Journal of Experimental Medicine最新文献

Hematopoietic stem/progenitor cells (HSPC) aging has long been associated with myeloid skewing, reduced clonal output, and impaired regenerative capacity, but quantitative immunophenotypic and functional analysis across the human lifespan has been lacking. Here, we provide a comprehensive phenotypic, transcriptional, and functional dissection of human hematopoiesis from youth to advanced age. Although primitive hematopoietic stem cell (HSC) numbers were stable during aging, overall cellularity declined, especially for erythroid and lymphoid lineages. HSPCs from older individuals exhibited repopulating frequencies comparable with those from younger donors in both primary and secondary xenografts; however, aged HSCs displayed impaired differentiation, chromatin and cell cycle dysregulation, and poor tolerance to activation-induced proliferative stress, resulting in DNA damage and senescence-like features after xenotransplantation. Importantly, imposing proliferative stress on young human HSPCs in vivo recapitulated key aging-associated phenotypic and functional declines. Together, our findings identify dysregulated activation responses as a defining feature of HSPC aging and establish proliferative stress-based xenotransplantation models as powerful platforms for investigating age-related hematopoietic dysfunctions.

Clonal hematopoiesis driven by Tet2 deficiency in myeloid cells (TetΔMye) is prevalent in elderly individuals; however, the role of Tet2ΔMye in liver fibrosis pathogenesis remains elusive. In this study, we demonstrated that Tet2-deficient monocyte-derived macrophages (MDMs) promoted cellular expansion and elevated C-C motif chemokine ligand 2/8 (Ccl2/8) secretion by stabilizing their mRNAs through 5hmC-mediated alterations in RNA-protein interactions. These chemokines engaged with the upregulated C-C motif chemokine receptor (Ccr2/3) on Tet2-/- monocytes, forming a positive feedback loop that amplified pro-inflammatory MDMs (pMDMs) accumulation in liver. Tet2-/- pMDMs activated hepatic stellate cells through IL-6, driving extracellular matrix deposition and fibrotic progression. Pharmacological inhibition of Ccl2/Ccl8 with Bindarit attenuated MDMs accumulation and liver fibrosis, whereas combined therapy with Bindarit and IL-6 neutralization synergistically suppressed liver fibrosis in Tet2ΔMye mice and aged chimeric models recapitulating Tet2ΔMye-related myeloid hematopoiesis. These findings present the mechanism that Tet2ΔMye aggravates liver fibrosis and highlight MDMs depletion plus IL-6 neutralization as a promising therapy for liver fibrosis in patients with Tet2ΔMye-related myeloid hematopoiesis.

The mechanism by which one non-self antigen augments T cell immune responses to another remains unclear. We found that these expanded immune responses could derive from chimeric non-self peptides. These peptides, which we termed complete T cell antigens (CTAs), must be expressed intracellularly as single-chain chimeras containing both MHC class I- and II-restricted epitopes. CTAs, even unrelated to tumor antigens, when administered as live cell adjuvants or in cDNA-transfected muscle, increased T cell reactivity against tumor neoantigens. Mechanistically, CTA treatment altered dendritic cell phenotype in a CD4+ T cell-dependent manner, suppressing CD8+ T cell exhaustion and generating self-renewing CD8+ T cells in tumors. Cancers predicted to have long non-self peptides resulting from frameshift mutations, which frequently contain CTAs, were associated with a better prognosis or benefit from PD-1 blockade therapy in mouse models and cancer patients. These findings indicate that a subset of cancer cells expressing CTAs is sufficient to evoke overall antitumor immunity by broadening T cell responses to other neoantigens.

Inorganic phosphate (Pi) is an essential nutrient for all organisms. It has critical functions in lipid and nucleic acid synthesis, protein signaling and bone growth. Loss-of-function mutations in Pi transporters lead to embryonic and neonatal lethality. Here, we show that the only known Pi exporter, XPR1, is critical for the development of fetal macrophages in the liver and the spleen. Single-cell RNA-seq and flow cytometry analyses in conditional mice lacking Xpr1 in hematopoietic and/or CD206+ cells revealed loss of the Kupffer cell transcriptional program and a shift in the development of fetal liver monocytes towards an interferon-activated monocyte/macrophage state. Functionally, Xpr1 deficiency in embryos led to a failure to clear nuclei expelled from erythroblasts. In adulthood, splenic red pulp and bone marrow macrophages were also reduced upon loss of intrinsic Xpr1. Collectively, these findings reveal that XPR1 is required for the development, identity, and function of macrophages involved in erythropoiesis.

Amino acids are essential for the activation and function of CD4 T helper (Th) cells, which differentiate into Th1, Th2, Th17, and Treg subsets to coordinate immune responses. While specific amino acid transporters have been identified for Th1, Th17, and Tregs, a transporter regulating Th2 cells remains unknown. This study identifies SLC7A8 as a Th2-specific amino acid transporter in the Th compartment. We found that Slc7a8 expression is upregulated in Th2 cells compared with other T helper subsets, and Slc7a8 deficiency impairs Th2 cell proliferation and cytokine production. Furthermore, SLC7A8 was found to be crucial for an effective type 2 immune response to helminth infection and allergen-induced lung inflammation. Mechanistically, Slc7a8 deficiency disrupted Th2 cell metabolism, leading to reduced mTOR activation and, consequently, diminished mitochondrial function along with an impaired c-Myc pathway; these defects cumulatively induced cellular stress that curtailed cell growth and survival. Collectively, these findings highlight a previously unknown role for SLC7A8 in Th2 cells, with potential implications for understanding and treating type 2 immune-related diseases.

MHC class I-related protein (MR1) presents vitamin B-based antigens (Ags) to mucosal-associated invariant T (MAIT) cells. While microbial riboflavin (RF) precursors are well-documented MR1 ligands, it is unclear whether host-generated RF catabolites influence MR1 immunity. Here, we report that RF catabolites, including 10-formylmethylflavin (FMF), lumichrome, lumiflavin, and alloxazine, bind to MR1 with moderate affinity, while RF itself binds weakly. In contrast to the MR1-upregulating microbial RF precursors, RF catabolites reduced the surface level of MR1 by inducing its retention in the endoplasmic reticulum and inhibiting exit. These RF catabolites weakly competed with vitamin B-based Ags for MR1 binding, thereby selectively inhibiting MAIT activation. The crystal structures of MR1 with RF, FMF, lumiflavin, and lumichrome show binding in the A'-pocket of MR1. Here, lumichrome formed a "flavin bond" covalent interaction with MR1-Lys43 differing from the typical Schiff base. Collectively, we identified three-ringed isoalloxazines that bind MR1 and reduce surface levels, suggesting a potential role in dampening MAIT cell immunity.

Variants of uncertain significance (VUS) are a major obstacle in genetic diagnosis, particularly when involving gain-of-function (GoF) mutations that are poorly predicted in silico. MEFV, which encodes the inflammasome sensor pyrin, is mutated in two autoinflammatory diseases, familial Mediterranean fever (FMF) and pyrin-associated autoinflammation with neutrophilic dermatosis (PAAND). Here, we developed SpeckSeq, a method that combines DNA bar-coding, ASC speck-based single-cell sorting and next-generation sequencing to systematically identify hypermorphic MEFV variants in response to different stimuli. SpeckSeq identified 49 GoF mutations separated into two distinct groups containing either PAAND variants or FMF variants. SpeckSeq was validated using patients' cells and supported a reclassification of MEFV variant pathogenicity, leading to novel diagnoses. As a large-scale mutagenesis approach, using human genetics as a guide, SpeckSeq revealed structural and functional pyrin features, including a putative ligand-accommodating cavity in the B30.2 domain. Altogether, SpeckSeq classifies VUS to refine molecular diagnostics and improve our knowledge on the pyrin inflammasome.

Insights into HIV-1 pathogenesis have come from studies of viral dynamics. However, there is little information on viral dynamics in lentiviral infections in which viral replication is naturally controlled in a subset of infected individuals. We evaluated the decay of simian immunodeficiency virus (SIV) RNA and cell-associated SIV genomes in a nonhuman primate (NHP) model in which replication of an engineered SIV variant is naturally controlled by cellular immune responses in most infected animals. This variant lacks a trafficking motif in the gp41 cytoplasmic tail. A trajectory of control was evident by 21 days after infection. In animals with natural control, we observed similar biphasic decay of intact proviruses in blood and lymph nodes, at rates close to those in animals that failed to control the virus and were put on antiretroviral therapy (ART). Both natural control and ART effectively blocked viral evolution, but not persistence. Thus, in this NHP model, natural control can be nearly as effective as ART in controlling viral replication.

T cell engagers (TCEs) are antibody-based constructs designed to transiently reprogram cytotoxic T lymphocytes for target cell elimination by simultaneously binding the T cell receptor and a specific surface antigen on the target cell. Over the past 12 years, 10 TCEs were approved by the US Food and Drug Administration, and an additional two by the European Medicines Agency. Nine TCEs treat hematologic malignancies, and three target solid tumors. Over 150 TCEs are being investigated in clinical trials, recently also in autoimmune diseases. Here, we discuss the learnings from the 12 approved TCEs. A surprising variety of molecular designs and biochemical characteristics appear suitable for approval. On the clinical side, we review targets, indications, dosing, schedules, side effects, mitigation strategies for adverse events, and efficacy. High flexibility in design and choice of target, scalability, high response rates as a monotherapy in hematologic malignancies, and emerging efficacy against solid tumors and in autoimmune diseases make TCEs an attractive therapeutic modality.