Mutations in TP53 are mutually exclusive with other known drivers of myeloid transformation and define a distinct molecular subtype within de novo Acute Myeloid Leukemia (AML) that is associated with a complex karyotype, resistance to chemotherapy, and poor prognosis. Although TP53 defects are rare in de novo AML, biallelic mutations are a defining molecular feature of erythroleukemia. The genetic alterations that cooperate with defective TP53 to transform erythroid progenitors remain unknown. We found that loss of BAP1 (BRCA1 Associated Protein-1) co-occurs in one-third of patients with TP53-mutated AML, is associated with an erythroid-primed gene expression signature, and confers an additional adverse effect on overall survival. BAP1 is a tumor suppressor involved in the DNA damage response as well as epigenetic regulation through histone H2AK119 de-ubiquitination. While Bap1KO mice develop myelodysplasia with prominent dyserythropoiesis, combined deletion of Bap1 and Trp53 caused transplantable erythroleukemia, and occasionally mixed AML, mirroring the heterogeneity of human disease. Bulk and single-cell RNA-seq coupled to ChIP-seq in hematopoietic progenitors revealed that Bap1 loss triggers a proinflammatory response and cooperates with Trp53 deficiency to transform erythroid-primed multipotent progenitors. Mechanistically, genomic instability led to the development of erythroleukemia, while epigenetic deregulation caused myelomonocytic skewing suggesting a dichotomous and context dependent role for BAP1. We also demonstrate that BAP1 deficient erythroleukemia is dependent on BCL2L1 expression and is sensitive to BCL-xL inhibitors in vivo.

In inflammation, circulating neutrophils indirectly damage the skeleton by inducing formation of bone-resorbing osteoclasts. However, neutrophil progenitors in marrow have no known physiological function. A bone-protective role for the neutrophil lineage was recently suggested when a profound defect in bone structure was observed in mice with neutropenia due to Granulocyte Colony Stimulating Factor (G-CSF) deletion coupled with STAT3 hyperactivation in bone cells. Here, we tested the existence of this protective effect by manipulating neutrophil progenitors in bone marrow by Ly6G antibody (aLy6G) treatment. Two protocols revealed an inverse relationship between marrow neutrophil progenitors and osteoclasts. Two weeks of aLy6G treatment increased marrow immature neutrophils by 25% and halved osteoclast mRNA markers in cortical bone. In contrast, coupling six weeks of aLy6G with anti-rat IgG2a to maintain antigenicity reduced marrow pre-neutrophils by 50%. This doubled trabecular osteoclast surface, halved trabecular bone mass, and significantly reduced high density bone mass both in control mice, and in mice with bone-specific STAT3 hyperactivation. In culture, isolated pre-neutrophils dose-dependently inhibited osteoclastogenesis independent of direct contact. We conclude that neutrophil progenitors directly inhibit osteoclast formation by releasing soluble factors. This identifies a novel action of hematopoietic cells in marrow to protect bone structure.

Platelet shape and volume changes are early mechanical events contributing to platelet activation and thrombosis. Here, we identify single-nucleotide polymorphisms in Leucine-Rich Repeat Containing 8 (LRRC8) protein subunits that form the Volume-Regulated Anion Channel (VRAC) which are independently associated with altered mean platelet volume. LRRC8A is required for functional VRAC in megakaryocytes (MKs) and regulates platelet volume, adhesion, and agonist-stimulated activation, aggregation, ATP secretion and calcium mobilization. MK-specific LRRC8A conditional knockout mice have reduced laser-injury induced cremaster arteriolar thrombus formation and prolonged FeCl3 induced carotid arterial thrombosis without affecting bleeding times. Mechanistically, platelet LRRC8A mediates swell-induced cytosolic ATP release to amplify agonist-stimulated calcium-PI3K-AKT signaling. Small-molecule LRRC8 channel inhibitors recapitulate defects observed in LRRC8A-null platelets in vitro and in vivo. These studies identify the mechanoresponsive LRRC8 channel complex as an ATP release channel in platelets which positively regulates platelet function and thrombosis, providing a proof-of-concept for a novel anti-thrombotic drug target.

Disease-defining signatures in lymphomas, driven by intricate molecular mechanisms, have advanced molecular taxonomies, refined classification, and may guide clinical management; however, the role of these signatures in driving disease hallmarks including subtype-specific organotropism remains largely unexplored. Primary mediastinal large B-cell lymphoma (PMBCL) is an exemplary lymphoma characterized by disease manifestations in the thymic niche, unique genetic alterations and immune escape. Here, we identified IRF4-C99R mutations uniquely occurring in PMBCL through mutational meta-analysis of large-scale datasets. Our functional studies, integrating multi-omics approaches with genome editing in PMBCL cells, revealed that IRF4-C99R contributes to a differentiation block phenotype. Specifically, we showed that IRF4-C99R reduces its binding to the ISRE motif within PRDM1, which encodes a key transcriptional regulator of B-cell differentiation, resulting in decreased PRDM1 expression. Additionally, IRF4-C99R suppresses TNIK, a key IFNγ pathway regulator, by impairing ISRE motif binding, thereby reducing IFNγ signaling and increasing thymus and activation-regulated chemokine (TARC) expression, which drives TARC-mediated chemotaxis of T regulatory cells. We also revealed that IRF4-C99R upregulates Ephrin Type-B Receptor 1 (EPHB1) through non-canonical AICE motif binding, and showed that overexpression of EPHB1 in an immunocompetent syngeneic lymphoma model influenced organotropism to favor thymic localization, without affecting tumor burden in other organs. IRF4-C99R mutation-induced phenotypes were validated in primary PMBCL tissues using single-nuclei RNA sequencing, confirming that the molecular mechanisms observed in vitro align with the pathophysiology of PMBCL in patients. Together, these findings demonstrate how a single genetic mutation orchestrates the coordinated regulation of hallmark traits including thymus-specific tropism in PMBCL.

Anemia of inflammation (AI) is the second most common form of anemia and is prevalent in patients with chronic inflammatory states, such as infection, autoimmunity, and cancer. Interleukin 6 (IL6) is well-known to induce the iron-sequestering hormone hepcidin, which results in iron-restricted anemia. The contributions of other pro-inflammatory cytokines such as tumor necrosis factor-α (TNFα) and interferon-γ (IFNγ) are less understood in the pathophysiology of AI. This study investigated the role of TNFα in a mouse model of AI by administering heat-killed Brucella Abortus (HKBA) to germline TNFα knockout (KO) mice. We hypothesized that TNFα possessed an important role in restoring steady-state erythropoiesis after inflammatory insult. TNFαKO injected with HKBA displayed a chronic anemia, with elevated pro-inflammatory IL12p40 and IFNγ cytokines that did not resolve. However, IFNγKO and TNFαKO/FNγKO double knock-out (DKO) mice showed reduced inflammation and anemia following HKBA administration. Since IFNγKO displayed normal serum TNFα and IL12p40 levels, we hypothesized that the persistent anemia was IFNγ-induced and TNFα was necessary for AI cessation. However, treatment with recombinant TNFα (rTNFα) accelerated death, while reducing IFNγ using an anti-IFNγ antibody (Ab) only briefly improved anemia. Only the combination of both the Ab and rTNFα together reversed the hyper-inflammatory phenotype, restored erythropoiesis, and prevented death of TNFαKO+HKBA mice. Our data provides compelling evidence for an anti-inflammatory role of TNFα that is necessary for the restoration of erythropoiesis and mitigation of pro-inflammatory IFNγ action in a mouse model of AI.

An acute inflammatory response to infection or sterile injury involves an adequate activation and recruitment of leukocytes. Activation of β2-integrins is required for neutrophil recruitment and is also mandatory for various neutrophil cell-intrinsic functions. GTPases are key regulators of the actin cytoskeleton and are required for β2-integrin activation. MyosinIXb (Myo9b), a Rho GTPase-activating protein, is essential for regulating Rho activity in neutrophils. Yet, the exact molecular mechanism how Myo9b regulates β2-integrin activity and neutrophil recruitment into inflamed tissue is unknown. We demonstrate that Myo9b deficiency causes RhoA overactivation, increases actin cytoskeleton rearrangement in neutrophils, decreases neutrophil recruitment into the kidney and improves kidney function in murine models of acute kidney injury. Loss of Myo9b also affects neutrophil effector functions and causes increased rolling velocity, decreased adhesion, impaired crawling, and strongly reduced transmigration of neutrophils in vivo. Mechanistically, Myo9b regulates RhoA activity which is required for chemokine- and selectin-induced talin-1 recruitment to β2-integrins. Thus, Myo9b is a crucial regulator of important signaling pathways in neutrophils and is required for an adequate immune response triggered by chemokines and selectins.

Rapid CD137 upregulation on alloreactive T-cells upon allogeneic stimulation suggests that their selective elimination could prevent acute graft-versus-host disease (aGVHD) after allogeneic hematopoietic stem cell transplantation (HCT). Here, we developed a novel aGVHD prophylactic regimen consisting of a single dose of an anti-CD137 antibody-drug conjugate (CD137-ADC) administered on the day of transplant without additional immunosuppression. The CD137-ADC depleted both human and non-human primate (NHP) activated T-cells and proved highly effective in preventing xenogeneic aGVHD in mice receiving human peripheral blood mononuclear cells (PBMC), as well as in NHP undergoing MHC-haploidentical HCT. Flow cytometry analysis of NHP T-cells indicated specific depletion of activated PD-1+ CD4 and CD8 T-cells, while sparing naïve and PD-1-OX40+ memory T-cell subsets during the first week after HCT. CD137-ADC-treated NHP recipients demonstrated robust hematopoietic and immune reconstitution. Hallmarks of T-cell recovery after CD137-ADC, which were associated with long-term aGVHD-free survival, included reconstitution of CD4 memory T-cells expressing TRAIL, terminally-differentiated CD8 T-cells expressing CX3CR1, and CD4 FoxP3+ Tregs - cell types not expected to be involved in aGVHD pathogenesis. CD137-ADC-treated recipients demonstrated a higher risk of reactivation of rhLCV (the rhesus macaque EBV analogue), which was associated with reconstitution of follicular helper T-cells, interferon signaling-associated memory, and gamma-delta T-cell subsets. This reactivation was controllable with rituximab administration. These results document effective depletion of alloreactive T-cells and prevention of aGVHD following a single dose of CD137-ADC, suggesting that clinical translation should be carefully explored.

Cellular therapies targeting B-cell maturation antigen have shown promise in controlled clinical trials, but their impact in broader, diverse patient populations remains underexplored. This study examines the real-world efficacy and safety in 343 triple-class exposed patients with relapsed and refractory multiple myeloma (RRMM) who received idecabtagene vicleucel (ide-cel, n=266) or ciltacabtagene autoleucel (cilta-cel, n=77) after more than three prior lines of therapy in Germany. Cilta-cel as compared to ide-cel, demonstrated superior outcomes, achieving a higher overall response rate (94% vs. 82%) and 10-month progression-free survival (PFS, 76% vs. 47%). Cilta-cel also led to higher complete response (CR, (61% vs. 39%) and improved response conversion, with more patients achieving CR after starting from less than CR pre-CAR T. For those attaining CR post-therapy, cilta-cel showed longer PFS, especially in patients who entered treatment with a partial response or worse. Cytokine release syndrome was observed in 85% of cilta-cel and 81% of ide-cel cases, predominantly low-grade. Immune effector cell-associated neurotoxicity syndrome was more common with cilta-cel (25% vs. 15%), although non-relapse mortality at 10 months was comparable between therapies (7% vs. 5%). Weighted multivariable analysis after propensity score matching confirmed significant advantage in terms of PFS for cilta-cel, with a hazard ratio of 0.48. Overall, outcomes in our registry analysis were comparable to the pivotal trials that led to approval of the respective agents. Cilta-cel demonstrated a greater capacity for response conversion and durable remission. These findings underscore the need for individualized CAR T therapy selection to optimize patient outcomes.

CD19-directed chimeric antigen receptor (CAR) T-cell therapy has revolutionized the treatment of relapsed/refractory B-cell non-Hodgkin lymphoma (B-NHL) and recently showed effects in autoimmune diseases such as systemic lupus erythematosus (SLE). Despite high levels of inflammation, toxicity appeared to differ in SLE and B-NHL. We therefore compared CAR T-cell kinetics and treatment-related side-effects to better define the distinct toxicity profiles. Contrary to similar CAR T-cell expansion, SLE patients revealed lower incidence and severity of cytokine-release syndrome, immune-effector cell-associated neurotoxicity syndrome, and immune-effector cell-associated hematotoxicity. While neutrophil nadir was lower in SLE patients after therapy, platelets remained close to normal and hematotoxicity was shorter in SLE than in B-NHL. Reduced hematotoxicity correlated with lower acute phase inflammation, better hematological reserve prior to CAR T-cell therapy, and distinct serum cytokine profiles. Interestingly, CAR T-cell persistence was consistently shorter and reconstitution of conventional T- and B-cells was faster in SLE. In both cohorts, B-cell reconstitution correlated with functional CD4+ T-cell recovery, indicating a general biological process of hematopoietic and immune system regeneration. In summary, similar lymphodepletion and CAR T-cell pharmacokinetics resulted in distinct toxicity, demonstrating a favorable side effect profile of CAR T-cell therapy in SLE including faster recovery of the adaptive immune system.

Clonal hematopoiesis of indeterminate potential (CHIP) is associated with increased mortality and malignancy risk, yet the determinants of clonal expansion remain poorly understood. We performed sequencing at >4,000x depth of coverage for CHIP mutations in 6,976 postmenopausal women from the Women's Health Initiative at two timepoints: the WHI baseline exam and approximately 16 years later at the Long Life Study (LLS) visit. Among 3,685 CH mutations detected at baseline (VAF ≥ 0.5%), 24% were not detected at LLS, 26% were micro-CH at LLS (0.5% ≤ VAF < 2%), and 50% were CHIP (VAF ≥ 2%). We confirmed that clonal expansion is highly dependent on initial clone size and CHIP driver gene, with SF3B1 and JAK2 mutations exhibiting the fastest growth rate. We identified germline variants in TERT, IL6R, TCL1A, and MSI2 that modulate clonal expansion rate. Measured baseline leukocyte telomere length showed differential effects on incident CHIP risk, with shorter baseline leukocyte telomere length predisposing to incident PPM1D mutations and longer baseline leukocyte telomere length favoring incident DNMT3A mutations. We discovered that the IL6R missense variant p.Asp358Ala specifically impairs TET2 clonal expansion, supported by direct measurements of soluble interleukin-6 receptor and interleukin-6. Faster clonal growth rate was associated with increased risk of cytopenia, leukemia, and all-cause mortality. Notably, CHIP clonal expansion rate mediated 34.4% and 43.7% of the Clonal Hematopoiesis Risk Score's predictive value for leukemia and all-cause mortality, respectively. These findings reveal key biological determinants of CHIP progression and suggest that incorporating growth rate measurements could enhance risk stratification.

Patients with follicular lymphoma (FL) who experience disease progression within 24 months of diagnosis (POD24) have a lower survival. Positron emission tomography (PET) response and circulating tumor DNA (ctDNA) residual disease (MRD) assessment at end of induction therapy (EOI) may allow their early identification. A representative cohort of 141 patients from the RELEVANCE phase III trial with both available serum samples for ctDNA testing and PET images at randomization and at EOI (week 24) was investigated. Twelve percent were POD24. CtDNA was analyzed using a customized 130-kilobase capture panel, with Phased Variant (PV) enriched regions representing 39% of the panel. CtDNA was detected in 140 patients (99.3%) at baseline. To optimize specificity, only PVs, found in 124 patients (88%), were considered for ctDNA MRD assessment at EOI. Median PFS from EOI was not reached (NR) for the 112 patients with undetected ctDNA at EOI versus 17.7 months (95%CI : 1.4-NA) for patients ctDNA MRD (+) (p=0.0038). Similarly, median PFS was NR for the 104 patients with undetected disease on PET at EOI versus 28.3 months (95%CI : 2.9-NR, p=0.0002) for patients with PET(+). Both tests had a negative predictive value (NPV) above 90% for POD24. The positive predictive value was 58.3% for ctDNA MRD and 45% for PET but increased to 85.7% when both parameters were combined, without alteration of NPV. These data show that the combination of PET response and ctDNA MRD at EOI allows for an early prediction of POD24 which may lead to a preemptive treatment decision.

In retrospective studies, autologous stem cell transplantation (ASCT) conditioning with intravenous busulfan and melphalan (BUMEL) led to longer progression-free survival (PFS) than melphalan alone (MEL200). We compared BUMEL vs. MEL200 outcomes in newly diagnosed multiple myeloma (NDMM) patients receiving intensified bortezomib, lenalidomide and dexamethasone (VRD) induction and consolidation therapy. The GEM12 phase III trial enrolled 458 patients (from 2013 to 2015) who were randomized to BUMEL (n=230) or MEL200 (n=228) conditioning after induction with six reinforced VRD cycles and followed by two similar VRD consolidation cycles. The primary endpoint was PFS, including subgroup analyses by International Staging System (ISS) stages and high-risk genetic abnormalities. Randomization used an open-label 2×2 factorial design and 1:1:1:1 allocation ratio to ensure the balance between the GEM12 and the subsequent phase III GEM14 maintenance trial. After 2 years of maintenance, the global 10⁻⁶ MRD-negative rate was 63%, (68% BUMEL vs. 58% MEL200; OR 1.51, P= 0.035). The PFS was not significantly better in the BUMEL vs. MEL200, even though it was almost 16 months longer (median PFS 89 vs. 73.1 months; HR 0.89, 95%CI, 0.70-1.14, P= 0.3). BUMEL showed benefits in ISS stages 2/3, t(14;16), and del(1p). In a combined subgroup jointly considering patients with ISS2/3 treated with BUMEL and patients with ISS1 treated with MEL200 the median PFS was 96 months (95%CI, 76-NE). No safety concerns emerged. After a median follow-up of 8.4 years, GEM2012 reported one of the longest PFS durations in NDMM patients, with BUMEL significantly favoring advanced ISS stages. The trial is registered at ClinicalTrials.gov (NCT01916252) and EudraCT (2012-005683-10).

Blood transfusions save millions of lives worldwide each year, yet formation of antibodies against non-self antigens remains a significant problem, particularly in frequently transfused patients. We designed and tested the Universal Blood Donor Typing (UBDT_PC1) array for automated high-throughput simultaneous typing of human erythroid, platelet, leukocyte, and neutrophil antigens (HEA, HPA, HLA, and HNA, respectively) to support selection of blood products matched beyond ABO/Rh. Typing samples from 6946 donors of European, African, Admixed American, South Asian, and East Asian ancestry at two different laboratories showed a genotype reproducibility of ≥99% for 17 244 variants, translating to 99.98%, 99.90%, and 99.93% concordance across 338 372 HEA, 53 270 HPA, and 107 094 HLA genotypes, respectively. Compared to previous clinical typing data, concordance was 99.9% and 99.6% for 245 874 HEA and 3726 HPA comparisons, respectively. HLA types were 99.1% concordant with clinical typing across 8130 comparisons, with imputation accuracy higher in Europeans versus non-Europeans. Seven variant RHD alleles, a GYPB deletion underlying the U- phenotype, and 14 high-frequency antigen negative types were also detected. Beyond blood typing, hereditary hemochromatosis-associated HFE variants were identified in 276 donors. We found that the UBDT_PC1 array can reliably type a wide range of blood cell antigens across diverse ancestries. Reproducibility and accuracy were retained when transfusion-relevant targets from the UBDT_PC1 array were incorporated into the UKBB_v2.2 genome-wide typing array. The results represent the potential for significant advancement towards improved patient care by reducing harm in transfused patients through extended matching.

AL amyloidosis is a disorder characterized by expansion of clonal plasma cells in the bone marrow and distant end organ damage mediated by misfolded immunoglobulin free light chains. There are currently limited data regarding the functional characteristics of AL amyloidosis plasma cells and their surrounding bone marrow microenvironment. We performed 5' single cell RNA sequencing on newly diagnosed, treatment naïve AL amyloidosis patients and healthy subjects. We identified generalized suppression of normal bone marrow hematopoiesis with distinct expansion of monocytes and subsets of CD4+ T cells in AL amyloidosis patients. We detected significant transcriptional changes broadly occurring among immune cells with increased TNF-a signaling and interferon response accompanied by increased inflammatory response in bone marrow plasma as measured via quantitative proteomics with specific elevation of co-stimulatory molecule soluble CD276 (sB7-H3). A transcriptionally distinct population of non-malignant plasma cells was disproportionately expanded in AL amyloidosis patients and characterized by increased expression of CRIP1. Finally, clonal AL amyloidosis plasma cells were identified based on their unique VDJ rearrangement and showed increased expression of genes involved in proteostasis when compared to autologous, polyclonal plasma cells. Inter-patient transcriptional heterogeneity was evident, with transcriptional states reflective of common genomic translocations easily identifiable. This study defines the transcriptional characteristics of AL amyloidosis plasma cells and their surrounding bone marrow microenvironment with identification of altered genes previously involved in the pathogenesis of other protein deposition disorders. Our data provide the rationale for functional validations of these genes in future studies.

TET2 is among the most commonly mutated genes in both clonal hematopoiesis and myeloid malignancies, thus, the ability to identify selective dependencies in TET2 deficient cells has broad translational significance. Here, we identify regulators of Tet2 knockout (KO) hematopoietic stem and progenitor cell (HSPC) expansion using an in vivo CRISPR-Cas9 KO screen, in which nucleotide barcoding enabled large-scale clonal tracing of Tet2 deficient HSPCs in a physiological setting. Our screen identified candidate genes, including Ncoa4, that are selectively required for Tet2 KO clonal outgrowth compared to wild-type (WT). Ncoa4 targets ferritin for lysosomal degradation (ferritinophagy), maintaining intracellular iron homeostasis by releasing labile iron (Fe2+) in response to cellular demands. In Tet2-deficient HSPCs, increased mitochondrial ATP production correlates with increased cellular iron requirements, and in turn, promotes Ncoa4-dependent ferritinophagy. Restricting iron availability reduces Tet2 KO stem cell numbers, revealing a dependency in TET2-mutated myeloid neoplasms.

Monoclonal antibodies targeting CD38 are a therapeutic mainstay in multiple myeloma (MM). While they have contributed to improved outcomes, most patients still experience disease relapse, and little is known about tumor-intrinsic mechanisms of resistance to these drugs. Antigen escape has been implicated as a mechanism of tumor cell evasion in immunotherapy. Yet, it is unknown whether MM cells can develop permanent resistance to anti-CD38 antibodies by acquiring genomic events leading to biallelic disruption of the CD38 gene locus. Here, we analyzed whole genome and whole exome sequencing data from 701 newly diagnosed patients, 67 patients at relapse with naivety to anti-CD38 antibodies, and 50 patients collected at relapse following anti-CD38 antibodies. We report a loss of CD38 in 20% (10/50) of patients post-CD38 therapy, three of which exhibited a loss of both copies. Two of these cases showed convergent evolution where distinct subclones independently acquired similar advantageous variants. Functional studies on missense mutations involved in biallelic CD38 events revealed that two variants, L153H and C275Y, decreased binding affinity and antibody-dependent cellular cytotoxicity of the commercial antibodies Daratumumab and Isatuximab. However, a third mutation, R140G, conferred selective resistance to Daratumumab, while retaining sensitivity to Isatuximab. Clinically, patients with MM are often rechallenged with CD38 antibodies following disease progression and these data suggest that next generation sequencing may play a role in subsequent treatment selection for a subset of patients.

Developing anti-FVIII inhibitory antibodies (inhibitors) is a significant complication of FVIII protein replacement therapy in hemophilia A. Our previous study demonstrated that follicular helper T (TFH) cells play a critical role in FVIII inhibitor development. Follicular regulatory T (TFR) cells are a subset of Foxp3+ T cells recently identified in the germinal center that can modulate TFH cell activation of B cells and antibody development. Here, we report that FVIII immunization significantly increases the TFR cells in the spleens of FVIII inhibitor-producing FVIIInull mice compared to saline-treated controls and non-inhibitor-producing animals. The TFH/TFR ratio significantly increased in FVIII inhibitor-producing mice. The emergence of TFR cells correlated with titers of FVIII inhibitors in FVIII-immunized mice. Using TFR-deficient Foxp3Cre+Bcl6fl/fl (Bcl6FC) mice, we found that the loss of TFR cells led to significantly decreased FVIII inhibitors compared to wild-type (WT) mice upon FVIII immunization (24±16 and 131±114 BU/ml, respectively) but not total anti-FVIII IgG levels and that TFR cells regulated IgG subclass switching and FVIII-specific B cell responses. Interestingly, upon FVIII immunization, mice with phosphatase Pten deficiency in Foxp3+ cells (Foxp3Cre+Ptenfl/fl), a model with augmented TFR cells, developed markedly lower FVIII inhibitor titers (8.1±8.6 BU/ml) than WT controls. When CD4Cre+Bcl6fl/fl mice, a TFH and TFR deficient model, were immunized with FVIII, none of the animals developed FVIII inhibitors. In conclusion, FVIII immunization induces TFR cell activation and expansion. TFR cells have a dual function in regulating the development of FVIII inhibitors, and the TFH/TFR pathway is pivotal in FVIII inhibitor development in mice.

Although allogeneic HCT is a leading treatment approach for myeloid malignancies, challenges in its immune biology and in treatment approaches remain. In the past decade major advances in the knowledge of mechanisms of graft-versus host disease (GvHD) has allowed development of new treatments both for GvHD prophylaxis and treatment. However, although successes did occur, failure did as well. Reasons for failure can be linked either to incomplete understanding of the pathophysiology of GVHD, or, in some cases, to errors in the design of clinical trials. Better GVHD prophylaxes and disease control have likely led to decreased non relapse mortality (NRM). However, while NRM rates have decreased, rates of relapse of the original malignancy have not significantly improved. Our current understanding of the biology of the graft-versus leukemia effect (GvL) still lag beyond that of GvHD, and treatment approaches to manipulate the GvL effect remain limited. The reasons for such a lag are numerous, but improved knowledge of the biology of hematological malignancies open the gate to new developments, providing that we can better understand the interplay between the immune system with leukemic clones. From a therapeutical perspective, much attention has been paid to the results from randomized clinical trials and from a biological perspective on recent discoveries, especially in the human setting. The objective of this perspective is to analyze what are the current challenges in the biology and treatment of GvHD and GvL and to provide a personal view on how some biological and therapeutic issues could be approached.

Disease response and progression assessment in multiple myeloma (MM) is based on various measurements of monoclonal protein (serum and urine protein electrophoresis, serum free light chain (FLC, and or quantitative immunoglobulins). Currently, the IMWG consensus response criteria require two sequential assessments of any one marker made at any time before confirmation of disease progression and the institution of any new therapy. However, this can be cumbersome in clinical trials. Herein, we hypothesized that if two markers meet the progression criteria simultaneously, a repeat of either will not be necessary for confirmation. We retrospectively studied all sequential patients with myeloma enrolled in clinical trials at Mayo Clinic. We identified 583 episodes of confirmed progression in our study. Among the 583 progression episodes, nearly 70% (sensitivity of the simultaneous criteria) met the two simultaneous variable criteria at the first testing, indicating progression. Conversely, among 413 patients who met progression criteria by two simultaneous values, 98% (specificity of the simultaneous criteria) of patients subsequently had confirmed progression by sequential values. In summary, for patients with two disease burden markers meeting the simultaneous progression criteria, sequential assessment either one for confirmation may not be necessary to determine disease progression.

The human genome contains regulatory DNA elements, enhancers, that can activate gene transcription over long chromosomal distances. Here, we show that enhancer distance can be critical for gene silencing. We demonstrate that linear recruitment of the normally distal strong HBB enhancer to developmentally silenced embryonic HBE or fetal HBG promoters, through deletion or inversion of intervening DNA sequences, results in their strongly reactivated expression in adult erythroid cells and ex vivo differentiated hematopoietic stem and progenitor cells. A similar observation is made in the HBA locus, where deletion-to-recruit of the distal enhancer strongly reactivates embryonic HBZ expression. Overall, our work assigns function to seemingly non-regulatory genomic segments: by providing linear separation they may support genes to autonomously control their transcriptional response to distal enhancers.