This study aimed to investigate the prognostic value of FLT3-ITD molecular features such as allelic ratio (AR), variant allele frequency (VAF), insertion length, insertion number and insertion site in patients with de novo acute myeloid leukemia (AML). Next-generation sequencing (NGS) was used to detect FLT3-ITD mutations in 170 patients with newly diagnosed AML (except acute promyelocytic leukemia). FLT3-ITD patients with longer insertion lengths, higher allelic ratio, and more mutations had relatively shorter overall survival(OS), though not statistically significant. Early transplantation or FLT3 inhibitor therapy led to longer OS and event-free survival(EFS). Insertion sites located in Hinge Region(HR)/β1 domain and juxtamembrane domain (JMD) derived significantly greater benefit from early FLT3 inhibitor therapy(primarily sorafenib), showing significantly prolonged overall survival. HR/β1 insertion and multiple insertions showed a trend toward being risk factors for EFS. While white blood cell count > 30 × 10⁹/L and insertion of FLT3-ITD in the HR/β1 site were independent risk factors affecting patients’ overall survival. Patients with high white blood cell counts and HR/β1 insertions demonstrated shorter overall survival, while early administration of FLT3 inhibitors resulted in significantly prolonged overall survival in this population. Early transplantation and FLT3 inhibitor therapy significantly improved prognosis in AML patients. In the era of FLT3-ITD targeted drug therapy combined with transplantation, the insertion site of FLT3-ITD based on high throughput sequencing results helps predict the efficacy of FLT3 inhibitors. Integrating white blood cell count with HR/β1 insertion site can identify a high-risk patient subgroup likely to benefit from FLT3 inhibitor therapy.

Post-transplant relapse remains a major clinical challenge in Philadelphia chromosome–positive acute lymphoblastic leukemia (Ph + ALL). Real-time quantitative PCR (RQ-PCR) for BCR::ABL1 is the current standard for measurable residual disease (MRD) monitoring, whereas digital PCR (dPCR) offers substantially higher analytical sensitivity. Whether this increased sensitivity translates into additional prognostic value after allogeneic hematopoietic stem cell transplantation (allo-HSCT) remains unclear. In this prospective study (NCT06211166), 270 patients with Ph + ALL were longitudinally monitored after allo-HSCT. MRD was assessed in parallel using dPCR, RQ-PCR, and MFC. Based on the first post-transplant MRD detection pattern, patients were categorized into four groups: double-negative (n = 80), dPCR–single-positive (n = 158), RQ-PCR–single-positive (n = 3), and double-positive (n = 29). The dPCR–single-positive pattern was the most prevalent MRD status, accounting for 58.5

This study aimed to analyze the clinical characteristics and prognostic factors in therapy-related acute myeloid leukemia (t-AML) patients with RUNX1::RUNX1T1 fusion. A retrospective analysis was performed. Twenty-three t-AML patients with RUNX1::RUNX1T1 were included as the case group. Ninety-two de novo AML patients with RUNX1::RUNX1T1 were randomly selected using the case-pair method in a 1:4 ratio who matched for (1) sex, (2) age (± 5 years), (3) time of diagnosis (± 3 years). A total of 115 AML patients with RUNX1::RUNX1T1 were enrolled. The CR rate after two cycles in t-AML patients with RUNX1::RUNX1T1 was same to that in de novo AML patients with RUNX1::RUNX1T1(95.6

OBJECTIVE:To develop a new TaqMan-MGB probe based quantitative real-time polymerase chain reaction (qPCR) assay for primary screening and follow-up monitoring of colony-stimulating factor 3 receptor (CSF3R ) T618I mutation in patients with acute myeloid leukemia (AML) and chronic neutrophilic leukemia (CNL). METHODS:Specific primers and probes were designed using the Primer Express v3.0 software, and plasmid standards were constructed based on the wild-type (CSF3R wt) and mutant (CSF3R T618I) genomic DNA sequences. Standard curve was plotted for the quantitative detection of the hot spot mutation of CSF3R T618I. DNA samples were obtained from 421 AML and 12 CNL patients. RESULTS:A novel qPCR system based on TaqMan-MGB probes for the quantitative detection of the CSF3R T618I mutation was successfully established. The predicted sensitivity level was at least 0.625% for CSF3R T618I mutant allele in a wild-type background. The detection rate of CSF3R T618I mutation in our cohort was 3.33% (14/421) in AML patients and 83.33% (10/12) in CNL patients, which was highly consistent with the results of high-depth target regional sequencing (TRS) and Sanger sequencing. No CSF3R T618I mutation was detected in 20 healthy donors. The mean variant allele frequency (VAF) of CSF3R T618I in mutation-positive CNL patients calculated using the standard curve was (38.90±15.20)%, which was significantly higher than that in mutation-positive AML patients ［(21.72±16.11)%, P =0.015］. CONCLUSION:The innovative TaqMan-MGB probe-based qPCR methodology is a reliable, sensitive, and quantitative assay for the detection of CSF3R T618I mutation in patients with CNL and AML. This approach promises to facilitate the diagnosis of these diseases and enhance the monitoring of therapeutic response.

Blinatumomab, a CD19/CD3 bispecific T-cell engager, is frequently used for B-cell acute lymphoblastic leukemia (B-ALL) prior to allogeneic hematopoietic stem cell transplantation (allo-HSCT). Although its efficacy in achieving measurable residual disease negativity is well established, its profound B-cell depletion and potential immunomodulatory effects may exacerbate post-transplant viral reactivation risks, particularly in the context of the inherent immunosuppression associated with allo-HSCT. In this matched retrospective cohort study, we identified 97 consecutive B-ALL patients who received blinatumomab prior to allo-HSCT between January 2021 and December 2024. Using 1:2 propensity score matching based on gender, age, and pre-transplant chemotherapy regimen, we selected 194 control patients from the same period who underwent allo-HSCT without prior blinatumomab exposure. Clinical outcomes were compared between the two cohorts. By day 100, EBV viremia incidence was significantly higher in the blinatumomab group (41.5

Background We aim to investigate whether the myelodysplastic syndrome stem cell (MDS-SC)-based assay could be used to predict relapse and survival after treatment in patients with MDS with excess blasts (MDS-EB). Methods A total of 143 cases receiving allografting were prospectively enrolled. A single-cell proteogenomic technique was used to evaluate the characteristics of CD34 + MDS subsets. These cells were detected using multiparameter flow cytometry (MFC) at diagnosis and post-treatment. Results The MDS-SCs could be detected based on CD34 + CD38 − cocktail + immunophenotype by MFC, which exhibit greater stemness and quiescence than CD34 + CD38 − CD33 + MDS cells, CD34 + CD38 − CD45RA + MDS cells, and CD34 + CD38 − CD123 + MDS cells. A high-level of CD34 + CD38 − cocktail + MDS-SCs (≥ 0.1064%) before allograft independently predicted 3-year cumulative incidence of relapse (CIR, P < 0.001). No association of MDS cells evaluated by the traditional MFC method before transplantation with relapse was observed. Patients with positive CD34 + CD38 − cocktail + MDS-SCs (≥ 0.0081%) after allografting experienced a higher 3-year CIR (40.4% vs. 6.5%, P < 0.001) and lower disease-free survival (DFS, 57.4% vs . 85.1%, P < 0.001) than those with negative CD34 + CD38 − cocktail + MDS-SCs (< 0.0081%). Multivariate analysis revealed that positive CD34 + CD38 cocktail + MDS-SCs after transplantation independently predicted the CIR ( P < 0.001) and DFS ( P < 0.001). Patients with traditional MFC MRD positivity after allografting also had a higher CIR (60.0% vs. 12.8%, P < 0.001) and lower DFS (40.0% vs. 80.2%, P < 0.001) than those with negative results. Compared with the traditional MFC method, the MDS-SC-based assay has higher sensitivity and C-index for disease burden determination and MRD detection. Conclusions Our data suggest the superiority of the MDS-SC-based assay over the traditional MFC method for outcome prediction in MDS-EB patients.

Gastrointestinal acute graft-versus-host disease (GI aGVHD) remains a major complication after allogeneic haematopoietic stem cell transplantation (allo-HSCT), and early risk identification and intervention are essential for improving outcomes. Mucosal-associated invariant T (MAIT) cells are mucosa-enriched unconventional T cells with major histocompatibility complex class I-related protein 1 (MR1)-restricted, major histocompatibility complex (MHC)-independent recognition, suggesting a potentially reduced risk of alloreactivity. Our previous work showed that higher graft MAIT-cell levels were associated with improved post-transplant MAIT-cell reconstitution and a lower incidence of GI aGVHD. Single-cell ribonucleic acid (RNA) sequencing (sc-RNA-seq) and murine models revealed their functional heterogeneity in immune regulation, tissue repair and chemotaxis-supporting their role as both biomarkers and therapeutic targets. In this prospective study, spectral flow cytometry was used to characterize MAIT-cell phenotypes in peripheral blood stem cell grafts. higher graft MAIT-cell abundance was associated with more robust early post-transplant MAIT-cell reconstitution and a lower risk of GI aGVHD. A three-marker predictive panel based on MAIT-cell functional markers (C-C chemokine receptor type 2 [CCR2], interleukin-4 [IL-4], interleukin-17A [IL-17A]) achieved an area under the receiver operating characteristic curve (AUC) of 0.80, increasing to 0.85 after adjustment for clinical covariates. These findings identify graft-derived MAIT cells as a predictive immune-associated biomarker for GI aGVHD, enabling pre-transplant risk stratification and supporting precision prevention strategies. Trial registration: ChiCTR2500095349.

KMT2A partial tandem duplication (KMT2A-PTD) is a recurrent genetic alteration in acute myeloid leukemia (AML), but its role as a measurable residual disease (MRD) marker before allogeneic hematopoietic stem cell transplantation (allo-HSCT) remains unclear. We retrospectively analyzed 180 KMT2A-PTD AML patients undergoing allo-HSCT at Peking University People's Hospital between 2015 and 2025. Pre-transplant KMT2A-PTD MRD was quantified by real-time quantitative PCR, with positivity defined as ≥1500 copies/10⁵ ABL1. Among 158 patients transplanted in complete remission (CR), 144 had pre-transplant MRD assessment, and 34 (24%) were MRDpositive. Compared with MRD-negative patients, MRD-positive patients had significantly inferior 3- year overall survival (OS, 49% vs. 80%; p.

ABSTRACT Background ASXL1 mutation acute myeloid leukemia represents a clinically aggressive subtype with heterogeneous outcomes. Current evidence remains inconclusive regarding the prognostic relevance of the KRAS mutation partner in AML with ASXL1 mutation. The comprehensive mutational landscape and prognostic implications of co‐occurring driver mutations remain poorly characterized. Methods A total of 2788 consecutive AML patient records were reviewed. A comprehensive clinicogenomic analysis was conducted on 451 AML patients with ASXL1 or KRAS mutations from the discovery cohort (n = 394) and the independent validation cohort (n = 57) to assess the correlation between molecular profiles and clinical outcomes. Results The KRAS mutation was observed in 22 (9.9%) AML cases with the ASXL1 mutation. Notably, survival analysis revealed that the ASXL1mut/KRASmut subtype demonstrated trends toward inferior overall survival (OS) and relapse‐free survival (RFS) relative to ASXL1 single subgroups. Stratified by mutational status, patients with ASXL1mut/KRASmut exhibited significantly inferior 2‐year OS rates (30.5% vs. 59.1% vs. 73.9%; p < 0.001) and short 2‐year RFS (32.7% vs. 59.4% vs. 69.5%; p = 0.002) compared to ASXL1mut/KRASwt or ASXL1wt/KRASmut mutation counterparts. This association persisted in the BeatAML invalidation (OS: 0% vs. 43.1% vs. 69.3%; p = 0.026). This association persisted in the PSM analysis. This co‐mutation confers an exceptionally poor prognosis comparable to that of TP53 mutations or complex karyotypes. HSCT showed no significant survival benefit after landmark analysis (OS; p = 0.292). Conclusions These results demonstrate the independent prognostic value of ASXL1mut/KRASmut co‐mutation and define a novel ultra‐adverse‐risk subtype of acute myeloid leukemia.

Background: The International Consensus Classification (ICC) currently proposes an empirical variant allele frequency (VAF) threshold of 10% to define TP53-mutated acute myeloid leukemia (AML) and to distinguish oncogenic driver from concomitant mutations. However, the optimal cutoff remains uncertain, and the biological and clinical features of low-VAF cases have not been systematically characterized. Methods: In this single-center retrospective cohort study, we stratified TP53-mutated AML by a 10% VAF cutoff and compared clinical characteristics, cytogenetic and molecular profiles, and survival outcomes between groups. Results: The VAF < 10% group exhibited a distinctive profile: fewer adverse cytogenetic abnormalities [complex karyotype, -7, -5/del(5q)], a more adverse molecular profile (EVI1 overexpression, greater co-mutation burden, higher frequencies of ASXL1 and SRSF2 mutations), and a higher proportion of CD34+CD38- blast immunophenotype. TP53 hotspot mutations were also more common. Survival analyses showed poor prognosis in both groups, and the VAF < 10% group showed numerically longer survival without statistical significance, indicating no clear survival advantage for low VAF. Conclusions: These data support the clinical relevance of the ICC 10% threshold. TP53-mutated AML with VAF < 10% may represent a biologically distinct subgroup. Further multicenter studies with larger cohorts are needed to validate and refine the VAF threshold for prognostic evaluation and individualized management.

BACKGROUND:Partial tandem duplication of KMT2A (KMT2A-PTD) is observed not only in acute myeloid leukemia (AML) but also in myelodysplastic syndrome (MDS), while the prognostic value of KMT2A-PTD in MDS needs to be clarified and the optimal therapies for these patients remains unclear. METHODS:In this study, we analyzed 137 MDS patients with KMT2A-PTD from our hospital (PKUPH cohort) and incorporated 2493 MDS patients from the International Working Group for Prognosis in MDS (IWG-PM) cohort, among whom 65 patients had KMT2A-PTD. RESULTS:MDS patients with KMT2A-PTD in IWG-PM cohort had significantly higher blast percentage and IPSS-R score than those without KMT2A-PTD. The 3-year cumulative incidence of leukemia transformation in MDS patients with KMT2A-PTD from both PKUPH and IWG-PM cohort was significantly higher than that in MDS patients without KMT2A-PTD (49.8% [95% CI, 38.6%-61.1%] vs. 19.3% [95% CI, 17.5%-21.2%], P < .001; 58.3% [95% CI, 43.1%-73.5%] vs. 19.3% [95% CI, 17.5%-21.2%], P < .001), respectively. Multivariate analysis in the IWG-PM cohort showed that KMT2A-PTD was an independent poor predictor for leukemia transformation (P < .001). None of co-occurring gene mutations significantly influenced the risk of leukemia transformation in MDS patients with KMT2A-PTD. A landmark analysis in PKUPH cohort suggested that allogenic hematopoietic stem cell transplantation (allo-HSCT) significantly reduced the cumulative incidence of leukemia transformation (P < .001) and the cumulative incidence of relapse (17.6% [95% CI, 5.1%-28.7%] vs. 100% [95% CI, 51.0%-100%], P < .001), respectively. CONCLUSION:KMT2A-PTD may identify a distinct MDS subgroup characterized by a high risk of leukemia transformation, and allo-HSCT could improve outcomes of MDS patients with KMT2A-PTD.

Human parvovirus B19 (B19V) infection is a significant but underrecognized complication, commonly linked not only to aplastic anemia but also pancytopenia, especially in hematopoietic stem cell transplantation (HSCT) recipients. While B19V’s tropism for erythroid progenitor cells (EPCs) is well-documented, its restriction to EPCs fails to fully explain the pathogenesis of pancytopenia. In this study, we used PrimeFlow RNA assay, and single-cell full-length transcriptome sequencing (scFAST-seq) to show that B19V could infect hematopoietic stem cells (HSCs) and initiate viral transcription, resulting in increased apoptosis, impaired self-renewal and multilineage differentiation of HSCs, which may contribute directly to pancytopenia. Further analysis revealed that B19V could activate the JAK2/STAT5 signaling pathway in HSCs to promote viral persistence. Pharmacological inhibition with baricitinib markedly reduced the viral load and partially restored hematopoietic differentiation capacity in vitro. Taken together, our findings reveal B19V as a previously unrecognized HSC-tropic virus that disrupts function of HSCs and may drive pancytopenia. Targeting the JAK2/STAT5 signaling by baricitinib shows promising therapeutic potential for reversing virus-induced bone marrow failure. This work not only deepens our understanding of viral tropism and pathogenesis in the hematopoietic niche, but also opens up new possibilities for treating bone marrow damage after transplantation and in other hematological diseases.

Objectives: To investigate the prognostic value of CEBPA (CCAAT/enhancer-binding protein α) molecular features, such as variant allele frequency (VAF), in patients with de novo acute myeloid leukemia (AML). Methods: Next-generation sequencing (NGS) was used to detect CEBPA mutations in 162 patients with newly diagnosed AML (except acute promyelocytic leukemia). Results: We established 44.2% as the optimal threshold for both maximum VAF and bZIP-domain VAF. The high-VAF group showed higher leukemia burden and inferior event-free survival (EFS). bZIP-domain VAF demonstrated superior prognostic value over maximum VAF (HR: 3.174 vs. 2.460) and was validated across subgroups, namely cytogenetically normal acute myeloid leukemia (CN-AML), chemotherapy-only, and low/intermediate-risk subgroups. Multivariate analysis confirmed high bZIP-domain VAF and DNMT3A mutation as independent risk factors. Conclusions: Our results confirm that the bZIP-domain VAF of CEBPA mutations is a more effective predictor of relapse than the maximum VAF, offering a valuable tool for the early identification of patients at high risk of relapse.

This retrospective study evaluated the efficacy of desensitization therapy using sirolimus and an anti-CD20 monoclonal antibody (n = 47) plus either plasmapheresis (n = 3) or bortezomib (n = 3) in 53 candidates for haploidentical stem cell transplantation (Haplo-SCT) who had pre-transplant donor-specific anti-HLA antibodies (DSA; mean fluorescence intensity [MFI] ≥ 2000). The patients, with a median age of 46 yr (range, 20 to 70), received desensitization therapy within 40 d before transplantation. The median DSA MFI decreased from 9242 (range, 2156 to 20,150) before treatment to 3974 (range, 0 to 16,336) after treatment, 43.4% of the patients became DSA-negative (MFI ≤ 2000), and 62.3% of patients achieved a response, defined as a ≥50% reduction in DSA MFI. Among 31 out of 53 patients who underwent transplantation after receiving myeloablative (n = 19) or reduced-intensity conditioning (n = 12) with infusion of haploidentical allografts and umbilical cord blood, all achieved engraftment without primary graft failure or poor graft function. The 100-d cumulative incidence of acute graft-versus-host disease (GVHD) was 25.8% (95% confidence interval [CI], 10.3% to 41.3%). With a median follow-up of 27 months (range, 3-44), the 1-yr cumulative incidence of chronic GVHD was 31.0% (95% CI, 14.1% to 47.9%). The 1-yr cumulative incidences of relapse and non-relapse mortality were 3.2% (95% CI, 0% to 9.6%) and 10.4% (95% CI, 6.5% to 14.3%), respectively. The 1-yr probabilities of disease-free survival and overall survival were 86.4% and 89.7% (95% CI, 78.5% to 100%), respectively. These findings suggest that sirolimus combined with an anti-CD20 monoclonal antibody based regimen is an effective desensitization strategy that may improve outcomes in DSA-positive Haplo-SCT recipients.

Our previous clinical studies show that all-trans retinoic acid (ATRA) induces a sustained response in patients with immune thrombocytopenia (ITP). However, its mechanisms of action remain unclear. In this study, we observed disorganized cytoskeleton and impaired proplatelet formation (PPF) in megakaryocytes from patients with ITP. Metabolite profiling revealed reduced sphingosine 1-phosphate (S1P) levels in ITP. Decreased sphingosine kinase 2 (SPHK2) expression was responsible for the low S1P levels in ITP. In addition, S1P was essential for activating S1P receptor 1 and Rac1, which regulate cytoskeletal reorganization and PPF. Furthermore, hypoxia-inducible factor-1α (HIF-1α) was shown to mediate SPHK2 and S1P production. Decreased HIF-1α expression in megakaryocytes from patients with ITP contributed to impaired PPF. We subsequently found that ATRA up-regulated HIF-1α and corrected impaired PPF in vitro and in vivo. These findings reveal that ATRA targets the HIF-1α/SPHK2/S1P pathway to improve PPF dysfunction, offering mechanistic insights into its clinical efficacy in ITP.

Acute leukemia (AL), which includes acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL), is a hematological malignancy characterized by the uncontrolled proliferation of immature myeloid or lymphoid cells. Allogeneic stem cell transplantation (ASCT) remains a therapeutic option for patients with AL. Determination of transplantation indications is a key step in successful ASCT and in curing patients. Currently, the measurable residual disease (MRD) is used as a biomarker for response evaluation, relapse prediction, preemptive therapy, and post-remission treatment selection. In this review, we discuss the advantages and disadvantages of these techniques for MRD detection. We focused mainly on the residual disease-directed selection of transplant indications for patients with either AML or ALL and provided expert opinions in these settings. We also discuss the challenges associated with transplantation indications and propose expert opinions and future directions for the selection of indications for transplantation.

Rapid, quantitative analysis of single-cell proteins with arbitrary spatial distributions carries pivotal significance across fundamental biological research and clinical applications. However, as the golden method, flow cytometry can only quantify cell surface proteins due to non-uniform excitation illumination and the lack of calibration microbeads with known numbers of internal fluorescent molecules. This study reported a quantitative microfluidic flow cytometer utilizing aligned microfabricated metal apertures to selectively extract the central portions of Gaussian beams, forming a spaced uniform optical field. Based on this spaced uniform optical field, multicolor fluorescence signals originating from antibody-binding events with arbitrary distributions on single microbeads were converted into the number of proteins. The geometries of the microfluidic cuvette and the uniformity of fluorescence intensities across the excitation fields were quantitatively validated. Using this methodology, calibration curves with high linearities for all nine fluorescence channels were established, and a mixture of rainbow calibration microbeads was analyzed, where five types of fluorescent probes were quantitatively measured, enabling the classification of the rainbow mixture into five distinct subpopulations. The presented flow cytometer enables quantitative analysis of single-cell proteins with arbitrary spatial distributions and thus demonstrates strong potential for fundamental biological research and clinical applications at the single-cell level.

Viral enteritis is a common complication after allogeneic hematopoietic stem cell transplantation (allo-HSCT). However, data regarding the most frequent enteric pathogens, clinical characteristics, and patient outcomes remains limited. To better characterize post-HSCT viral enteritis, we retrospectively analyzed 59 patients who underwent allo-HSCT and were diagnosised with viral enteritis based on intestinal biopsy specimens. The most frequently identified pathogens were cytomegalovirus (CMV), human herpesvirus 6 (HHV-6), and Epstein-Barr virus (EBV), accounting for 37.3%, 37.3%, and 33.9% of cases, respectively. The median time for diagnosis was 56 days post-allo-HSCT. Diarrhea and abdominal pain were the predominant symptoms. Notably, 35 patients experienced diarrhea lasting 14 days or more, with a median duration of 16 days (range: 3-57 days). Forty-five patients were diagnosed with concurrent graft-versus-host disease (GVHD) by endoscopic examination. The overall survival rates for patients with viral enteritis at 1 and 3 years were 68.7% and 58.1%, respectively. Importantly, patients with CMV enteritis had significantly poorer overall survival compared to those with other viral enteritis types (P = 0.035). In conclusion, viral enteritis is a significant complication following allo-HSCT, with CMV, HHV-6, and EBV being the most common pathogens. Early identification and management are crucial, especially for CMV enteritis which is associated with poorer outcomes.

BACKGROUND:Severe pneumonia after allogeneic hematopoietic stem cell transplantation (allo-HSCT) is associated with high mortality. Given that cytokines, including interleukin 6 (IL-6), play a critical role in immune-mediated organ injury in patients with severe coronavirus disease 2019 (COVID-19), we hypothesized that cytokines may also contribute to the pathogenesis of severe pneumonia after allo-HSCT. This study aimed to investigate the role of IL-6 in severe pneumonia after allo-HSCT and explore its underlying mechanism. METHODS:Serum cytokine levels were prospectively measured in patients with severe and nonsevere pneumonia following allo-HSCT. A mouse model of acute lung injury (ALI) and in vitro experiments using primary murine pulmonary microvascular endothelial cells (PMVECs) were conducted to assess the effects of IL-6 blockade, the mechanism of IL-6 in ALI, and immune-induced ALI. RESULTS:Serum IL-6 and soluble IL-6 receptor (sIL-6R) levels were higher in the severe pneumonia group than in the nonsevere group and were associated with disease progression. In a mouse model, preventive IL-6 blockade reduced ALI and improved survival. In vitro, the IL-6 trans-signaling complex caused more severe damage to mouse PMVECs than the classical signaling pathway. Soluble glycoprotein 130 and ruxolitinib effectively blocked the JAK1/STAT3 pathway activated by IL-6 trans-signaling in mouse PMVECs and reduced downstream inflammatory responses. CONCLUSIONS:IL-6 levels were elevated in patients with severe pneumonia after allo-HSCT and were linked to disease progression. This injury may be driven by the IL-6/sIL-6R/JAK1/STAT3 pathway. This preliminary study suggests that targeting the IL-6 trans-signaling pathway may be a promising therapeutic approach for severe pneumonia/ALI following allo-HSCT.