Journal of Experimental Medicine最新文献

Excess TNF causes systemic inflammatory response syndrome and mortality. RIPK1 coordinates TNF signaling through kinase-dependent and -independent mechanisms. S161 autophosphorylation is a primary function of RIPK1 kinase activity in vitro, and here we show that it is sufficient to mediate RIPK1 kinase-dependent function in vivo. S161 phospho-mimic mutation (S161E) effectively overcomes chemical or genetic inhibition of RIPK1 kinase activity in TNF-treated cells and mice. Mechanistically, S161 autophosphorylation is necessary for further autophosphorylation in RIPK1, including at S166. Ripk1S161E/S161E mice are hypersensitive to TNF, enabling us to observe low-dose TNF-induced necroptosis in cecal intestinal epithelial cells (IECs) and endothelial cells (ECs) and uncover a reciprocal enhancement between IEC and EC necroptosis and a selective increase of IL-6 in the circulation by necroptosis. IL-6 promotes cecal edema and synergizes with IEC and EC necroptosis, causing cecal damage and mouse death. Our data elucidate a mechanism of RIPK1 kinase-dependent function in TNF signaling and its role in cecal pathology and mouse mortality.

MAIT cells are innate-like T cells known for their semi-invariant TCR that recognizes vitamin B metabolites presented by MR1. While the involvement of TCR and cytokines in development and activation of MAIT cells is well documented, the contribution of co-receptors, including SLAM family receptors, remains poorly understood. This study revealed that CD2 and its ligands, CD48 in mice and CD58 in humans, were crucial for MAIT cell maturation and antigen-driven activation, but not for their responses to cytokines. Cis interactions of CD2 with its ligands on the same cell were essential for activation, with trans interactions contributing in some contexts. A natural subset of human MAIT cells lacking CD2 displayed reduced activation responses to antigen. Human CD48 recognized 2B4 rather than CD2, dampening TCR signal strength and activation of human MAIT cells. Thus, the interplay between CD2 and its ligands is pivotal for MAIT cell development and activation, highlighting potential approaches for treating human diseases implicating MAIT cells.

CD4+ T cell-mediated control of tuberculosis (TB) requires recognition of macrophages infected with Mycobacterium tuberculosis (Mtb). Yet, not all Mtb-specific T cells recognize infected macrophages. Using infected monocyte-derived macrophages and autologous memory CD4+ T cells from individuals with stable latent Mtb infection (LTBI), we quantify the frequency of activated T cells. T cell antigen receptor (TCR) sequencing revealed >70% of unique and >90% of total Mtb-specific TCR clonotypes in LTBI are linked to recognition of infected macrophages, while a subset required exogenous antigen exposure, suggesting incomplete recognition. Clonotypes specific for multiple Mtb antigens, and other pathogens, were identified. Remarkably, antigen screening revealed all TCRs to be specific for type VII secretion system (T7SS) substrates. Mtb-specific clonotypes expressed signature effector functions dominated by IFNγ, TNF, IL-2, and GM-CSF or chemokine production and signaling. We propose that TB vaccines, which elicit T cells specific for T7SS substrates, recognize infected macrophages, and express canonical effector functions, will offer protection against TB.

In multiple sclerosis (MS), the leptomeninges (LM) are populated with immune cell aggregates that correlate with disease progression. The impact of LM inflammation on the adjacent dura is largely unknown. Using a mouse model of MS that induces brain LM inflammation and age-dependent disease progression, we found that encephalitogenic T cells and B220high B cells accumulate substantially in the brain LM and parenchyma of both young and aged mice, while the adjacent dura remains relatively inert. We also observed a population of anti-CD20-resistant B220low B cells in the dura and bone marrow that virtually disappear at disease onset and accumulate in the brain of young mice concomitant with disease remission. In contrast, aged mice show a paucity of brain-resident B220low B cells at the expense of class-switched B220high B cells accompanied by severe, chronic disease. In summary, dynamic changes in the brain, LM, and dural B cells are associated with age-dependent disease severity in an animal model of progressive MS.

Esther Obeng is an attending physician and associate professor at Emory University School of Medicine, where she leads a research group focused on myelodysplastic syndromes (MDS). Esther's team is investigating how normal hematopoietic stem cells develop into cancerous cells, as well as developing targeted therapies for MDS patients. We recently spoke to Esther about her move from St. Jude Children's Research Hospital to Emory, how her patients inform her research, as well as the joys and struggles of having running as a hobby.

RIPK1 regulates cell death and inflammation and has been implicated in the pathogenesis of inflammatory diseases. RIPK1 autophosphorylation promotes cell death induction; however, the underlying mechanisms and the role of specific autophosphorylation sites remain elusive. Using knock-in mouse models, here we show that S161 autophosphorylation has a critical physiological function in RIPK1-mediated cell death and inflammation. S161N substitution partially suppressed RIPK1-mediated catalytic activity and cell death induction but was sufficient to prevent skin inflammation induced by keratinocyte necroptosis or apoptosis in relevant mouse models. Combined S161N and S166A mutations synergized to prevent RIPK1-mediated cell death more efficiently than the single site mutations, revealing functional redundancy. Moreover, phosphomimetic S161E mutation could overcome the necroptosis-inhibitory effect of S166A mutation, revealing that S161 phosphorylation is sufficient for necroptosis induction. Collectively, a functional interplay of S161 and S166 phosphorylation events regulates RIPK1-dependent cell death and inflammation.

The placenta combats mother-to-fetus transmission of viruses through the antiviral activities of fetal-derived trophoblasts. Placental trophoblasts employ specialized antiviral strategies to protect against infection while preventing maternal immune rejection of the fetus. However, the full extent of how trophoblasts respond to viral infections is not well understood. To address this, we defined the transcriptional landscape of human trophoblast organoids infected with seven diverse teratogenic viruses. We found that herpesviruses, including HSV-1, HSV-2, and HCMV, did not trigger an IFN response. Instead, they activated the expression of DUX4 and its downstream target genes: DUX4-stimulated genes (DSGs). This program was enriched in trophoblasts and associated with cells containing low HSV-1 gene expression following infection. Screening highly expressed DSGs revealed that many of them exhibited anti-herpesvirus activity, indicating they comprise an alternative antiviral pathway similar to the IFN-stimulated gene response. These findings identify DUX4 as a master regulator of an antiviral program in trophoblasts, specifically targeting a prominent family of teratogenic viruses.

Development of invariant natural killer T (iNKT) cells in the thymus requires cell-cell interaction through invariant TCR (iTCR) and CD1d, which induces expression of the transcription factor, promyelocytic leukemia zinc finger (PLZF). However, the signaling pathway linking iTCR and PLZF remains unclear. Here, we report that a serine/threonine kinase, protein kinase D (PKD), plays a pivotal role in iNKT cell development. In T cell-specific PKD-deficient (Prkd2/3∆CD4) mice, PLZF induction and iNKT cell generation were severely impaired, which were rescued by introduction of a PLZF transgene. We identified the transcription factor Ikaros as a substrate of PKD upon iTCR stimulation. Knock-in mice carrying a phosphorylation-defective mutant Ikaros (Ikzf1S267/275A) exhibited an impairment of iNKT cell development, whereas conventional T cells were normal. In iNKT cells, Ikaros binds to the upstream region of the PLZF gene to induce its transcription. Mutant mice lacking the Ikaros-binding site (Zbtb16∆IBS) generated fewer iNKT cells than WT mice. These results suggest that PKD links iTCRs to PLZF induction through Ikaros, thereby mediating iNKT cell development.

In this issue of JEM, Zhou et al. (https://doi.org/10.1084/jem.20250153) report that hematopoietic progenitors heterozygous for the JAK2V617F mutation preferentially activate STAT1, promoting platelet production and thrombocythemia, whereas homozygous progenitors activate STAT5, leading to erythrocytosis and polycythemia.

The ocular surface is a mucosal barrier tissue colonized by commensal microbes, which tune local immunity by eliciting IL-17 from conjunctival γδ T cells to prevent pathogenic infection. The commensal Corynebacterium mastitidis (C. mast) elicits protective IL-17 responses from conjunctival Vγ4 T cells through a combination of γδ TCR ligation and IL-1 signaling. Here, we identify Vγ6 T cells as a major C. mast-responsive subset in the conjunctiva and uncover its unique activation requirements. We demonstrate that Vγ6 cells require both extrinsic (via dendritic cells) and intrinsic TLR2 stimulation for optimal IL-17A response. Mechanistically, intrinsic TLR2 signaling was associated with epigenetic changes and enhanced expression of genes involved in fatty acid oxidation to support Il17a transcription. We identify a key transcription factor, IκBζ, which is upregulated by TLR2 stimulation and is essential for this program. Our study highlights the importance of intrinsic TLR2 signaling in driving metabolic reprogramming and production of IL-17A in microbiome-specific mucosal γδ T cells.