, allogeneic bone-marrow and heterotopic heart transplantation, and transplantable B16F10-OVA and MC38-OVA tumours. The translational pull is real: the total lymphoid irradiation plus anti-thymocyte globulin regimen that frames the model is used in human kidney transplantation to achieve mixed chimerism and drug-free tolerance, and erythropoiesis-stimulating agents are widely used in humans, so a human counterpart of this mechanism would have immediate clinical consequences in both directions. But the pull is not evidence. Mouse and human cDC1s are identified by different surface programs (mouse XCR1+CD8-alpha+ or CD103+; human CD141/BDCA-3+), and EPOR expression on human cDC1s, its regulation by efferocytosis, and its control of ITGB8 have not been shown. This matters for curation because the mismatch is not a question of effect size but of whether the switch exists at all in humans; a human disease entry asserting conformance would be importing an unverified species assumption into an otherwise evidence-backed graph.
Proposed experiments:
EPOR expression and efferocytosis-dependence on human cDC1s
EPO-dependence of human cDC1 Treg induction and ITGB8 induction
Does therapeutic erythropoiesis-stimulating agent exposure in patients alter cDC1 tolerogenic programming, and could that contribute to outcomes in transplantation or oncology?
KNOWLEDGE GAP
OPEN
knowledge_gap_esa_exposure_and_cdc1_tolerance
Attached to:
EPO-EPOR Signalling in cDC1s
Antigen-Specific FOXP3+ Treg Induction and Restrained T Cell Priming
If the switch operates in humans, then erythropoiesis-stimulating agents — given routinely for anaemia of chronic kidney disease, in transplant recipients, and in oncology — would be acting on it as an unintended pharmacology, in the tolerogenic direction. That predicts opposite-signed effects in the two settings where these agents are most used: potentially favourable for graft tolerance, potentially unfavourable for anti-tumour immunity. This is stated here as an open question and explicitly NOT as a curated mechanism. The source study neither administered these agents to patients nor examined human tumour outcomes, and the existing clinical safety literature on erythropoiesis-stimulating agents and tumour progression was generated without reference to cDC1 biology and has its own confounding; connecting the two would require evidence that does not yet exist. Curators should not cite this module as support for a mechanistic claim about erythropoiesis-stimulating agent safety.
Proposed experiments:
cDC1 phenotype in patients on erythropoiesis-stimulating agents
Efferocytic Uptake of Cell-Associated Antigen by cDC1s
trigger
cDC1s take up dying cells and their associated antigens by efferocytosis. This is the lineage-defining function that puts cDC1s in a position to determine the fate of responses to cell-associated (as opposed to soluble or microbial) antigen. The dying-cell source is what conforming disorder entries substitute: apoptotic lymphocytes generated by lymphodepleting conditioning, apoptotic tumour cells in the tumour microenvironment, or apoptotic cells cleared at homeostasis in peripheral tissue. Efferocytic load, together with circulating EPO, sets both the fraction of cDC1s expressing EPOR and the intensity of that expression, so this node is the input that scales the whole chain rather than a mere prerequisite.
Downstream
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EPO-EPOR Signalling in cDC1s
Efferocytosis of dying cells upregulates EPOR on cDC1s, licensing them to respond to erythropoietin.
Show evidence (1 reference)
"RNA–seq and Gene Ontology (GO) analysis of XCR1+CD8α+ cDC1s after TLI/ATS revealed upregulation of genes involved in phagocytosis, apoptotic cell clearance, erythropoiesis, and myeloid cell migration"
Transcriptional profiling of splenic cDC1s after lymphodepleting conditioning shows coordinated upregulation of the efferocytosis and erythropoiesis programs, establishing dying-cell uptake as the input state of this chain.
EPO-EPOR Signalling in cDC1s
amplifier
Erythropoietin receptor expressed on cDC1s binds erythropoietin and activates the AKT-mTOR, ERK and STAT5 cascades. This is the switch node of the module: EPOR is not a marker of a distinct cDC1 subset but a transcriptional program that cDC1s across the maturational continuum can enter, and its signalling output determines which maturational program follows. Responsiveness is cDC1-restricted — cDC2s in the same tissue show minimal pathway activation — which is why conformance requires cDC1 lineage specifically. Both ligand availability (circulating EPO, which rises with lymphodepleting conditioning and with tumour burden) and receptor abundance (driven by efferocytic load) are rate-setting, so the node is manipulable from either side; this is the basis of the treatment pattern below.
Downstream
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Tolerogenic Maturation to CCR7+ Late-Mature cDC1s
EPOR signalling drives efferocytosis-induced tolerogenic maturation towards the late-mature CCR7+ state.
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Immunogenic cDC1 Maturation and Enhanced T Cell Priming
The reciprocal branch: when EPOR signalling is absent, the same efferocytic cDC1s mature along an immunogenic rather than a tolerogenic route.
Show evidence (2 references)
"Here we show that the erythropoietin receptor (EPOR) acts as a critical switch that determines the tolerogenic function of cDC1s and the threshold of antigen-specific T cell responses."
States the central claim of the module: EPOR is the switch setting cDC1 tolerogenic function and the threshold of antigen-specific T cell responses.
"increased phosphorylation of Akt, Erk, Stat5, S6, and 4E-BP1 (Extended Data Fig. 3d), with minimal activation in cDC2s"
Identifies the downstream signalling cascades engaged by EPOR in cDC1s and establishes the cDC1-restricted responsiveness that gates conformance.
Tolerogenic Maturation to CCR7+ Late-Mature cDC1s
central effector
Under EPOR signalling, efferocytic cDC1s progress along the maturational continuum to a late-mature CCR7+ state carrying a regulatory rather than a stimulatory program: increased integrin beta-8 (Itgb8), TGF-beta1, CCL22 and PD-L1 (Cd274), increased tolerance-associated genes, and reduced cross-presentation capacity. This is the key conformance target — the disorder-agnostic, rate-limiting step that every conforming disease funnels through, whatever the dying-cell source or anatomical compartment. Loss of EPOR both reduces the proportion of cells reaching this state and strips the regulatory program from the cells that do, so the node is defined by the program and not by CCR7 positivity alone. CCR7 upregulation is the shared gateway to the immunogenic route as well; a CCR7+ mregDC-like node without a tolerogenic readout does not conform.
Downstream
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Integrin alpha-V beta-8-Dependent Latent TGF-beta Activation
The late-mature CCR7+ state carries high integrin beta-8, the effector through which it acts on responding T cells.
Show evidence (3 references)
"of splenic cDC1s towards late-stage CCR7+ cDC1s characterized by increased expression of the integrin β8 gene"
States the maturational endpoint of EPOR signalling and its defining molecular feature, integrin beta-8 upregulation, which is the effector carried by the next node.
"towards late mature stage CCR7+ cDC1s and demonstrate that integrin β8, but not Aldh1a2, is a critical tolerogenic downstream mediator under EpoR control in TLI/ATS-induced tolerance"
Establishes integrin beta-8 rather than Aldh1a2/retinoic acid as the EPOR-controlled tolerogenic effector, which is why the retinoic-acid route is deliberately excluded from this module's chain.
"Migratory cDC1s in peripheral lymph nodes preferentially express EPOR, and their FOXP3+ Treg cell-inducing capacity is enhanced by erythropoietin."
Extends the node beyond the splenic compartment: migratory cDC1s in peripheral lymph nodes carry the same EPOR-dependent tolerogenic capacity, supporting the compartment substitution conforming entries make.
Integrin alpha-V beta-8-Dependent Latent TGF-beta Activation
effector
Integrin alpha-V beta-8 on late-mature CCR7+ cDC1s binds the latency-associated peptide of latent TGF-beta and converts it to active TGF-beta at the cDC1-T cell interface. This makes TGF-beta availability local and contact-dependent rather than a diffuse cytokine signal, which is how an antigen-presenting cell can impose a regulatory fate specifically on the T cells it is engaging. cDC1-restricted deletion of Itgb8 reproduces the Treg-induction defect seen on loss of EPOR, placing integrin beta-8 causally downstream of the switch rather than merely correlated with it — though the resulting impairment of chimerism is less complete than with EPOR deletion, indicating integrin beta-8 carries much but not all of the EPOR effect.
Downstream
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Antigen-Specific FOXP3+ Treg Induction and Restrained T Cell Priming
Locally activated TGF-beta drives naive antigen-specific CD4+ T cells to a FOXP3+ regulatory fate and supports expansion of preexisting Tregs.
Show evidence (2 references)
"αvβ8 contributes to peripheral Treg differentiation due to its ability to activate latent TGFβ"
States the molecular function of integrin alpha-V beta-8 that this node models: activation of latent TGF-beta driving peripheral Treg differentiation.
"14 days after allo-BM infusion, Treg frequencies increased in control mice but markedly decreased in Itgb8ΔXcr1 mice"
cDC1-restricted Itgb8 deletion phenocopies the Treg-induction defect of EPOR deletion, placing integrin beta-8 causally downstream of the EPOR switch.
Antigen-Specific FOXP3+ Treg Induction and Restrained T Cell Priming
consequence
The terminal state of the tolerogenic arm: antigen-specific CD4+FOXP3+ regulatory T cells are induced from naive precursors and preexisting Tregs are expanded, while CD8+ cross-priming and CD4+ priming against the same cell-associated antigen are held below threshold. The tolerance is antigen-specific rather than global immunosuppression, and it operates even at homeostatic EPO levels. Whether this outcome is beneficial or harmful is entirely context-dependent and is the reason the module serves opposite clinical goals: in transplantation and autoimmunity it is durable donor-specific or self-antigen-specific tolerance; in cancer it is tumour-antigen-specific tolerance with intratumoural Treg accumulation and blunted anti-tumour CD8+ T cell immunity. Conforming entries name the antigen and state which of these two readings applies.
Show evidence (2 references)
"cDC1s upregulate EPOR expression, and conditional knockout of EPOR in cDC1s diminishes antigen-specific induction and expansion of FOXP3+ regulatory T (Treg) cells, resulting in allograft rejection"
Establishes the terminal readout of the tolerogenic arm and its clinical consequence: loss of cDC1 EPOR abolishes antigen-specific Treg induction and expansion, and tolerance fails.
"even at low homeostatic EPO levels, cDC1-EpoR limits both CD8+ T cell cross-priming and CD4+ T cell priming in response to cell-associated Ags"
Establishes the second half of the terminal state — restraint of antigen-specific priming — and that it operates at homeostatic EPO levels, not only under conditioning.
Immunogenic cDC1 Maturation and Enhanced T Cell Priming
adaptive escape
The reciprocal branch of the switch, and the reason EPOR is described as a switch rather than an amplifier. When EPOR signalling is absent, efferocytic cDC1s do not simply fail to become tolerogenic — they mature along an actively immunogenic route, upregulating MHC class II- and class I-mediated antigen presentation, cross-presentation and costimulation (CD40, CD80, CD86) while downregulating PD-L1. In tumours this branch increases generation of precursor exhausted tumour-antigen-specific CD8+ T cells in tumour-draining lymph nodes, supports their maintenance intratumourally, reduces intratumoural Tregs, restrains tumour growth and improves the efficacy of PD-1 blockade. This node is curated as the mechanistic rationale for the tolerance-breaking treatment pattern below; it is reached experimentally by cDC1-restricted EPOR deletion, so a disorder node should conform to it only where an equivalent loss-of-EPOR state is actually demonstrated, not merely where cDC1s appear immunogenic.
Show evidence (2 references)
"Reciprocally, loss of EPOR enables immunogenic maturation of peripheral lymph node migratory and splenic CCR7+ cDC1s by upregulating genes involved in MHC class II- and class I-mediated antigen presentation, cross-presentation and costimulation."
States the reciprocal branch directly: EPOR loss does not merely remove tolerogenic maturation but enables an immunogenic maturational program at both anatomical sites.
"EPOR deficiency in cDC1s reduces tumour growth by enhancing anti-tumour T cell immunity, particularly increasing the generation of precursor exhausted tumour antigen-specific CD8+ T cells"
Establishes the anti-tumour consequence of the immunogenic branch, which is the rationale for the tolerance-breaking treatment pattern.
Erythropoietin as a cDC1 Tolerogenic Agonist
Platform:
Protein replacement
The tolerance-inducing arm of the module's drug-target pattern. Exogenous erythropoietin acts on the EPOR switch node to amplify cDC1 tolerogenic maturation and increase antigen-specific FOXP3+ Treg induction, including by cDC1s that were EPOR-low at baseline. The effect is strictly cDC1-EPOR-dependent: it is abolished when EPOR is deleted from cDC1s, so it is a mechanism-specific action and not a general consequence of erythropoiesis. This is a preclinical (mouse) drug-target pattern demonstrating the node is pharmacologically addressable — it is NOT a treatment recommendation, and conforming disorders do not inherit it as one. Recombinant erythropoietin is an approved drug for anaemia, but its use as a tolerogenic agent in transplantation or autoimmunity is not established in humans and would carry the known thrombotic and tumour-progression safety concerns of erythropoiesis-stimulating agents.
Evidence: 1
cDC1 EPOR Blockade as a Tolerance-Breaking Strategy
Platform:
Other
The tolerance-breaking arm of the same drug-target pattern, and the conceptual inverse of the agonist above. Removing EPOR signalling from cDC1s shifts them to the immunogenic branch, restraining tumour growth, increasing tumour-antigen-specific precursor exhausted CD8+ T cells in tumour-draining lymph nodes, reducing intratumoural Tregs and improving the efficacy of PD-1 blockade. This is a genetic proof of concept in mouse — cDC1-restricted Epor deletion — not an agent. No cDC1-selective EPOR antagonist exists, and systemic EPOR blockade would not be equivalent: EPOR is the erythropoiesis receptor, and the therapeutic proposition depends on cDC1 selectivity that has not been demonstrated. Curate this as a target rationale, never as an available treatment.
Evidence: 1