Search Results (353)

High-altitude pulmonary edema (HAPE) is a rapidly progressive, life-threatening disorder arising in otherwise healthy individuals upon ascent to high altitude, yet the mechanisms underlying maladaptive vascular leak remain poorly defined. Although elevated pulmonary arterial pressure and capillary stress failure are recognized as central hemodynamic drivers, accumulating evidence indicates that innate immune dysregulation is an equally critical, largely unexplored determinant of HAPE. To systematically delineate the immune and molecular programs that distinguish pathological responses to hypobaric hypoxia from acclimatization, peripheral blood along with clinical details was collected from low-altitude controls (LA-Cntrl, number of participants, (n = 19), healthy high-altitude sojourners (HA-Cntrl, n = 47), and HAPE patients (n = 90). Plasma proteomic markers were quantified using a targeted panel, while monocyte and dendritic cell subsets in peripheral blood mononuclear cells were immunophenotyped by multicolor flow cytometry. HA-Cntrl subjects displayed an anti-inflammatory profile, marked by the suppression of CXC chemokine receptor 3 axis chemokines. HAPE patients, in contrast, exhibited a pro-inflammatory, vascular injury signature, with elevated levels of inflammatory interleukins and myeloid and chemotactic factors. This inflammatory signature was accompanied by the expansion of classical monocytes, implicating a myeloid vascular program associated with HAPE. Full article

Hepatic inflammation is a defining feature of Metabolic Dysfunction-Associated Steatohepatitis (MASH), yet the specific contributions of individual immune cell populations and their reciprocal interactions remain incompletely understood. In this study, we combined flow cytometry with single-cell transcriptomic profiling to characterize the hepatic immune landscape in a novel model of spontaneous MASH caused by hepatocyte-specific deficiency of endoplasmic reticulum-associated degradation (ERAD). Hepatic ERAD deficiency led to the expansion of multiple immune cell populations in the liver, including CD8+ T cells, macrophages, monocytes, and dendritic cells, accompanied by extensive functional reprogramming of both innate and adaptive immune compartments. Myeloid cells exhibited enhanced phagocytic activity and increased antigen processing and presentation, whereas CD8+ T cells displayed elevated proliferation capacity, DNA repair activity and cytotoxicity. Notably, two functionally distinct triggering receptor expressed on myeloid cells 2 (TREM2)-expressing macrophage subsets emerged during the progression of ERAD deficiency-induced MASH. Depletion of CD8+ T cells increased monocyte infiltration and aggravated liver injury, suggesting that CD8+ T cells exert a previously unrecognized protective role by restraining monocyte recruitment. Collectively, these findings reveal highly coordinated interactions between innate and adaptive cells during MASH progression and identify CD8+ T cells as potential regulators of monocyte infiltration and hepatic injury. Full article

Neurologic manifestations of long COVID, also called neurologic post-acute sequelae of SARS-CoV-2 infection (Neuro-PASC: NP) include persistent alteration of cognitive functions. We investigated whether these could be driven by immune perturbations. We combined flow cytometry (FC), sleep profiling, and single-cell RNA sequencing of peripheral blood immune cells from older adult (>55 years) individuals with and without NP to evaluate relationships with objective cognitive performance. NP participants showed reduced numbers of blood monocytes with increased mitochondrial superoxide, indicating an altered monocyte mitochondrial redox state. Higher peripheral capillary oxygen saturation (SpO₂) was associated with better processing speed in NP participants. Monocyte transcriptional analyses identified mitochondrial adenosine triphosphate (ATP) synthase/Complex V (Complex V) pathway associated with cognitive performance in people without NP; this coupling was abrogated in NP patients, in whom cognitive performance instead showed an opposite relationship with Complex V. Shared leading-edge genes defined a 13-gene monocyte anchor representing this cognition-associated NP phenotype. Higher anchor scores were associated with coordinated oxidative phosphorylation and cytotoxic programs across CD3⁺ T-cell subsets in individuals without NP, but not in NP participants. T-cell receptor stratified analyses showed that this altered relationship occurred in both expanded and unexpanded T-cell populations. FC correlations also supported reduced monocyte-to-lymphocyte mitochondrial coordination in NP. These exploratory findings identify a sleep and cognition-linked monocyte mitochondrial phenotype characterized by altered myeloid–lymphoid immune coordination in NP. Full article

Major airway diseases, including chronic obstructive pulmonary disease (COPD), asthma, bronchiectasis and chronic rhinosinusitis without nasal polyps (CRSsNP), frequently coexist and share inflammatory, epithelial and remodeling features. However, whether these clinically distinct airway disorders are driven by a unified genetic liability and how this shared liability maps to disease-relevant tissues, genes and immune-regulatory programs remain incompletely understood. We integrated GWAS summary statistics for COPD, asthma, bronchiectasis and CRSsNP using linkage disequilibrium score regression, local genetic correlation analysis and Genomic structural equation modeling. A latent shared airway disease factor, termed gAirwayDisease, was constructed to capture common genetic liability across the four conditions. We then applied an integrative functional genomics framework, including gsMap spatial enrichment, PoPS gene prioritization, MAGMA gene-set enrichment, GTEx v8 lung MTWAS, OneK1K and DICE immune-cell MTWAS, scMORE regulon analysis and phenome-wide Mendelian randomization. All six airway disease pairs showed positive genetic correlations, with estimates ranging from 0.508 to 0.685. Genomic SEM supported a single shared factor, with positive standardized loadings for COPD, asthma, bronchiectasis and CRSsNP and excellent model fit. Spatial mapping localized gAirwayDisease-associated signals to airway- and epithelial-associated anatomical domains. PoPS prioritized immune and airway-relevant genes, including SMAD3, GATA3, IL1R1, RUNX3 and STAT6, while MAGMA enrichment highlighted B-cell activation, T-cell activation and transcriptional regulatory pathways. Lung MTWAS identified SLC9A2 and ORMDL3 as top genetically regulated expression signals. OneK1K immune-cell MTWAS highlighted recurrent IL18R1 associations across CD4 and CD8 T-cell subsets. scMORE further identified 36 significant regulon–cell type pairs across dendritic cells, B cells, monocytes, T cells and NK cells, including BCL11A, TCF4, KLF4, RUNX1 and STAT4 regulons. MR-PheWAS linked genetically predicted gAirwayDisease to respiratory, allergic, lung function and immune-related traits. This study defines gAirwayDisease as a genetically informed latent factor capturing shared liability across major airway diseases. Integrated functional genomic analyses highlight airway epithelial and immune regulatory programs associated with shared disease susceptibility and prioritize candidate genes and regulons for future experimental validation. Full article

Background: Accurate identification and classification of white blood cell (WBC) subtypes in peripheral blood smears (PBS) is essential for the diagnosis and monitoring of hematological malignancies, including leukemia. Conventional manual microscopy, although clinically established, is labor-intensive and subject to inter- and intra-observer variability. Deep learning-based object detection offers a route to automation, yet most prior studies are limited by small datasets, restricted cell taxonomies, or single-microscope acquisition. This study evaluates a YOLOv11-large (YOLOv11L) detector for simultaneous localization and classification of 13 leukemia-relevant WBC subtypes plus an artifact class (14 classes total), trained on the large-scale, multi-domain, open-source LeukemiaAttri dataset. Methods: From the LeukemiaAttri dataset, 18,664 annotated images (67,347 objects) acquired at 40× and 100× magnification were partitioned by stratified sampling into training (70%), validation (15%), and test (15%) sets. The training set was expanded to 65,785 images through extensive geometric, photometric, and AugMix augmentation. A YOLOv11L model pretrained on MS COCO was fine-tuned for 250 epochs (640 × 640 input) on a single NVIDIA H200 SXM GPU, using an auto-selected optimizer (momentum 0.9; weight decay 5 × 10⁻⁴), automatic mixed precision (AMP), and mosaic augmentation for the first 240 epochs. Results: On an internal held-out test set, the model achieved an mAP50 of 93.9%, mAP50-95 of 77.9%, precision of 94.1%, recall of 88.8%, and an F1 score of 0.913, with similar performance in the validation and test sets. Class-wise average precision (AP) ranged from 89.3% (monocyte) to 98.2% (monoblast), confirming consistent detection across morphologically diverse subtypes. Conclusions: The YOLOv11L detector achieved high performance across all 14 categories on the internal test set, with metrics exceeding those previously reported for subset-specific baselines. These findings support further evaluation of the model as a decision-support tool for peripheral blood smear analysis. External validation is required to determine its clinical utility and generalizability. Full article

Primary membranous nephropathy (pMN) is an antibody-mediated podocytopathy, most commonly caused by autoantibodies against the M-type phospholipase A2 receptor (PLA2R1). Rituximab (RTX), an anti-CD20 monoclonal antibody, is a first-line treatment for moderate-to-high-risk pMN, inducing partial or complete remission in about 60% of patients within 24 months. However, treatment response varies considerably, and current biomarkers, including anti-PLA2R1 titers and peripheral B cell counts, have limited predictive value for non-response or relapse. Beyond B cell depletion, RTX exerts broader immunomodulatory effects by influencing T cell subsets, monocytes, and natural killer (NK) cells involved in antibody-dependent cellular cytotoxicity. This review examines the peripheral immune cell changes that accompany anti-CD20 therapy and their value as candidate biomarkers. Total CD19+ B cell depletion is the standard pharmacodynamic measure of drug effect but correlates only loosely with clinical outcome. A specific B cell reconstitution profile was associated with pending relapse. Class-switched memory B cells remain depleted during sustained remission, and their premature re-expansion has been associated with subsequent relapse. Regulatory T cells are reduced in active disease and rise within days of infusion in patients who later respond. The systemic inflammation response index, derived from the routine differential count, has been associated with both 6- and 12-month remission. These observations derive from small, mostly single-center cohorts using heterogeneous panels and different RTX regimens. On the available evidence, immune cell profiling cannot yet be recommended for routine disease monitoring, and larger prospective studies with standardized panels are required. Full article

Background: Osteosarcoma (OS) is a devasting bone cancer that occurs primarily in pediatric patients, and pet dogs, and treatment options have not advanced in decades. There is a profound need for advancement of treatment options to improve patient prognosis given the grim 70% 5-year survival rate for human patients, and 10–12-month median survival for canine patients. A major hurdle in advancing treatment options is overcoming the immunosuppressive tumor microenvironment to mitigate metastatic disease progression—the leading cause of mortality in OS patients. Methods: We investigated the ability of a mechanical focused ultrasound ablation modality, histotripsy, to induce acute immunomodulation in canine patients with spontaneously occurring OS. Results: Immunomodulation was evident locally and systemically. Tumor gene signatures indicated upregulation of pro-inflammatory signaling pathways and T-cell receptor signaling, and B-cell activation, and systemically, increased monocyte activation was observed within 5 days post-histotripsy ablation. A subset of patients who received histotripsy prior to definitive standard-of-care exceeded the reported expected median survival time of 10–12 months for canine OS patients that received definitive standard-of-care only. Conclusions: Our results demonstrate the promising potential of histotripsy to overcome the immunosuppressive tumor microenvironment. Full article

Metabolic dysfunction-associated steatohepatitis (MASH) is a progressive immunometabolic liver disorder involving lipid dysregulation, inflammation, fibrosis, and extrahepatic immune–neural responses, yet therapies capable of modulating these interconnected processes remain limited. Berberine (BBR), an isoquinoline alkaloid derived from traditional medicinal plants including Coptis chinensis Franch. (Coptidis Rhizoma), has shown metabolic and anti-inflammatory activities; however, its effects on hepatic inflammation and the liver–brain inflammatory axis in MASH remain unclear. Here, network pharmacology and molecular docking were used to predict BBR targets and pathways, followed by in vivo validation in a methionine- and choline-deficient diet-induced mouse model. Liver injury and metabolic alterations were assessed using serum biochemistry and lipid profiles, histological changes by hematoxylin and eosin and Sirius Red staining, and hepatic and hypothalamic inflammation by qRT-PCR, flow cytometry, and Iba-1/GFAP immunostaining. SREBF1, AKT1, and TGFB1 were identified as core BBR targets, with pathways linked to lipid metabolism, oxidative stress, inflammation, and fibrogenesis. BBR attenuated liver injury, steatosis, steatohepatitis, and fibrosis, suppressed SREBF1-associated lipogenic signaling and fibrogenic gene expression, remodeled circulating monocyte subsets, reduced Kupffer cell accumulation, and inhibited hypothalamic microglial activation. These findings suggest that BBR alleviates MCD-induced steatohepatitis through multi-target regulation of hepatic metabolic dysfunction, immune remodeling, and hypothalamic neuroinflammation. Full article

Background/Objectives: Heart failure with reduced ejection fraction (HFrEF) involves coexisting inflammatory and hemostatic dysregulation contributing to thromboembolic and bleeding risk. Ten-eleven translocation (TET1-3) proteins regulate immune-cell phenotype, but their relationship to plasma coagulation parameters in HFrEF is poorly defined. We aimed to determine whether TET1-3 protein expression in peripheral blood leukocyte subpopulations is associated with routinely available plasma coagulation parameters in HFrEF, and whether associations differ by direct oral anticoagulant (DOAC) exposure and clinical phase. Methods: In this cross-sectional, observational, two-center study, 107 patients with HFrEF were enrolled (39 receiving a DOAC, non-randomized; 68 not receiving a DOAC, of whom seven received a vitamin K antagonist and 61 received no oral anticoagulant). TET1-3 protein expression was assessed by flow cytometry in T lymphocytes, B lymphocytes, natural killer (NK) cells, monocytes, and granulocytes, expressed as the ratio of test-to-negative-control geometric mean fluorescence intensity. Associations with activated partial thromboplastin time (aPTT) and international normalized ratio (INR) were analyzed using nonparametric tests and Spearman correlations; DOAC samples were drawn at steady-state trough. Results: DOAC-treated patients constituted a distinct clinical subgroup (older, predominantly AF/AFL) and showed longer aPTT and higher TET expression in selected immune-cell subsets; these between-group differences cannot be attributed to DOAC therapy. Patients with aPTT at or above the median showed higher TET expression in T cells, B cells, NK cells, and selected leukocyte indices, whereas INR-based stratification did not. In continuous analyses, TET indices showed multiple moderate positive Spearman correlations (R = 0.25–0.49) with both aPTT and INR—with INR showing the strongest single association—and no associations with composite inflammatory indices (NLR, SII, SIRI); all comparisons were exploratory and uncorrected for multiplicity. Associations appeared stronger in stable than in worsening HFrEF (exploratory). Conclusions: Peripheral leukocyte TET protein expression was associated with plasma coagulation parameters in HFrEF; the aPTT-specific pattern was confined to the categorical (median-split) analysis, whereas continuous analyses showed associations with both aPTT and INR. Because of the cross-sectional design, moderate sample size, and potential confounding by indication, these findings should be considered hypothesis-generating. TET-related immune-cell phenotyping may capture a non-redundant immune–coagulation signal in HFrEF and warrants prospective validation. Full article

Fine particulate matter (PM2.5) is an air pollutant that significantly impacts environmental and health outcomes. In Chiang Mai province, Thailand, residents face recurring PM2.5 pollution from November to May each year, primarily due to open biomass burning and transboundary emissions. The long-term health impacts of PM2.5 in Chiang Mai remain inadequately documented. This study aims to investigate leukocyte distribution and IgE level in response to long-term PM2.5 exposure. Participants residing in San Patong district, Chiang Mai, were recruited. Leukocyte distribution was investigated by the complete blood count and flow cytometry. IgE levels were measured by sandwich enzyme-linked immunosorbent assay. Long-term PM2.5 exposure is associated with significant changes in leukocyte distribution, including WBC count, neutrophil, monocyte, and basophil absolute count, while lymphocyte and eosinophil counts were not significantly affected. In the present study, flow cytometric immunophenotyping was performed during the late PM2.5 season to evaluate the distributions of major leukocyte populations and the expression of activation and inhibitory markers on lymphocyte subsets. Interestingly, IgE levels showed a decreasing trend. These findings highlight the immunological effects of repeated PM2.5 exposure and underscore the need for further research to clarify its mechanisms and health implications. Full article

Background/Objectives: Colorectal liver metastases (CRLMs) are a major contributor to recurrence and mortality in colorectal cancer (CRC), with approximately a quarter of patients developing liver metastases over the course of the disease. Bone-marrow-derived myeloid lineages are sent into the circulatory system and colonize pre-metastatic niches, yet the transcriptional programs by which they establish a pro-metastatic microenvironment remain incompletely defined. Methods: Using an MC38 splenic-injection CRLM mouse model, we generated single-cell RNA sequencing (scRNA-seq) profiles of FACS-sorted CD11b⁺Gr1⁺ bone marrow myeloid cells, together with bulk RNA sequencing profiles of bone marrow and peripheral blood. Downstream analyses were performed in silico, including clustering and annotation, trajectory inference, cell–cell communication analysis, weighted gene co-expression network analysis (WGCNA), and pathway enrichment, with subset specificity examined against a public dataset of E. coli (Escherichia coli)-infected mice. Results: Within the CD11b⁺Gr1⁺ compartment, a CCR2⁺ neutrophil-like population (Ly6g⁺S100a8/9⁺) emerging during terminal differentiation was identified, which was enriched in CRLM mice but nearly absent in controls. Communication inference revealed an FN1-CD44 interaction involving mature neutrophils, which was associated with an epithelial–mesenchymal transition signature and upregulation of Tgfb1 and Il1b. This subpopulation was not recovered in the infection dataset, suggesting relative specificity to CRLMs. Conclusions: Within the constraints of a splenectomized hepatic colonization model, integrated transcriptomic analysis highlighted a CCR2⁺ bone marrow neutrophil-like population as a candidate contributor to CRLM, challenging the view that CCR2⁺ pro-metastatic myeloid cells are exclusively monocytic and suggesting candidate biomarkers and therapeutic targets for further study. Full article

Porcine circovirus type 2 (PCV2) and Mycoplasma hyopneumoniae (Mhp) are major contributors to the porcine respiratory disease complex. Although PCV2-Mhp bivalent inactivated vaccines are useful for simultaneous disease control, their immunogenicity may be improved by adjuvant optimization. This study evaluated a composite adjuvant consisting of porcine interleukin-2 (IL-2), IL-4, IL-6 and MnJ(beta), a colloidal manganese adjuvant, in an initial murine immunogenicity model. Thirty female Kunming mice were assigned to three groups (n = 10/group): bivalent antigen plus IL-2/IL-4/IL-6/MnJ(beta), bivalent antigen plus MnJ(beta), or phosphate-buffered saline. Body weight, complete blood count, peripheral blood T- and B-cell subsets, PCV2-specific IgG and Mhp-specific indirect hemagglutination titers were monitored after primary and booster immunization. The composite formulation did not suppress body-weight gain or induce sustained abnormalities in erythrocyte- or platelet-related indices. WBC, neutrophil, lymphocyte and monocyte counts were elevated in group A at days 7 and 28 post-primary immunization, indicating transient immune activation. Day-56 flow cytometry indicated increased CD19+IgM-IgD- B-cell and effector/memory T-cell-associated responses. PCV2-specific IgG increased from day 14 onward. At day 56, the OD450 value in group A reached 1.532 ± 0.006, compared with 1.095 ± 0.004 in group C1 and 0.102 ± 0.002 in group C2, corresponding to approximately 1.40-fold and 15.09-fold higher levels than the MnJ(beta)-adjuvanted and PBS control groups, respectively. Mhp-specific IHA titers were also maintained at high levels after booster immunization; at day 56, group A showed a log2 endpoint titer of 13.00 ± 0.00, corresponding to a GMT of 1:8192, whereas group C1 showed a log2 endpoint titer of 12.00 ± 0.00, corresponding to a GMT of 1:4096, and group C2 remained negative. These results indicate that the IL-2/IL-4/IL-6/MnJ(beta) composite adjuvant demonstrates potential for improving antibody and peripheral lymphocyte responses to PCV2-Mhp bivalent antigen, but protective efficacy must be confirmed in target-species challenge studies. Full article

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of immature myeloid cells that accumulate in cancer and represent one of the major drivers of tumor-associated immunosuppression. MDSCs actively contribute to tumor progression by inhibiting both innate and adaptive immune responses, promoting angiogenesis, metastatic dissemination, and resistance to immunotherapy. Two major subsets have been identified, polymorphonuclear (PMN-) and monocytic (Mo-) MDSCs, each characterized by distinct phenotypic, metabolic, and suppressive properties. Within the tumor microenvironment (TME), MDSCs establish a complex network of interactions with T-, B-, NK-cells, dendritic cells, and macrophages, thereby orchestrating immune escape and tumor persistence. Recent evidence highlights the pivotal role of metabolic rewiring in regulating MDSC survival and suppressive activity. Enhanced aerobic glycolysis, fatty acid oxidation, amino acid depletion, reactive oxygen species (ROS) production, and adenosine metabolism collectively sustain MDSC-mediated immune dysfunction and shape the immunosuppressive TME. In particular, the crosstalk between PMN-MDSCs and NK cells has emerged as a critical mechanism of tumor immune evasion, leading to impaired NK cell cytotoxicity, altered activating receptor expression, and defective cytokine production. In this review, we summarize the current knowledge on the phenotypic and functional heterogeneity of MDSCs, their metabolic adaptations, and their interactions with immune effector populations in cancer. Furthermore, we discuss emerging therapeutic strategies aimed at targeting MDSC recruitment, differentiation, metabolic pathways, and suppressive functions. Understanding the molecular and metabolic mechanisms governing MDSC biology may provide novel opportunities to overcome tumor-induced immunosuppression and improve the efficacy of current cancer immunotherapies. Full article

Introduction: Cutaneous T cell lymphoma (CTCL), most commonly known as mycosis fungoides (MF), is characterized by an increasingly immunosuppressive tumor microenvironment (TME) as the disease progresses. Cancer-associated fibroblasts (CAFs) are key stromal components that support a permissive niche, in part through the secretion of small extracellular vesicles (sEVs), predominantly exosomes, that mediate intercellular communication. We investigated the immunomodulatory role of exosome-enriched sEVs derived from MF fibroblasts (MF-Fs) compared to normal fibroblasts (N-Fs). Materials and Methods: Primary MF-Fs from early-stage MF biopsies and N-Fs from healthy skin were cultured in vitro. sEVs enriched with exosomes were isolated by ultracentrifugation and characterized by flow cytometry (CD81), electron microscopy, Nanosight analysis, and protein quantification, and their uptake by normal peripheral blood mononuclear cells (nPBMCs) was confirmed using PKH26-labeled sEVs. nPBMCs, monocytes, CD4⁺ and CD8⁺ T cells from healthy donors were exposed to MF-F or N-F sEVs. Cell viability was assessed using MTT and trypan blue exclusion assays. Mass cytometry (CyTOF) profiled immune subsets and regulatory proteins for preliminary observation. Monocyte polarization was evaluated by flow cytometry for M1 (CD80, CD86) and M2 (CD163, CD206) markers and PD-L1 expression; M1/M2-associated cytokines and sEV-microRNAs were quantified by qRT-PCR. Results: Both MF-F and N-F sEVs were internalized by nPBMCs and reduced their viability, with a more pronounced effect observed for MF-F sEVs. In nPBMCs, MF-F sEVs also increased the frequency of M2-like macrophages, decreased M1 polarization, and enhanced PD-L1 expression. In primary monocytes, MF-F- compared with N-F-derived sEVs upregulated M2-associated cytokines (IL-10, TGF-β), increased PD-L1 expression, and generated M2-like cells that suppressed CD4⁺ and CD8⁺ T cell viability. Conclusions: MF-F sEVs promote an immunosuppressive TME and represent potential therapeutic or biomarker targets in MF. Full article

FOXP3 is the master transcriptional regulator of regulatory T cells (Tregs) and is expressed in humans as two main alternatively spliced isoforms: full-length FOXP3 (FOXP3-FL) and the exon 2-deficient variant (FOXP3-Δ2). While the role of these isoforms has been mainly studied in CD4⁺ T cells, their distribution across peripheral blood leukocyte populations and their relationship with immune checkpoint expression remain incompletely defined. In this study, we used a multiparametric flow cytometry panel allowing isoform-specific detection of FOXP3-FL and FOXP3-Δ2, together with PD-1 and CTLA-4, to analyze peripheral blood samples from six healthy donors under basal conditions. Major leukocyte populations, including CD4⁺CD25⁺ and CD4⁺CD25⁻ T cells, CD8⁺ T cells, monocytes, and neutrophils, were evaluated. FOXP3-FL predominated in CD4⁺CD25⁺ T cells, whereas FOXP3-Δ2 was more frequently detected in CD8⁺ T cells, monocytes, and neutrophils. However, the absolute frequencies of these FOXP3-Δ2-positive populations were low, consistent with the overall low levels of FOXP3 expression observed in these cell types. In CD4⁺ T-cell subsets, PD-1 expression was generally higher than CTLA-4, regardless of FOXP3 isoform, and FOXP3-Δ2⁺ cells showed relatively higher PD-1 expression compared to FOXP3-FL⁺ cells. In contrast, checkpoint expression in non-CD4⁺ populations was limited. The observed FOXP3-FL⁺/FOXP3-Δ2⁺ ratios across immune cell populations were consistent with a predominant role of FOXP3-FL in maintaining immune tolerance under basal conditions; whether these patterns are preserved or altered in pathological settings warrants further investigation. These results provide a descriptive overview of FOXP3 isoform distribution and checkpoint expression across peripheral blood immune cell subsets in healthy individuals, which may serve as a reference for future studies in immune-mediated diseases. Full article