Thrombotic thrombocytopenic purpura (TTP) is a rare, potentially fatal thrombotic microangiopathy caused by severe ADAMTS13 deficiency. Prompt treatment improves survival; however, reference standard ELISA and FRETS-VWF73 ADAMTS13 activity assays have long turnaround times that necessitate empiric treatment of many patients who ultimately are found not to have TTP. Rapid assays with analytical turnaround times within one hour have recently become available. We conducted a systematic review and meta-analysis of the performance characteristics of rapid assays relative to reference standard assays for ADAMTS13 activity for patients with suspected or confirmed TTP. Nineteen studies representing three rapid ADAMTS13 assays and 4,207 patient samples were included. The HemosIL AcuStar CLIA demonstrated high sensitivity (0.98, 95% CI 0.94 - 1.00), specificity (0.99, 0.97 - 1.00), and positive (0.96, 0.90 - 0.98) and negative predictive value (0.99, 0.99 - 1.00). The Technofluor FRET and Technoscreen assays had sensitivity of 0.93 (0.86 - 0.96) and 0.98 (0.42 - 1.00), specificity of 0.98 (0.95 - 0.99) and 0.87 (0.76 - 0.94), PPV of 0.97 (0.85 - 1.00) and 0.71 (0.59 - 0.80), and NPV of 0.96 (0.93 - 0.98) and 0.99 (0.72 - 1.00), respectively. The proportion of discrepant results (relative to reference standard assays) was 0.04 (0.03 - 0.05) for HemosIL AcuStar, 0.04 (0.02 - 0.06) for Technofluor FRET, and 0.11 (0.07 - 0.16) for the Technoscreen assay. With rapid turnaround time and high sensitivity, the HemosIL AcuStar CLIA appears able to reliably avert empiric plasma exchange, corticosteroids, and caplacizumab in patients without TTP.

Recent studies indicate the human lympho-myeloid restriction process to be a different and more heterogeneous one than historically inferred. Here we describe the development of bulk and clonal culture systems that efficiently support early B-lymphoid differentiation and its use to elucidate the biological and molecular changes that accompany their initial restriction from subsets of CD34+ human cord blood cells with lympho-myeloid-limited potential. Analyses of these changes revealed that the acquisition of B-lymphoid- and neutrophil/monocyte (NM)-restricted properties are accompanied by a concomitantly accelerated and lineage-shared cell cycling activity and loss of self-renewal potential. Single-cell transcriptome analysis identified reduced expression of multiple self-renewal-associated genes and an accompanying heterogeneous activation of lineage-regulatory modules during the production of B, NM and dendritic cell precursors. By applying a novel culture system that supports early human lymphoid differentiation, we uncover a shared mechanism of proliferation control, along with persistent biological and transcriptional heterogeneity in cells undergoing B and NM lineage restriction.

Immune effector cell-associated hematotoxicity (ICAHT) was recently introduced as a distinct toxicity category of CAR-T therapy. While a grading system based solely on neutrophil counts was proposed (hereafter termed N-ICAHT), the prevalence and prognostic impact of thrombocytopenia remains poorly defined. In this multicenter observational study, we systematically examined patterns of thrombocytopenia in 744 patients treated with commercial CD19 CAR-T for B-cell Non-Hodgkin Lymphoma (B-NHL). We developed a grading system termed T-ICAHT with thresholds that closely aligned with N-ICAHT - based on depth, duration and timing of thrombocytopenia. In the core NHL dataset, 43% of patients developed any-grade early T-ICAHT (day 0-30), with 23% developing severe (G3+) manifestations. Late T-ICAHT (day 31-100) was observed in 42% (G3+: 13%). While T-ICAHT and N-ICAHT gradings showed some correlation, considerable discordance was noted. On multivariate analysis, bridging therapy, poor performance status, and high Hematotox scores were associated with increased risk of severe early T-ICAHT. Patients with higher T-ICAHT grades showed increased platelet and red blood cell transfusion burden (p<0.001) and more bleeding events (p=0.01). T-ICAHT grades were inversely associated with overall survival (OS), with landmarked 2-year estimates ranging from 67% (G0), to 48% (G1-2) and 35% (G3+). In multivariable Cox regression analysis, the independent prognostic capacity of T-ICAHT for OS was confirmed. Finally, we validated T-ICAHT's clinical and prognostic utility in 3 external cohorts spanning an additional 599 pediatric and adult patients (NHL, MM, B-ALL), confirming its broad applicability. These findings support integrating T-ICAHT into the ICAHT framework to standardize thrombocytopenia grading in CAR-T recipients.

Hematopoietic stem cells (HSCs) are heterogeneous, and the quality of HSCs - that is, 'transplantability' - is a key determinant for posttransplant hematopoietic reconstitution. However, molecular modalities of high-potency HSCs with superior transplantability still remain poorly understood. Here, we conducted large-scale single-clone serial-transplant experiments and tracked descendant cells of 288 HSC clones to quantify their intrinsic capability for hematopoietic reconstitution. Using integrated single-cell transcriptional, immunophenotypical, and Bayesian dynamic analyses, we uncovered three classes of HSC clones - 'Super', 'Flash', and 'Trickle' - that had higher output in the 1st generation but exhibited markedly different behavior in later generations. The 'Super'-class HSC clones comprised 4% of the HSCs and manifested persistent superior transplantability and balanced myeloid/lymphoid lineage outputs across generations in serial transplants. The 'Super'-class HSCs had a unique molecular signature, including low expression of CD27, that was distinct from previously known 'Classical HSC' signatures. Validation experiments indicated that CD27- HSCs had superior transplantability compared to CD27+ HSCs. Our study asserted an operational definition for 'Super' transplantability of HSCs, defined its molecular program, and suggested new directions for enriching high-potency HSCs in grafts.

Chronic myeloid leukemia (CML) has served as a paradigm for the development of effective initial and next-generation targeted therapies. The availability of five effective and generally well-tolerated BCR::ABL1 tyrosine kinase inhibitors for the treatment of newly diagnosed chronic phase CML offers patients and their treating physicians a welcome luxury of choice. The long-term outlook for newly diagnosed chronic phase CML patients is excellent, with expected survival similar to age-matched controls. However, most patients are expected to require lifelong treatment. As a result, important considerations when choosing frontline treatment include not only treatment efficacy, but also response durability, tolerability, maximizing quality of life, avoidance of serious and irreversible toxicities, the ease of treatment administration and increasingly, the cost of treatment to the patient as well as to society.

Chronic granulomatous disease (CGD) is an inborn error of immunity caused by defects in any one of the 6 subunits (gp91phox, p47phox, p22phox, p67phox, p40phox or chaperone EROS) forming the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase complex 2 (NOX2) and resulting in defective phagocyte-derived reactive oxygen species (ROS) production. Almost 50% of patients with CGD have inflammatory bowel disease (IBD) associated with dysbiosis and age of IBD onset may vary according to CGD genotype. While we previously demonstrated that the intestinal microbiota determines colitis susceptibility in CGD mice, underlying mechanisms remain unknown. We hypothesized that NOX2 defects are associated with distinct intestinal microbiome signatures and immune responses, which impact colitis severity. Chemical colitis susceptibility was evaluated in 2 strains of CGD mice (gp91phox-/- and p47phox-/-) with distinct microbiota, from 2 different animal facilities, while also evaluating the impact of microbiota standardization and colitogenic microbiota transfer on mucosal immune responses at the intestinal barrier. While p47phox-/- and gp91phox-/-mice harbouring colitogenic microbiota had increased colitis severity, the intestinal epithelial cells from p47phox-/- mice produced more ROS which was associated with increased NOX isoform gene expression. In contrast, gp91phox-/- mice had decreased mucin production and a mucosal immune response profile suggestive of increased inflammasome activation at the intestinal barrier compared to control and p47phox-/- mice. Our findings suggest that the microbiota impacts colitis susceptibility in a CGD genotype-specific manner, thereby potentially explaining differences in the timing of IBD onset in patients with different CGD genotypes while identifying potential novel and personalized therapeutic targets.

Richter transformation (RT) is defined as an aggressive lymphoma emerging in patients with chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL). Despite novel therapeutics developed in CLL, RT is associated with poor outcomes. In light of recent progress regarding the diagnostic procedures and therapeutic concepts of RT, an international group of experts, under the coordination of the European Research Initiative on CLL (ERIC), has developed consensus recommendations for clinical procedures and future research on this disease. Patients with RT typically present with a rapid clinical decline, worsening B-symptoms, elevated LDH, and/or rapidly enlarging lymphadenopathy. Workup should include a PET-CT for patients with suspected RT. An excisional biopsy should be taken from an accessible lesion, preferably with the highest FDG avidity, and analyzed for the presence of aggressive lymphoma. The molecular relationship to the original CLL clone(s) should be defined. As no effective standard treatment for RT exists, patients should be treated in a clinical trial. Response of both RT and CLL should be assessed at an early time point, and survival endpoints should be prioritized in trial design. We hope that these recommendations can help to harmonize clinical and translational research and improve outcomes for patients with RT.