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X-linked sideroblastic anemia (XLSA) in carrier females of ALAS2 mutations is not uncommon. We describe unique features and genotype/phenotype correlations in XLSA females and evaluate the contributions of X-chromosome skewing and clonal hematopoiesis, emphasizing the importance of distinguishing it from myelodysplastic syndromes with ring sideroblasts.

Extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (EMZL) invariably develops from a background of chronic inflammatory disorder caused by a diverse chronic microbial infection and/or autoimmunity depending on the site. These chronic inflammatory/autoimmunity disorders trigger innate and acquired immune responses, generating a unique microenvironment at each site which drives clonal evolution of B cells, their expansion and eventual malignant transformation. At a molecular level, this involves temporal and spatial acquisition of cooperative oncogenic events by dysregulated immune responses and somatic genetic changes. Although these events are not yet fully characterised, EMZL at several sites shows distinct genetic profiles and molecular insights, bridging the pathological process to lymphomagenesis. For example, gastric EMZL, particularly those lacking a BCL10 or MALT1 translocation, critically depend on T-helper cell signals produced by immune responses to Helicobacter pylori infection. Likewise, thyroid EMZL may also involve exaggerated T-cell help due to highly frequent inactivating mutations in TET2, CD274 (PD-L1) and TNFRSF14, which impede the co-inhibitory interactions between the neoplastic B and T-helper cells, thus releasing T-cell help. Ocular adnexal EMZL shows frequent TNFAIP3 (A20) mutation/deletion that significantly associates with expression of autoreactive IGHV4-34 BCR, emphasising their potential cooperation in NF-kB pathway activation. Finally, the genesis of salivary gland EMZL may be closely associated with GPR34 activation that is caused by mutation/t(X;14)(p11;q32) and/or paracrine stimulation mediated by ligand generated by lymphoepithelial lesions. This review will focus on these novel molecular insights and how these advances may provide a paradigm for future investigations.

Controlled development of cellular intestinal immunity in the face of dynamic microbiota emergence constitutes a major challenge in very early life, and a bottleneck for sustained growth and well-being. Early-onset inflammatory bowel disease (IBD) represents an extreme disturbance of intestinal immunity. It is a hallmark, and often the first manifestation of chronic granulomatous disease (CGD), caused by inborn defects in the NADPH oxidase NOX2 and thus the failure to produce reactive oxygen species (ROS) in phagocytes. However, in contrast to the known role of ROS in antimicrobial defense, the mechanisms underlying intestinal immunopathology in CGD remain enigmatic. This is partly due to the incomplete recapitulation of the CGD-IBD phenotype in established mouse models. We found that mice deficient in the NOX2 subunits p47phox or gp91phox showed similar baseline disturbances in lamina-propria macrophage differentiation, but they responded differently to chemically-induced colitis. Although p47phox and gp91phox-deficient mice differed markedly in microbiota composition, cross-fostering failed to equalize discrepant IBD phenotypes and microbiota, pointing at extremely early and functionally important microbiota fixation under specific pathogen-free housing conditions. In contrast, neonatal acquisition of a complex wild-mouse-microbiota triggered spontaneous IBD, granuloma formation and secondary sepsis with intestinal pathogens in both NOX2-deficient mouse lines, which was in part dependent on NOX2 in intestinal macrophages. Thus, in experimental CGD, the aberrant development of tissue immunity and the microbiota are closely intertwined immediately after birth.

The incidence of venous thromboembolism in children continues to rise, with the most recent analysis from the Pediatric Hospital Information Systems database in the United States reporting a 200-fold increase in pediatric hospitalization-related venous thromboembolism diagnoses over the past two decades. In the past decade, several pediatric venous thromboembolism risk prediction models have been published, in some cases derived from multi-institutional data and multicenter randomized clinical trials of thromboembolism prevention in specific pediatric subpopulations have been conducted. Yet, apart from children hospitalized for COVID-19, guidelines for thromboprophylaxis (TP) in children that address several distinct at-risk subpopulations and settings for venous thromboembolism are presently lacking. It is becoming increasingly apparent that approaches to pharmacological TP for hospitalized children should be risk-stratified regarding a priori risks of both venous thromboembolism and clinically-relevant bleeding. In this manuscript, we present model cases of common inpatient clinical scenarios and review the evidence related to venous thromboembolism risk models and pharmacological TP clinical trials in children, describing a pragmatic approach to pharmacological TP for each scenario. We then conclude by describing our evidence-informed, subpopulation- and setting-specific approach to pharmacological TP for the clinical scenarios and reviewing critical knowledge gaps well-suited for future pediatric trials to inform thromboprophylaxis in children.

Chronic graft-versus-host disease (cGVHD) is the leading cause of morbidity and non-relapse associated mortality following allogeneic hematopoietic cell transplantation (aHSCT). Treating steroid resistant/refractory cGVHD remains challenging. Epigenetic regulators can have global transcriptional effects that control donor T-cell responses. We previously showed that inhibiting histone lysine motifs by chromatin-modifying enzymes can ameliorate murine cGVHD. Targeting donor T-cell DNA methyltransferases reduce acute GVHD. Here, we sought to investigate the DNA demethylase Tet (ten-eleven translocase) methylcytosine dioxygenases 2 (Tet2) and Tet3 in T follicular helper cell (TFH) dependent cGVHD. In a clinically relevant model of cGVHD that recapitulates pulmonary fibrosis from bronchiolitis obliterans, recipients of Tet2 deleted donor T-cells did not have improved pulmonary function tests in contrast to the markedly improved pulmonary function in Tet3 deleted donor T-cells. Tet3 deleted donor T-cells did not impair TFH-dependent germinal center (GC) formation. Unexpectedly, TET3 deficiency resulted in elevated GATA3 expression in and IL-4 production by TFH cells. TET3 deficient TFH cells supported GC B-cell immunoglobulin (Ig) class switching to nonpathogenic IgG1 but not pathogenic IgG2c allowing mice to escape cGVHD pulmonary fibrosis. Elevated GATA3 expression and disruption of IgG2c class switching was recapitulated in an in-vitro human GC culture system. These studies provide new insights into the function of Tet3 in TFH driven Ig class switching and suggest a new approach to mitigate cGVHD.

The contribution of IL-10 secreted by tumoral B cells to the progression and shaping of the microenvironment in diffuse large B-cell lymphoma (DLBCL) with activated B-cell (ABC) phenotype is not yet completely understood. To shed light on this issue, we generated an immunocompetent mouse model of ABC-DLBCL with conditional knock-out of IL-10 specifically in malignant B cells. Paradoxically, these mice had significantly worse overall survival when left untreated, but experienced increased sensitivity to conventional anti-CD20 immunotherapy or regulatory T cell (Treg) depletion. We identified various immunomodulatory mechanisms involved in this behavior. In particular, we show that IL-10-deficient lymphomas acquire a highly immunosuppressed and T-cell exhausted microenvironment with increased angiogenesis that results in a more aggressive phenotype, refractory to PD-1 immune checkpoint blockade (ICB). However, the response of IL-10-deficient mice to anti-CD20 immunotherapy was greatly enhanced by upregulation of calcium channels in B cells. In general, IL-10 autocrine signaling promotes survival of malignant B cells, while the paracrine action of B cell-derived IL-10 maintains an immunoreactive microenvironment that influences the efficacy of emerging immunotherapy strategies aimed at the lymphoma microenvironment (LME). Furthermore, IL-10-associated transcriptional signatures derived from our studies may correctly predict clinical outcomes of DLBCL patients treated with R-CHOP. Thus, our work provides important functional and mechanistic insights into the role of B cell-derived IL-10 in the biology of ABC-DLBCL.

Abstract: Sterile alpha motif domain-containing protein 9 (SAMD9) and SAMD9-like (SAMD9L) are paralogous genes encoding antiviral proteins that negatively regulate cell proliferation. Heterozygous germ line gain-of-function (GoF) SAMD9/9L variants cause multisystem syndromes with variable manifestations. The unifying features are cytopenia, immunodeficiency, infections, bone marrow failure, myelodysplasia, and monosomy 7. Nonhematopoietic presentations can affect almost every organ system. Growth impairment and adrenal insufficiency are typical in SAMD9, whereas progressive neurologic deficits characterize SAMD9L. Most patients (>90%) carry germ line missense GoF variants. A subgroup of patients presenting with SAMD9L-associated inflammatory disease carry frameshift-truncating variants that are also GoF. Somatic genetic rescue occurs in two-third of patients or more and involves monosomy 7, which may spontaneously disappear (transient monosomy 7) or progress to myelodysplastic syndrome (MDS)/leukemia, and adaptive clones with somatic SAMD9/9L compensatory mutations or uniparental disomy 7q (UPD7q), both associated with remission. This manuscript examines the clinical and genetic spectrum, therapies, and outcome based on 243 published patients compiled in our registry, with additional genetic information on 62 unpublished cases. We consolidate the diverse clinical manifestations and diagnostic challenges of SAMD9/9L syndromes to enhance recognition and improve patient care. We highlight the knowledge gaps in pathomechanisms and emphasize the importance of genetic surveillance assessing disease remission vs disease progression. Insights are provided into variant curation and the necessity of testing for somatic SAMD9/9L mutations and UPD7q. Multidisciplinary care in specialized centers is critical to manage these complex disorders. Future natural history studies, especially in patients with monosomy 7, will help formulate evidence-based surveillance protocols and optimize transplant timing and outcomes.

Abstract: CD47 is overexpressed on the surface of many types of cancer cells, including T-cell acute lymphoblastic leukemia (T-ALL) cells. In this study, we have developed a diphtheria toxin (DT)-based bivalent anti-human CD47 immunotoxin (bi-CD47-IT) for the targeted therapy of CD47+ cancers using a unique DT-resistant yeast Pichia pastoris expression system. Bi-CD47-IT demonstrated compelling in vivo efficacy in multiple T-ALL cell line-derived xenograft (CDX) and patient-derived xenograft (PDX) mouse models. Bi-CD47-IT significantly prolonged the median survival of the tumor-bearing mice and highly effectively depleted the T-ALL blast cells in the peripheral blood, spleen, liver, bone marrow, brain, and spinal cord in the T-ALL CDX and PDX mouse models. Bi-CD47-IT cured 60% of tumor-bearing mice in a T-ALL Molt-4 CDX mouse model. Because CD47 is also expressed on normal tissues, including red blood cells and lymphocytes, specificity is a concern. We thus analyzed the in vitro binding avidity and hemagglutination of bi-CD47-IT in human red blood cells, finding no binding or hemagglutination. We further performed a toxicity study of bi-CD47-IT in humanized mice, which showed that bi-CD47-IT transiently depleted the human lymphocytes for ∼4 weeks after the 10-day treatment. No clinical adverse events were observed. As a result, bi-CD47-IT appears to possess the "optimal" binding avidity, with effective binding to human CD47+ T-ALL tumor cells, no binding to human red blood cells, and weak binding to human lymphocytes. We believe that bi-CD47-IT is a promising and safe therapeutic drug candidate for the targeted therapy of CD47+ cancers.