Noncoding mutations drive persistence of a founder preleukemic clone which initiates late relapse in T-ALL.

ABSTRACT: T-ALL relapse usually occurs early but can occur much later, which has been suggested to represent a de novo leukemia. However, we conclusively demonstrate late relapse can evolve from a pre-leukemic subclone harbouring a non-coding mutation that evades initial chemotherapy.

Effects of TNF-α inhibition versus secukinumab on active ultrasound-confirmed enthesitis in psoriatic arthritis.

Introduction: Enthesitis is a hallmark of psoriatic disease, but its clinical assessment is problematic in terms of diagnostic sensitivity and overlap with other comorbid conditions. Ultrasound is a useful tool that can give a more detailed assessment of enthesitis. Research demonstrates that those with persistent ultrasound entheseal disease are at risk of progressive articular damage. With limited data to guide choice between biologic therapy for psoriatic arthritis (PsA) patients, we wanted to assess the response of ultrasound-confirmed enthesitis to different forms of biologic therapies and study its utility in making more informed decisions. Methods: This was an open label observational study including patients aged ⩾18 years, who fulfil the classification criteria for PSA (CASPAR) and were due to commence on their first biologic therapy. The primary outcome was the change in MAdrid Sonographic Enthesitis Index (MASEI) score at 16 weeks of treatment. The MASEI score was also modified to assess the active elementary lesions (ActiveMASEI). Results: In all, 80 PsA patients were enrolled with 75 patients completing the study [secukinumab n = 23 and tumour necrosis factor inhibitor (TNFi) n = 52]. The mean reduction in MASEI score after 16 weeks of treatment was 3.42 with TNFi versus 1.74 with secukinumab (p = 0.097). There was a significant difference in the change in the MASEIActive score for TNFi versus secukinumab (4.37 versus 2.26; p = 0.030) and this difference was more pronounced when only power Doppler signal within 2 mm of the enthesis insertion was included (4.37 versus 2.00; p = 0.007). Clinical outcomes were similar for both classes of biologic apart from a significant reduction in regards to the Dermatology Life Quality Index and Psoriasis Area and Severity Index score with secukinumab versus TNFi. Conclusions: We have for the first time compared the effect of ultrasound-confirmed enthesitis between different forms of biologic therapies for PsA. We have seen an overall improvement in entheseal scores for both classes of medications and demonstrated a larger reduction in active entheseal disease for TNFi versus secukinumab that merits further exploration.

Introduction: An enthesis is the point at which ligament and tendon insert into the bone and enthesitis is the inflammation at these sites causing pain and reduced function.Enthesitis is particularly common in patients with psoriatic arthritis and it has been shown to be important in the development, diagnosis and prognosis of the condition. Clinical examination has limitations and imaging techniques like ultrasound have been proven to give a more detailed assessment of enthesitis potentially revealing clues to the condition itself. In psoriatic arthritis, we do not have a good way of choosing between biologic therapies that can treat inflammation. With a better understanding of enthesitis and its response to various therapies, we may be able to make better decisions. We wanted to examine the extent of enthesitis within a group of psoriatic arthritis patients who were to commence on their first biologic therapy by examining them both with ultrasound and then with clinical examination. Methods: We recruited 80 patients in which their consultant rheumatologist had decided to commence them on therapy. We carried out an ultrasound assessment of six entheseal sites as per an established assessment tool called the MAdrid Sonographic Enthesitis Index (MASEI). We then proceeded to take a history from the patients and examine all aspects of their joint disease just before they began their therapy. We repeated the ultrasound and clinical examination after 16 weeks of treatment without knowing what treatment they were on. Results: In all, 75 patients completed the study and 23 of these were treated with secukinumab, a drug that targets interleukin-17a (IL-17i), an important protein in psoriatic disease and 52 patients were treated with medications that target tumour necrosis factor inhibitor (TNFi), another important inflammatory protein. Overall, we demonstrated a reduction in ultrasound scores for entheseal disease in those treated with both classes of medication. For the TNFi group, there was a larger improvement in scores compared with the IL-17i which was not significant for the primary focus of the study, the overall MASEI score. We have also demonstrated that there may be a larger improvement in TNFi response versus IL-17i when only counting the inflammatory disease component of the MASEI score. In terms of clinical results, the findings were broadly similar except that secukinumab was better at improving skin psoriasis. Conclusion: Our work is the first with ultrasound to compare outcomes for enthesitis between classes of biologic therapy and should form the basis of future studies attempting to confirm these findings to make better decisions for those living with psoriatic arthritis.

Food Security Status, WIC Participation, and Early Childhood Caries in a Nationally Representative Sample of Children.

BACKGROUND: Despite the potential role of the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) in mitigating the adverse effects of food insecurity on oral health, to our knowledge, no study has examined whether WIC participation could modify the association between food insecurity with caries in young children. OBJECTIVE: Our aim was to investigate the impact of WIC participation in modifying the association between food insecurity and early childhood caries. DESIGN: This was a cross-sectional study. PARTICIPANTS/SETTING: Using 2011-2018 National Health and Nutrition Examination Survey data, children aged 2 through 5 years; with household income ≤185% of the Federal Poverty Level; and with data on WIC participation, food security, and dental examinations were included (n = 1,921). STUDY EXPOSURES: Food-security status and WIC participation were the study exposures. MAIN OUTCOME MEASURES: Total and untreated dental caries were the main outcome measures. STATISTICAL ANALYSES: Logistic regression examined associations of food security (household-level and child-level) and WIC participation with odds of caries. Interactions between food security and WIC participation were examined using multiplicative interaction terms. RESULTS: Marginal child food security was significantly related to higher odds of total caries in income-eligible WIC nonparticipants (odds ratio 1.92; 95% CI 1.07 to 3.46); however, this relationship was not observed in WIC participants. Furthermore, food insecurity was significantly associated with greater odds of untreated caries only among income-eligible WIC nonparticipants (odds ratio 1.79; 95% CI 1.12 to 2.85). CONCLUSIONS: In this sample of preschool-aged children, the relationship of food insecurity with caries differed by WIC participation status. Findings suggest that WIC participation could improve the oral health of income-eligible children with lower levels of food security.

CD169+ Monocyte and Regulatory T Cell Subsets Are Associated with Disease Activity in Rheumatoid Arthritis.

Disease activity in rheumatoid arthritis (RA) is influenced by activation of circulating and synovial immune cells. Regulatory T cells (Tregs) and monocytes are key cells that drive inflammation in RA. This study investigated if a relationship exists between disease activity in RA and circulating Treg and monocyte numbers and phenotypes. A potential sialic acid (Sia) mediated link between Tregs and monocytes was also probed in vitro. Peripheral blood mononuclear cells (PBMCs) were isolated from RA patient (n = 62) and healthy control (n = 21) blood using density gradient separation. Flow cytometry was used to count and phenotype Treg and monocyte subsets, and to sort healthy control Tregs for Sia cell culture experiments. The effects of Sia on activated Treg FoxP3 and NFκB expression was assessed by flow cytometry and concentrations of secreted TNFα, IL-10 and IFNγ determined by ELISA. High disease activity RA patients who were unresponsive to disease modifying anti-rheumatic drugs (n = 31), have significantly lower relative numbers (percentages) of CD4+CD25+CD127− Tregs (p < 0.01) and memory CD45RA−FoxP3+ Tregs (p < 0.01), compared to low disease activity responders (n = 24). Relative numbers of non-classical CD169+ monocytes are associated with disease activity in RA (p = 0.012). Sia reduced Treg expression of FoxP3, NFκB and cytokines in vitro. A strong association has been identified between non-classical CD169+ monocytes and post-treatment disease activity in RA. This study also indicates that Sia can reduce Treg activation and cytokine release. We postulate that such a reduction could be mediated by interaction with sialyted proteins captured by CD169+ monocytes.

Association between systemic sclerosis, palmar fasciitis with polyarthritis, Raynaud's phenomenon and erythromelalgia with underlying malignancy.

The symptoms of a rheumatic disease may also be a sign of a proliferative process. These include conditions that present with skin and vascular changes such as systemic sclerosis and Raynaud's phenomenon with peripheral ischaemia and ulceration. Furthermore, the less common conditions - erythromelalgia or palmar fasciitis with polyarthritis may also accompany cancer. In this article, we discuss the association of diffuse systemic sclerosis with anorectal tumor, palmar fasciitis and polyarthritis with ovarian cancer, erythromelalgia with underlying ovarian malignancy and Raynaud's phenomenon and digital ischemia associated with renal carcinoma. Based on the literature review on this topic we highlighted the importance of recognizing paraneoplastic syndromes at an early stage. This is a crucial point in the adequate management of a patient. Many of the paraneoplastic symptoms of rheumatic and other described conditions may regress with the management of the underlying malignancy.

UK Expert Consensus Statement for the Optimal Use and Clinical Utility of Leadless Pacing Systems on Behalf of the British Heart Rhythm Society.

Pacemakers are a key technology in the treatment of bradyarrhythmias. Leadless pacemakers (LP) were introduced to address limitations of transvenous devices. However, guidelines and other restrictions have led to LPs becoming niche products. The aim of this consensus statement was to determine the strength of opinion of UK implantation experts as to how LPs can be more optimally used. Using a modified Delphi approach, a panel of LP experts developed 36 statements that were used to form a survey that was distributed to LP implanters in the UK. Stopping criteria included a 3-month window for response, a minimum 25% response rate and at least 75% of statements achieving the threshold for consensus (agreed at 66%). In all, 31 of 36 statements reached consensus, and 23 of these achieved ≥90% agreement. Five statements did not achieve consensus. On the basis of these results, seven recommendations were proposed. The implementation of these recommendations may increase the use of LPs, with the aim of improving patient outcomes.

ATRPred: A machine learning based tool for clinical decision making of anti-TNF treatment in rheumatoid arthritis patients.

Rheumatoid arthritis (RA) is a chronic autoimmune condition, characterised by joint pain, damage and disability, which can be addressed in a high proportion of patients by timely use of targeted biologic treatments. However, the patients, non-responsive to the treatments often suffer from refractoriness of the disease, leading to poor quality of life. Additionally, the biologic treatments are expensive. We obtained plasma samples from N = 144 participants with RA, who were about to commence anti-tumour necrosis factor (anti-TNF) therapy. These samples were sent to Olink Proteomics, Uppsala, Sweden, where proximity extension assays of 4 panels, containing 92 proteins each, were performed. A total of n = 89 samples of patients passed the quality control of anti-TNF treatment response data. The preliminary analysis of plasma protein expression values suggested that the RA population could be divided into two distinct molecular sub-groups (endotypes). However, these broad groups did not predict response to anti-TNF treatment, but were significantly different in terms of gender and their disease activity. We then labelled these patients as responders (n = 60) and non-responders (n = 29) based on the change in disease activity score (DAS) after 6 months of anti-TNF treatment and applied machine learning (ML) with a rigorous 5-fold nested cross-validation scheme to filter 17 proteins that were significantly associated with the treatment response. We have developed a ML based classifier ATRPred (anti-TNF treatment response predictor), which can predict anti-TNF treatment response in RA patients with 81% accuracy, 75% sensitivity and 86% specificity. ATRPred may aid clinicians to direct anti-TNF therapy to patients most likely to receive benefit, thus save cost as well as prevent non-responsive patients from refractory consequences. ATRPred is implemented in R.

High-throughput sequencing of peripheral blood for minimal residual disease monitoring in childhood precursor B-cell acute lymphoblastic leukemia: A prospective feasibility study.

BACKGROUND: Minimal residual disease (MRD) measured on end-of-induction bone marrow (BM) is the most important biomarker for guiding therapy in pediatric acute lymphoblastic leukemia (ALL). Due to limited sensitivity of current approaches, peripheral blood (PB) is not a reliable source for identifying patients needing treatment changes. We sought to determine if high-throughput sequencing (HTS) (next-generation sequencing) of rearranged immunoglobulin and T-cell receptor genes can overcome this and be used to measure MRD in PB. PROCEDURE: We employed a quantitative HTS approach to accurately measure MRD from one million cell equivalents of DNA from 17 PB samples collected at day 29 after induction therapy in patients with precursor B-cell ALL. We compared these results to the gold-standard real-time PCR result obtained from their paired BM samples, median follow-up 49 months. RESULTS: With the increased sensitivity, detecting up to one abnormal cell in a million normal cells, we were able to detect MRD in the PB by HTS in all those patients requiring treatment intensification (MRD ≥ 0.005% in BM). CONCLUSION: This is proof of principle that using the increased sensitivity of HTS, PB can be used to measure MRD and stratify children with ALL. The method is cost effective, rapid, accurate, and reproducible, with inherent advantages in children. Importantly, increasing the frequency testing by PB as opposed to intermittent BM sampling may allow extension of the dynamic range of MRD, giving a more complete picture of the kinetics of disease remission while improving relapse prediction and speed of detection.

The relationship between the nail and systemic enthesitis in psoriatic arthritis.

OBJECTIVE: Psoriatic nail disease is more common in PsA than in isolated skin psoriasis (PsO). The nail is closely integrated to the DIP joint entheses. US data have shown that those patients with nail disease in PsO are more likely to have systemic enthesitis. We examined whether there was a relationship between nail disease, DIP enthesitis and systemic enthesitis in established PsA. METHODS: Forty-six PsA participants with nail disease underwent US scanning of the nail unit and the DIP entheses along with peripheral entheseal sites according to the Madrid sonographic enthesitis index (MASEI). RESULTS: At the finger level, there was a mild to moderate correlation between nail US changes and both clinical nail disease and DIP enthesis changes (DIP US) [Spearman correlation (r S) = 0.30, P < 0.001 and r S = 0.16, P < 0.001, respectively]. At the patient level, there was a moderate correlation between the nail US score and nail psoriasis severity index score and DIP US (r S = 0.33, P = 0.024 and r S = 0.43, P = 0.003, respectively). At the patient level, there was also a positive correlation between a higher nail US score and the active peripheral enthesitis score (MASEI-active) (r S = 0.35, P = 0.018). When power Doppler was part of nail US score, similar results were demonstrated at both the finger and patient levels. CONCLUSION: This study has demonstrated the utility of nail US imaging and the close relationship, on scanning, between the DIP entheses and the nail unit. In PsA, we have seen a correlation between active US changes at the nail and peripheral enthesitis, which requires further analysis. TRIAL REGISTRATION: ClinicalTrials.gov, https://clinicaltrials.gov, NCT03955861.

A human fetal liver-derived infant MLL-AF4 acute lymphoblastic leukemia model reveals a distinct fetal gene expression program.

Although 90% of children with acute lymphoblastic leukemia (ALL) are now cured, the prognosis for infant-ALL remains dismal. Infant-ALL is usually caused by a single genetic hit that arises in utero: an MLL/KMT2A gene rearrangement (MLL-r). This is sufficient to induce a uniquely aggressive and treatment-refractory leukemia compared to older children. The reasons for disparate outcomes in patients of different ages with identical driver mutations are unknown. Using the most common MLL-r in infant-ALL, MLL-AF4, as a disease model, we show that fetal-specific gene expression programs are maintained in MLL-AF4 infant-ALL but not in MLL-AF4 childhood-ALL. We use CRISPR-Cas9 gene editing of primary human fetal liver hematopoietic cells to produce a t(4;11)/MLL-AF4 translocation, which replicates the clinical features of infant-ALL and drives infant-ALL-specific and fetal-specific gene expression programs. These data support the hypothesis that fetal-specific gene expression programs cooperate with MLL-AF4 to initiate and maintain the distinct biology of infant-ALL.

Associations Between Diet Quality and Dental Caries in Low-Income Women.

BACKGROUND: The Healthy Eating Index 2015 (HEI-2015) is a diet quality measure of conformity of diet to the 2015-2020 Dietary Guidelines for Americans. This tool is being used increasingly to assess relationships between diet quality and health outcomes. OBJECTIVE: The objective of this research was to investigate the relationships between diet quality as measured by HEI-2015 total and component scores and Decayed, Missing, Filled Teeth Index (DMFT) scores in low-income women. DESIGN: In this cross-sectional study, low-income women were administered questionnaires and dental examinations on 1 occasion. The questionnaires included demographics, food frequency, and oral health questionnaires, and the US Adult Food Security Survey Module. PARTICIPANTS/SETTINGS: Participants in this study were part of a larger research project-Impact of Diet and Nutrition on Dental Caries in Low-Income Women. For the larger research project, a total of 255 women aged 18 to 50 years with annual income <250% of the Federal Poverty Line were recruited from low-income housing units in Central Texas from June 1, 2018 to December 30, 2018. Of the 255 women, 28 underwent dental screenings but did not complete the questionnaires. Seven women were excluded because energy intakes exceeded 4,000 kcal/d. The final sample for the current analysis was 220 women who had completed their dental examinations and provided complete data. MAIN OUTCOME MEASURES: The exposure was diet quality and the main outcome measure was DMFT score. STATISTICAL ANALYSIS: Dental caries scores were calculated by addition of decayed, missing, and filled teeth. Descriptive statistics were conducted on the variables of age, race and ethnicity, education, annual household income, food security status, and frequency of brushing and flossing. Linear regression analysis was used to discern relationships between diet quality-as assessed by HEI-2015 total and component scores-and dental caries experience, adjusting for the covariates. RESULTS: Caries in permanent teeth was present in 95.6% of participants. HEI-2015 total scores were inversely associated with dental caries. An increase of 1 point in total HEI-2015 score was accompanied by a decrease in DMFT score by 0.569 (P = .001). In addition, component scores for total vegetables (P = .001), greens and beans (P = .002), dairy (P = .004), refined grains (P = .001), and added sugars (P = .001) were inversely related to DMFT scores. CONCLUSIONS: This research suggests that diet quality, as measured by the HEI-2015, is inversely associated with DMFT scores in low-income women. Future research is needed to investigate the influence of diet and nutrition on the integrity of oral health.

Anti-tumour necrosis factor-alpha response associated with combined CD226 and HLA-DRB1[*]0404 haplotype in rheumatoid arthritis.

OBJECTIVES: Predicting response to anti-tumour necrosis factor alpha (anti-TNFα) drugs at baseline remains an elusive goal in rheumatoid arthritis (RA) management. The purpose of this study was to determine if baseline genetic variants of PTPRC, AFF3, myD228, CHUK, MTHFR1, MTHFR2, CD226 and a number of KIR and HLA alleles could predict response to anti-TNF-α in rheumatoid arthritis patients. METHODS: Peripheral blood samples were collected from 238 RA patients treated with anti-TNFα drugs. Genotyping was performed using biochip array technology by Randox Laboratories Ltd. and sequence specific polymerase chain reaction. Linear regression analysis was performed to investigate the role of these genotypes in predicting response to treatment, as defined by European League Against Rheumatism (EULAR) response classification and absolute change in disease activity score (DAS28). RESULTS: Of 238 RA patients analysed, 50.4% received adalimumab, 29.7% received etanercept, 14.8% received infliximab, 3.4% certoluzimab and 1.7% golimumab. The MTHFR1 variant rs1801133 was significantly associated with the EULAR response, p=0.044. Patients with the HLA-DRB1*0404 allele displayed a significantly larger reduction in DAS28 compared to non-carriers (mean -2.22, -1.67 respectively, p=0.033). CD226 rs763361 was the only SNP variant significantly associated with ΔDAS28 (p=0.029). CONCLUSIONS: This study has investigated individual allele associations with reductions in DAS28 across a range of anti-TNFα treatments. A combined predictive model indicates that patients with the HLA-DRB1*0404 allele and without the CD226 rs763361 polymorphism exhibit the largest reduction in DAS28 after anti-TNF-α treatment.

Antitumor activity without on-target off-tumor toxicity of GD2-chimeric antigen receptor T cells in patients with neuroblastoma.

The reprogramming of a patient's immune system through genetic modification of the T cell compartment with chimeric antigen receptors (CARs) has led to durable remissions in chemotherapy-refractory B cell cancers. Targeting of solid cancers by CAR-T cells is dependent on their infiltration and expansion within the tumor microenvironment, and thus far, fewer clinical responses have been reported. Here, we report a phase 1 study (NCT02761915) in which we treated 12 children with relapsed/refractory neuroblastoma with escalating doses of second-generation GD2-directed CAR-T cells and increasing intensity of preparative lymphodepletion. Overall, no patients had objective clinical response at the evaluation point +28 days after CAR-T cell infusion using standard radiological response criteria. However, of the six patients receiving ≥108/meter2 CAR-T cells after fludarabine/cyclophosphamide conditioning, two experienced grade 2 to 3 cytokine release syndrome, and three demonstrated regression of soft tissue and bone marrow disease. This clinical activity was achieved without on-target off-tumor toxicity. Targeting neuroblastoma with GD2 CAR-T cells appears to be a valid and safe strategy but requires further modification to promote CAR-T cell longevity.

Correction to: Integrin-FAK signaling rapidly and potently promotes mitochondrial function through STAT3.

An amendment to this paper has been published and can be accessed via the original article.

Exogenous ubiquitin attenuates hypoxia/reoxygenation-induced cardiac myocyte apoptosis via the involvement of CXCR4 and modulation of mitochondrial homeostasis.

Exogenous ubiquitin (UB) plays a protective role in ß-adrenergic receptor-stimulated and ischemia/reperfusion (I/R)-induced myocardial remodeling. Here, we report that UB treatment inhibits hypoxia/reoxygenation (H/R)-induced apoptosis in adult rat ventricular myocytes (ARVMs). The activation of Akt was elevated, whereas the activation of glycogen synthase kinase-3ß was reduced in UB-treated cells post-H/R. The level of oxidative stress was lower, whereas the number of ARVMs with polarized mitochondria was significantly greater in the UB-treated samples. ARVMs express CXCR4 with majority of CXCR4 localized in the membrane fraction. CXCR4 antagonism using AMD3100, and siRNA-mediated knockdown of CXCR4 negated the protective effects of UB. Two mutated UB proteins (unable to bind CXCR4) had no effect on H/R-induced apoptosis, activation of Akt and GSK-3ß, or oxidative stress. UB treatment enhanced mitochondrial biogenesis, and inhibition of mitochondrial fission using mdivi1 inhibited H/R-induced apoptosis. Ex vivo, UB treatment significantly decreased infarct size and improved functional recovery of the heart following global I/R. Activation of caspase-9, a key player of the mitochondrial death pathway, was significantly lower in UB-treated hearts post-I/R. UB, most likely acting via CXCR4, plays a protective role in H/R-induced myocyte apoptosis and myocardial I/R injury via modulation of mitochondrial homeostasis and the mitochondrial death pathway of apoptosis.

Enhanced CAR T cell expansion and prolonged persistence in pediatric patients with ALL treated with a low-affinity CD19 CAR.

Chimeric antigen receptor (CAR)-modified T cells targeting CD19 demonstrate unparalleled responses in relapsed/refractory acute lymphoblastic leukemia (ALL)1-5, but toxicity, including cytokine-release syndrome (CRS) and neurotoxicity, limits broader application. Moreover, 40-60% of patients relapse owing to poor CAR T cell persistence or emergence of CD19- clones. Some factors, including the choice of single-chain spacer6 and extracellular7 and costimulatory domains8, have a profound effect on CAR T cell function and persistence. However, little is known about the impact of CAR binding affinity. There is evidence of a ceiling above which increased immunoreceptor affinity may adversely affect T cell responses9-11. We generated a novel CD19 CAR (CAT) with a lower affinity than FMC63, the high-affinity binder used in many clinical studies1-4. CAT CAR T cells showed increased proliferation and cytotoxicity in vitro and had enhanced proliferative and in vivo antitumor activity compared with FMC63 CAR T cells. In a clinical study (CARPALL, NCT02443831 ), 12/14 patients with relapsed/refractory pediatric B cell acute lymphoblastic leukemia treated with CAT CAR T cells achieved molecular remission. Persistence was demonstrated in 11 of 14 patients at last follow-up, with enhanced CAR T cell expansion compared with published data. Toxicity was low, with no severe CRS. One-year overall and event-free survival were 63% and 46%, respectively.

Discovery of a CD10-negative B-progenitor in human fetal life identifies unique ontogeny-related developmental programs.

Human lymphopoiesis is a dynamic lifelong process that starts in utero 6 weeks postconception. Although fetal B-lymphopoiesis remains poorly defined, it is key to understanding leukemia initiation in early life. Here, we provide a comprehensive analysis of the human fetal B-cell developmental hierarchy. We report the presence in fetal tissues of 2 distinct CD19+ B-progenitors, an adult-type CD10+ve ProB-progenitor and a new CD10-ve PreProB-progenitor, and describe their molecular and functional characteristics. PreProB-progenitors and ProB-progenitors appear early in the first trimester in embryonic liver, followed by a sustained second wave of B-progenitor development in fetal bone marrow (BM), where together they form >40% of the total hematopoietic stem cell/progenitor pool. Almost one-third of fetal B-progenitors are CD10-ve PreProB-progenitors, whereas, by contrast, PreProB-progenitors are almost undetectable (0.53% ± 0.24%) in adult BM. Single-cell transcriptomics and functional assays place fetal PreProB-progenitors upstream of ProB-progenitors, identifying them as the first B-lymphoid-restricted progenitor in human fetal life. Although fetal BM PreProB-progenitors and ProB-progenitors both give rise solely to B-lineage cells, they are transcriptionally distinct. As with their fetal counterparts, adult BM PreProB-progenitors give rise only to B-lineage cells in vitro and express the expected B-lineage gene expression program. However, fetal PreProB-progenitors display a distinct, ontogeny-related gene expression pattern that is not seen in adult PreProB-progenitors, and they share transcriptomic signatures with CD10-ve B-progenitor infant acute lymphoblastic leukemia blast cells. These data identify PreProB-progenitors as the earliest B-lymphoid-restricted progenitor in human fetal life and suggest that this fetal-restricted committed B-progenitor might provide a permissive cellular context for prenatal B-progenitor leukemia initiation.