Journal of Leukocyte Biology

BackgroundTrained immunity is a durable functional reprogramming of innate immune cells characterized by enhanced responsiveness upon secondary challenge. While metabolic rewiring and epigenetic remodeling are well-established features of this process, the contribution of ubiquitin-mediated post-translational regulation remains poorly defined. MethodsWe performed an integrative analysis of publicly available human transcriptomic datasets derived from monocytes, macrophages, and PBMCs exposed to established training stimuli ({beta}-glucan, Bacillus Calmette-Guerin [BCG], and hemin-{beta}-glucan) followed by secondary stimulation. A curated panel of deubiquitinating enzymes (DUBs) and E3 ubiquitin ligases with established immune functions was analyzed for differential expression. Gene Ontology (GO) and KEGG pathway enrichment analyses were conducted to evaluate higher-order convergence across independent datasets. ResultsAcross multiple trained immunity models, we identified reproducible transcriptional remodeling of ubiquitin-modifying enzymes. USP25, OTUB1, and TRIM25 were consistently upregulated following restimulation, whereas several chromatin- and cytokine-regulatory DUBs--including USP3, USP4, USP7, USP16, MYSM1, and USP38--were downregulated. Normalization to RPMI-restimulated controls reduced many activation-associated signals; however, USP25 remained persistently elevated, suggesting a stable training-associated signature. Pathway enrichment analysis independently demonstrated significant engagement of ubiquitin-related functional categories across datasets, supporting coordinated reorganization of ubiquitin regulatory networks. ConclusionThese findings identify selective transcriptional remodeling of the ubiquitin- proteasome system as a recurring feature of trained immunity. Integrating ubiquitin signaling into the established metabolic-epigenetic framework expands the conceptual model of innate immune memory and suggests that ubiquitin-modifying enzymes function as modulatory rheostats shaping immune amplitude and stability. Future functional and proteomic studies are required to determine whether these transcriptional signatures directly mediate trained immunity phenotypes.

We show that clonal hematopoiesis is associated with an increased incidence of autoimmune hemolytic anemia. The hazard ratios of autoimmune hemolytic anemia and immune thrombocytopenia associated with clonal hematopoiesis were similar.

Alveolar macrophages (AMs) are tissue-resident and the primary immune cells in the airspace. Following perturbations in the lungs, these AMs that are derived from the fetal liver, become depleted and are transiently replaced by myeloid cells that use lung-specific cues to differentiate into myeloid-derived AMs. While these myeloid-derived AMs are critically important in a range of pulmonary diseases, including post-influenza bacterial pneumonia, it remains challenging to fully understand their function due to a lack of ex vivo models that recapitulate key differences observed in vivo between AMs and myeloid-derived AMs. Here, we overcome this limitation by expanding our recently developed model of fetal liver-derived alveolar macrophages (FLAMs) to differentiate myeloid progenitors in the presence of GM-CSF and TGF{beta}, key cytokines that drive tissue resident AM functions. These myeloid-derived alveolar-like macrophages (MAMs) express AM surface markers and look similar morphologically to FLAMs, however, they remain more inflammatory than FLAMs. Mechanistic studies found that differential CpG methylation at inflammatory loci, basal transcriptional expression, and metabolic flux all contribute to the hyperinflammatory state of MAMs. Importantly, we find that while FLAMs are highly dependent of lipid metabolism, MAMs are more glycolytic and this hardwired metabolism is not easily overcome to mute their inflammatory state. Finally, we found that MAMs and FLAMs both function within the lung environment following transfer into mice lacking AMs. While both MAMs and FLAMs stably seed the lungs and reverse pulmonary proteinosis, MAMs remain highly inflammatory in the lungs following an LPS model of acute lung injury. Taken together our results find that MAMs are a reproducible model of myeloid-derived AMs and lays the groundwork to better understand how these important immune cells contribute to pulmonary homeostasis and responses to lung perturbations. These future studies will help to identify new targets that can be modulated to prevent severe pulmonary disease outcomes.

Objective: To characterize genome-wide DNA methylation patterns associated with sepsis using the Infinium Methylation EPIC v2.0 platform and to evaluate the feasibility of pooled methylation profiling in a pilot critical care cohort. Design: Single-center pilot epigenome-wide association study using pooled whole-blood genomic DNA and pool-level bioinformatic analysis. Setting: Academic medical center. Patients: Fifty critically ill adults enrolled within 48 hours of illness onset and 20 healthy controls. Interventions: None. Measurements and Main Results: Critically ill patients required mechanical ventilation and/or vasopressor support. Sepsis was defined according to Sepsis-3 criteria. Seventy individual samples were organized into 14 intended pools of 5 individuals each: 7 sepsis pools, 3 critically ill non-septic pools, and 4 healthy-control pools. One critically ill non-septic pool was excluded because of poor DNA quality, yielding 13 analyzable pools. For the primary pooled comparison, 7 sepsis pools were compared with 6 non-sepsis comparator pools comprising 2 critically ill non-septic and 4 healthy-control pools. After quality control and preprocessing with SeSAMe, 876,094 CpG sites were retained. The initial pool-level screen identified 170,897 candidate differentially methylated regions. Application of stringent secondary filters (false discovery rate <= 1%, absolute delta-beta >= 7.5%, and >= 5 CpGs per region) yielded a high-confidence subset with marked directional skewing, including 155 hypomethylated and 32 hypermethylated regions in sepsis. Differentially methylated region-associated genes were enriched in myeloid leukocyte activation, myeloid leukocyte-mediated immunity, defense response to bacterium, neutrophil granule biology, and hematopoietic cell lineage pathways. Additional signals involved microRNA-associated targets, ribosome biogenesis, RNA processing, long noncoding RNAs, and previously uncharacterized loci. Conclusions: In this pilot pooled EPIC v2.0 study, sepsis was associated with a biologically coherent, predominantly hypomethylated methylation signature enriched in myeloid and host-defense pathways. These findings support the feasibility of pooled methylation profiling for discovery-oriented sepsis biobank studies but should be interpreted as hypothesis-generating given the pool-level design, limited effective sample size, heterogeneous comparator group, and lack of direct validation against individual-level methylation profiles.

Haematopoiesis and differentiation of immune cells from haematopoietic stem and progenitor cells (HSPCs) are essential to core aspects of health and disease. A key player in haematopoiesis and HSPC differentiation is the cytoskeleton, which governs cell division and lineage bias. Despite insights using mouse models, regulation of haematopoiesis by the septin cytoskeleton is mostly unknown. Septins are unconventional filament forming proteins best known for roles in cell division and host defence. To investigate septin-mediated host defence in vivo, we generated septin-deficient zebrafish models for infection with Mycobacterium marinum. Unexpectedly, septin-deficient larvae were protected from mycobacterial infection due to significantly increased macrophage numbers, reduced cell death, and enhanced inflammatory responses. Underlying this, we found that septin-deficient larvae produce significantly more HSPCs and show myeloid lineage bias, establishing a requirement for septins in haematopoiesis. In agreement with classical HSPC hierarchy, increased myeloid production in septin-deficient larvae is at the expense of erythroid lineage production. Our findings that septins play a role in haematopoiesis is consistent with hallmarks of haematological disorders in which septin dysfunction has been implicated, including acute myeloid leukaemia, myelodysplastic syndrome, and platelet disorder Bernard-Soulier syndrome. These results highlight zebrafish as a new model to investigate septin-mediated haematopoiesis and application of septin-based medicines to treat blood disorders.

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease characterised by sustained type I interferon signalling and widespread immune dysregulation. Low-density neutrophils (LDNs) are expanded in SLE and display pro-inflammatory and tissue-damaging properties. However, their metabolic phenotype remains poorly defined. Here, we performed a comprehensive metabolic characterisation of circulating LDNs and normal-density neutrophils (NDNs) from patients with SLE and matched healthy individuals (HC). Neutrophil subsets were isolated from peripheral blood of SLE patients and HC donors using a two-step protocol of negative selection and Percoll density centrifugation. Immunophenotyping phenotype was carried out by flow cytometry to assess phenotypic expression of common neutrophil markers CD15, CD16, CD10, CD66b, CD62L, MPO, and IL-1{beta}. Bioenergetic profiling of LDNs and NDNs was performed in situ using the Seahorse MitoStress test to measure oxygen consumption rate (OCR) and extracellular acidification rate (ECAR). Metabolic flexibility and phenotypic alterations were assessed in LDNs and NDNs following inhibiting mitochondrial metabolism with oligomycin and glycolysis with 2DG. We found that SLE LDNs exhibit an immature phenotype compared with autologous and healthy NDNs, as determined transcriptionally by C/EBP{varepsilon} and by surface protein expression levels of CD10. Both LDNs and NDNs from SLEDAI[&ge;]4 patients demonstrated significantly elevated ECAR relative to HC neutrophils. Further, SLE LDNs displayed enhanced metabolic flexibility, with the capacity to switch towards a glycolytic phenotype under metabolic stress conditions. Inhibition of glycolysis altered the inflammatory and maturation-associated phenotype of both SLE neutrophil subsets, indicating a direct link between cellular metabolism and pathogenic neutrophil function. Collectively, these findings identify fundamental metabolic alterations in SLE neutrophil subsets and support neutrophil immunometabolism as a potential therapeutic target in SLE.

Patients with a dominant mutation in the Rho GTPase RAC2, RAC2E62K, which hyperactivates the protein, suffer from a combined immunodeficiency characterized by recurrent bacterial and fungal infections and severe T cell lymphopenia. Patient neutrophils have elevated F-actin and superoxide production yet fail to control growth of S. aureus, and the mechanism underlying this killing defect is unknown. Here we report that hyperactive Rac2 primes neutrophils for primary granule degranulation, potentially depleting myeloperoxidase (MPO) needed for intraphagosomal microbial killing. Using a Rac2+/E62K mouse model, we show that mature bone marrow neutrophils have decreased side scatter, elevated surface CD63, and reduced intracellular MPO. Interestingly, bone marrow architecture and neutrophil development in the mice are normal. Rac2+/E62K neutrophils are hyperactivated, with increased CD11b expression, cell spreading, and bioparticle phagocytosis. In the spleen, Rac2+/E62K mice display extramedullary granulopoiesis and an accumulation of degranulating neutrophils. Splenic T cells, but not B cells, show elevated surface phosphatidylserine, an "eat me" signal that sensitizes them to phagocytic clearance and provides a candidate mechanism for the selective T cell lymphopenia. Together these findings suggest that hyperactive Rac2 compromises antimicrobial neutrophil function and drives selective T cell clearance in the spleen.

Neutrophils recruited to the airways are important for innate lung defense and can release neutrophil extracellular traps (NETs) to capture and eliminate microbes. While NETs are not abundant in healthy airways, uncontrolled NETosis is a known pathological feature and contributor to both chronic and acute respiratory diseases. Prior studies have shown that mucin glycoproteins secreted in the oral cavity and cervicovaginal tract can modulate NETosis, but it remains unknown whether mucins secreted in the respiratory tract influence NET formation. In these studies, we discovered that human airway mucus strongly inhibits NETosis in primary human neutrophils in a sialic acid dependent manner. In comparison, mucus produced by human airway epithelial cells genetically engineered to lack either MUC5B or MUC5AC secreted airway mucins showed a reduced ability to suppress NETosis. To assess how the lung microenvironment in obstructive lung diseases may influence mucus-dependent NET formation, we engineered a synthetic, mucin-laden hydrogel model with physical properties resembling that of mucus in a healthy lung and a disease-affected lung. When neutrophils were cultured on these gel substrates, we found that increasing gel stiffness led to a significantly greater extent of NETosis. Together these data demonstrate a new functional role of airway mucus in modulating neutrophil homeostasis in the respiratory tract and provide evidence that mucus dysfunction in disease can impair its ability to regulate NETosis.

Klebsiella pneumoniae is a leading cause of pneumonia and bacteremia and is especially dangerous in healthcare settings. Despite massive clinical significance, the mechanisms used by macrophages to kill K. pneumoniae are not well defined. Macrophages are critical for controlling K. pneumoniae as mice lacking monocyte-derived or alveolar macrophages have higher bacterial tissue burdens and mortality. Two prominent mechanisms used by macrophages to kill bacteria are the production of reactive oxygen species (ROS) via the NADPH oxidase NOX2 and reactive nitrogen species (RNS) via the inducible nitric oxide synthase iNOS. Previously, we found that K. pneumoniae uses similar genetic factors to survive during bacteremia and within macrophages. The ability of these factors to enhance intracellular fitness was significantly correlated with resistance against RNS, not ROS. Here, we aimed to define whether macrophage ROS and RNS contribute to intracellular K. pneumoniae clearance. Using wild-type, Cybb-/-, and Nos2-/- cells, we measured K. pneumoniae survival within macrophages lacking such defenses. NOX2 was dispensable for K. pneumoniae clearance, and ROS was undetectable in K. pneumoniae-infected macrophages. We confirmed that ROS was undetectable within alveolar-like macrophages, indicating a conserved ROS evasion phenotype across macrophage subsets. Instead, iNOS significantly contributed to macrophage clearance of K. pneumoniae and enhanced cytokine production. iNOS likely enhances K. pneumoniae clearance through coordination of immunity and RNS. Activation of pathways upstream of iNOS may be the most relevant to supporting effective macrophage control of K. pneumoniae. This study defines unexpected differential roles for ROS and RNS in macrophage clearance of K. pneumoniae.

Mounting evidence indicates that T cells can operate in an innate-like mode challenging the classical description of T cells as strictly adaptive immune effectors. T cells can engage innate pattern recognition receptors to mount rapid but antigen-nonspecific responses to infection or cellular stress. This study observed that CD8+ T cells, and to a lesser extent also CD4+ T cells, responded to viral proteins in the mouse lung quickly in an innate-like fashion. We employed intravital lung microscopy to visualize infiltration of CD8+ T cells into the lung following intratracheal instillation of the SARS-CoV-2 envelope (E)-protein. Here, we demonstrate acute recruitment of CD8+ from the pulmonary microcirculation into the lung as early as 4 and 24 hours after (E)-protein instillation. The acute infiltration of CD8+ T cells was not observed in Tlr2-/- mice. Immunohistochemistry analysis of mouse lungs revealed T cell accumulation in nodular inflammatory foci (NIF) of the lung at perivascular regions and around large airways. Stimulating spleen-derived CD8+ T cells from wild-type mice with (E)-protein ex vivo in combination with cytokines or TCR agonists significantly upregulated CD69 and activated secretion of interferon (IFN){gamma} which was not observed with CD8+ T cells isolated from Tlr2-/- mice. These findings indicate rapid bystander activation of CD8+ T cells by the SARS-CoV-2 envelope (E)-protein that depends on (E)-protein sensing by TLR2. This innate-like CD8+ T cell response to SARS-CoV-2 (E)-protein may offer novel opportunities for diagnostic and therapeutic development, warranting further investigation.

IntroductionErgosterol-targeting azoles are widely used in the treatment of Candida albicans infection. In addition to direct antifungal activity, azoles are known to enhance neutrophil-mediated killing of C. albicans, but the underlying mechanisms remain unclear, particularly whether ergosterol depletion directly modulates host immune responses. Gap StatementIt remains unknown whether reduced ergosterol levels alone, independent of broader disruption to sterol biosynthesis and fungal morphogenesis, influence neutrophil antifungal activity. AimThis study aimed to determine how genetic disruption of late-stage ergosterol biosynthesis affects neutrophil-mediated responses to C. albicans. MethodologyDoxycycline-repressible GRACE mutants targeting late-stage ergosterol biosynthesis genes (ERG4, ERG5, ERG3 and ERG28) were co-incubated with primary human neutrophils. Fungal survival, oxidative burst, phagocytosis, neutrophil extracellular trap (NET) formation and cell wall composition were assessed. ResultsAll ergosterol-deficient strains induced elevated neutrophil reactive oxygen species (ROS) production; however, only ERG4 depletion was associated with enhanced fungal clearance. This phenotype correlated with increased phagocytosis and reduced NET formation. Cell wall analysis revealed no changes in total chitin or mannan content but demonstrated significantly increased surface exposure of {beta}-1,3-glucan in ERG4-depleted cells. ConclusionThese findings indicate that disruption of late-stage ergosterol biosynthesis, particularly via ERG4, enhances neutrophil antifungal responses and is associated with increased {beta}-glucan exposure. This study highlights a potential role for ergosterol in immune evasion and suggests that targeting terminal steps of the pathway may improve host-mediated clearance of C. albicans.

Systemic lupus erythematosus (SLE) is associated with infection susceptibility and altered innate immune function. Monocyte metabolism is linked to appropriate cytokine release and bacterial containment. We investigated cytokine production and metabolic programming in the monocyte population from SLE patients and healthy controls following lipopolysaccharide (LPS) stimulation. SLE monocytes displayed increased IL-10, TNF, and IL-8 production, with impaired IL-1{beta} induction. Metabolic profiling revealed altered substrate use, with increased glucose dependence and reduced fatty acid and amino acid oxidation after LPS stimulation. SLE patients exhibited reduced numbers of classical monocytes, expansion of intermediate monocytes, and dysregulated subset-specific metabolic reprogramming in response to LPS. This descriptive study provides a cornerstone for (i) understanding infection susceptibility in SLE, (ii) subset-resolved immunometabolic profiling as a tool in autoimmunity, and (iii) developing future metabolic-targeted therapeutic strategies HighlightsO_LIDescriptive mapping shows SLE monocytes are proinflammatory with glucose dependence after LPS C_LIO_LIClassical and intermediate SLE subsets show divergent baseline metabolic preferences versus healthy C_LIO_LISLE subsets display aberrant LPS responses, i.e.. increased glucose and reduced fatty acid oxidation C_LIO_LIThis study provides a cornerstone for subset-resolved immunometabolism in infection susceptibility. C_LI

The study investigated the interaction between estrogen deprivation and periodontitis, systemically, in the bone marrow, and locally in periodontal tissues using a mouse model. MethodsWe used the ligature-induced periodontitis (LIP) model concurrently with ovariectomy-induced estrogen deprivation. Bone marrow was assessed for myeloid cell proportion by flow cytometry. The femur metaphysis was examined histologically and by micro-CT. Cytokine responses of CD11b+ myeloid cells to lipopolysaccharide stimulation were investigated ex vivo across ovary-intact (Sham), ovariectomized (OVX), and estrogen-replaced (OVX+E2) mice with or without periodontitis. Estrogen-related alterations in periodontitis, including microbiome composition and transcriptomic changes in the gingiva and dentoalveolar complex, were investigated by 16S rRNA sequencing and bulk RNA sequencing, respectively. ResultsOvariectomy increased osteoblast-like and adipocyte-like cell numbers in femoral marrow, whereas LIP reduced both populations (p = 0.020 and p = 0.029, respectively). LIP increased the bone marrow CD45+ hematopoietic fraction in Sham mice. LPS-stimulated bone marrow CD11b+ cells from OVX mice showed lower Tnf, Ccl2, and Il10 expression than Sham mice (p = 0.003, p = 0.005, and p = 0.001, respectively). OVX exacerbated LIP-associated alveolar bone loss, reducing BV/TV (p = 0.003) and increasing osteoclast numbers (p = 0.012). Neither OVX nor E2 replacement significantly altered ligature-associated microbial composition in 16S rRNA sequencing. Bulk RNA sequencing demonstrated estrogen-responsive transcriptomic changes in both the gingiva and dentoalveolar complex, including OVX-associated gene-expression changes that returned toward Sham levels in OVX+E2 mice. These included genes related to stromal regulation (Acan, Igfbp3, Erbb3) and immunity (Gp2, Spib, B2m). ConclusionPeriodontitis and estrogen deprivation exert combined effects on the bone marrow niche. Estrogen deprivation modulates immune- and healing-related gene expression in the gingiva and remaining dentoalveolar tissues during periodontitis.

Behcets disease (BD) is a systemic inflammatory disease. It is considered as an autoinflammatory disease triggered by innate immunity rather than adaptive immunity. Human leukocyte antigen-B51 (HLA-B51) is the strongest genetic factor associated with BD. This study investigated how HLA class 1 molecules interact with innate immune cells and induce cytokine secretion. For this purpose, 293T cells transfected with a plasmid encoding HLA-B51 were cultured with natural killer (NK) cells obtained from healthy human donors. Within 24 h, the concentrations of interleukin-4 (IL-4), IL-8, and interferon-{gamma} (IFN-{gamma}) in the medium increased, indicating that NK cells secreted cytokines without undergoing cellular expansion for cytolysis. NK cells stimulated by nonself HLA-B51 produced IFN-{gamma} levels comparable to those produced by NK cells stimulated by self HLA-B51. NK cells carrying HLA-B51 were accurately recognized by overexpressing HLA-B51 on 293T cells. Moreover, ample intracellular IFN-{gamma} levels were detected in NK cells after stimulation with phorbol 12-myristate-13-acetate (PMA) plus ionomycin. KLRK1 (CD314)-positive cells mainly primarily accounted for IFN-{gamma}-producing cells, whereas KLRK1-negative cells did not. In contrast, both NCR1 (CD335)-positive and -negative cells contributed to IFN-{gamma} production. We next investigated whether HLA-B51 on the surface of 293T cells stimulates KLRK1 as a ligand causing IFN-{gamma} secretion. In masking experiments using anti-KLRK1 antibodies, NK cells with high levels of cell surface KLRK1 decreased the production of IFN-{gamma}. Conversely, human NK cell line KHYG1 cells also produced IFN-{gamma} in culture with 293T cells, but did not increase IFN-{gamma} through HLA-B51 stimulation. The mRNA expression of the signal adaptor protein HCST (DAP10) in KHYG1 cells was lower than that in NK cells, whereas the relative expression of IL-2RA in KHYG1 cells was higher than that in NK cells. These findings suggest that HLA-B51 can interact with KLRK1 on the NK cells inducing IFN-{gamma} secretion, whereas IL-2 signals outweigh HLA-51 stimulation in KHYG1 cells.

Innate immunity and innate immune cell death provide a critical first line of defense against disease. However, excess cell death leads to pathological inflammation. ZBP1 is an innate immune sensor that is central to this balance between defense and inflammation as a driver of inflammatory lytic cell death, PANoptosis. Activation of ZBP1-dependent PANoptosis downstream of diverse triggers has roles in both host defense and disease pathology, making ZBP1 an attractive therapeutic target. Therefore, understanding the distinct roles of ZBP1 in different cell types, organ systems, and tissues is critical to identify therapeutic strategies. Although ZBP1 regulates PANoptosis in multiple cell types, there are limited tools to interrogate its function in a cell type-specific manner. Here, we report the generation of a Zbp1-floxed mouse line (Zbp1fl/fl) for investigation of ZBP1 in distinct cell populations. We crossed Zbp1fl/fl mice to LysMcre mice to selectively deplete Zbp1 from the myeloid compartment, which did not alter immune homeostasis. Bone marrow-derived macrophages (BMDMs) from Zbp1fl/fl mice had normal ZBP1 expression and PANoptosis activation, while those from Zbp1fl/flLysMcre mice exhibited markedly reduced ZBP1 expression and were biochemically and functionally protected from ZBP1-driven PANoptosis; these effects were validated using known triggers of the ZBP1-PANoptosome--IAV, nuclear export inhibition plus IFN, and ethanol. These findings demonstrate this new Zbp1fl/fl mouse as a versatile tool that can be utilized with a variety of Cre-drivers to study ZBP1 in a wide array of distinct cell types. Given the critical role of ZBP1 in disease, this tool will inform the development of therapeutic strategies.

Abstract Background: Mean platelet volume (MPV) is a simple, low-cost biomarker that reflects platelet activation. Its prognostic value in septic shock remains controversial. We aimed to determine whether MPV at intensive care unit (ICU) admission is associated with hospital mortality in patients with septic shock. Methods: Retrospective cohort study of consecutive adults with septic shock (Sepsis-3 criteria) admitted to a single ICU. MPV, severity scores (SOFA, APACHE II, SAPS II), procalcitonin, and clinical data were collected. The primary outcome was in-hospital mortality. Spearman correlation, univariate and multivariate logistic regression (with Firth's correction), ROC curves, and subgroup analyses were performed. Results: Fifty-eight patients were included; mortality was 58.6%. MPV did not differ between non-survivors and survivors (13.09 {+/-} 1.37 vs. 12.66 {+/-} 1.45 fL, p = 0.259). MPV showed a weak correlation with procalcitonin ({rho} = 0.394, p = 0.002) but not with severity scores. In multivariate analysis adjusting for age, sex, SOFA and comorbidity count, MPV was not an independent predictor of mortality (OR 1.075, 95% CI 0.682-1.755, p = 0.749). The area under the ROC curve for MPV was 0.598 (95% CI 0.444-0.752), significantly lower than that of SOFA (0.837) and procalcitonin (0.836). Subgroup analyses showed no significant association between MPV and mortality in any stratum. Conclusions: In this cohort of septic shock patients, MPV at ICU admission was not associated with hospital mortality and had poor discriminative ability. Widely used severity scores and procalcitonin remain superior prognostic markers. MPV should not be used as a prognostic tool in septic shock. Keywords: Septic shock, Mean platelet volume, Mortality, SOFA, Procalcitonin, Biomarker

IgA nephropathy (IgAN) is a common primary glomerulonephritis characterized by glomerular immune-complex deposits with (co)dominant IgA. These deposits are enriched for IgA1 glycoforms with some O-glycans deficient in galactose (Gd-IgA1). Circulating Gd-IgA1 is bound by IgG autoantibodies to form immune complexes, some of which deposit in glomeruli. Genomic and immunologic studies indicate involvement of pro-inflammatory signaling pathways in the production of Gd-IgA1 in IgAN. Genomic studies identified multiple genetic loci associated with IgAN and suggested a convergence on the NF-{kappa}B pathway, including RELA, the gene encoding the NF-{kappa}B subunit p65. However, the mechanisms by which NF-{kappa}B pathways may affect O-glycosylation in IgA1-producing cells are unknown. Using EBV-immortalized B cells derived from peripheral-blood mononuclear cells of IgAN patients and healthy controls that have constitutively activated NF-{kappa}B, we report that inhibition of NF-{kappa}B/p65 by a selective IKK{beta} inhibitor TPCA-1 reduced phosphorylation of NF-{kappa}B/p65 at S536 and decreased production of IgA1 and, conversely, increased Gd-IgA1 production. This was likely related to reduced expression of C1GALT1 gene that encodes the enzyme responsible for galactosylation of IgA1 O-glycans. Flow-cytometry imaging revealed changes in nuclear translocation and co-localization of the NF-{kappa}B/p65 with co-transcriptional factor SP1, a transcriptional activator of C1GALT1, suggesting that NF-{kappa}B pathway affects IgA1 O-glycosylation via SP1 transcriptional control of C1GALT1 expression. Furthermore, prolonged IKK{beta} inhibition altered B cell subpopulations, enhancing generation of cells with a plasmablast-like phenotype, characterized by high SSC MFI and CD138 expression. Together, these findings provide functional evidence for involvement of NF-{kappa}B/p65 and its transcriptional partners in IgA1 O-glycosylation. HighlightsO_LIIKK{beta} inhibition reduced C1GALT1 expression and thereby increased galactose-deficient IgA1 (Gd-IgA1) production in immortalized human B cells. C_LIO_LISP1+ subpopulations, a transcriptional activator of C1GALT1, declined after sustained NF-{kappa}B inhibition. C_LIO_LINF-{kappa}B inhibition shifted a subpopulation of B cells into a plasmablast-like phenotype. C_LIO_LIThis study links NF-{kappa}B signaling with the GWAS-identified RELA susceptibility locus and IgA1 O-glycosylation. C_LI

Chronic lymphocytic leukemia (CLL) is a lymphoid neoplasm with very heterogeneous clinical and biological behavior. Among molecular variables, TP53 alterations are well-established adverse prognostic markers; however, MYC activation, which has been linked to disease progression, has not been completely defined in terms of clinical and biological impact, particularly in relation to TP53 status. Here, we investigated the effects of MYC overexpression according to TP53 status using clinical and transcriptomic data from CLL patients and novel cellular models. CLL patients with TP53WT and MYC overexpression exhibited significantly shorter time to first treatment and overall survival, indicating an aggressive disease course comparable to that of patients with TP53 alterations. Consistently, MYC overexpression in in vitro TP53WTmodels was associated with increased proliferation, enrichment of AKT/mTOR signaling and upregulation of genes involved in leukemogenesis and tumor progression such as FOXO6. Moreover, MYC overexpression was associated with increased sensitivity to venetoclax in TP53WT cells. By contrast, the concurrence of MYC overexpression and TP53 dysfunction conferred resistance to conventional CLL therapies such as BCL2 or BTK inhibitors. Of note, we identified a glycolysis inhibitor, in monotherapy or combined with BKT inhibitors, as a potential therapeutic strategy for CLL patients harboring MYC overexpression and TP53 alterations.

Haemophagocytic lymphohistiocytosis (HLH) is a rare, life-threatening hyperinflammatory syndrome characterised by uncontrolled immune activation. Reduced high- and low-density lipoprotein cholesterol and hypertriglyceridaemia are reported in HLH, suggesting lipid metabolism disturbances although in-depth serum metabolomic analysis is lacking in HLH. Here a lipid-focused NMR spectroscopy platform was used to define the serum metabolomic landscape of adults hospitalised with HLH compared to adults with sepsis (HLH-mimic) and rheumatic disease (potential HLH drivers/triggers), following surgical resection of solid organ cancer (non-infectious acute inflammation controls) and healthy controls (HCs). Serum metabolites distinguished HLH from HCs with high accuracy (>91.36%) using multiple machine learning models. The top classifying features included elevated apolipoprotein-B (ApoB)-containing low, intermediate, and very low-density lipoprotein particles; and lipoprotein remodelling towards triglyceride enrichment and cholesterol depletion. Differentially abundant metabolites in HLH compared to all control groups were enriched in pathways related to lipid metabolism including: 'Lipid particles composition', 'Plasma lipoprotein clearance', 'Plasma lipoprotein remodelling', 'Glucose homeostasis' and 'Amino acid metabolism'. Metabolomic results were validated using matched whole blood RNA-sequencing which identified differentially expressed genes enriched in metabolic modules associated with lipid, amino acid, and glucose metabolism, supporting a coordinated metabolic dysregulation in HLH from a transcriptomic to metabolomic level. Finally, twenty-seven metabolites including ApoB-containing, triglyceride-rich lipoproteins and saturated fatty acids distinguished HLH from all disease controls (AUC>0.70) either alone or combined as a metabolomic signature. Elevated ApoB and ApoB:ApoA1 ratio in HLH vs sepsis and HCs were validated by ELISA, supporting their utility as biomarkers to distinguish HLH from other hyperinflammatory syndromes.

Sarcoidosis is a multisystem disorder that primarily affects the lungs and is characterizedby granulomatous inflammation. However, much of the underlying disease mechanisms remain poorly understood. Extracellular vesicles (EVs) are small membrane-bound particles released by all cells and carry various cargos including metabolites. They are involved in intercellular communication that can be dysregulated in diseases.This study characterizes the metabolic cargo of EVs isolated from bronchoalveolar lavage fluid (BALF), using liquid chromatography-mass spectrometry (LC-MS)-based metabolomic analysis, in patients with sarcoidosis (n=37), compared to healthy controls (n=10). Additionally, the sarcoidosis signature was compared to another pulmonary disorder, anti-synthetase syndrome (ASyS, n=10). Arachidonic acid (AA) results were verified by ELISA. A total of 1202 metabolites were detected, with 111 annotated ones further analyzed. EVs from sarcoidosis patients showed distinct metabolomic profiles compared to both ASyS patients and healthy controls, with 38 annotated metabolites differentially expressed in any of the groups. In both annotated and non-annotated data, sarcoidosis patients clustered separately from ASyS patients and healthy individuals. Furthermore, sarcoidosis patients clustered in 3 subgroups, whereof one was similar to ASyS patients and one stood out as showing higher cell counts in BALF. Higher AA levels were found in sarcoidosis patient EVs by LC-MS, and AA results were verified by ELISA. Our data show that BALF EV metabolites are disease-dependent and support the notion thatsarcoidosis patients should be further subgrouped for better diagnosis and treatment.