FVIII peptides presented on HLA-DP and identification of an A3 domain peptide binding with high affinity to the commonly expressed HLA-DP4.

The development of neutralizing antibodies (inhibitors) against coagulation factor VIII (FVIII) poses a major challenge in hemophilia A (HA) treatment. The formation of FVIII inhibitors is a CD4+ T-cell dependent mechanism which includes antigen presenting cells (APCs), B- and T-helper lymphocytes. APCs present FVIII derived peptides on major histocompatibility complex class II (MHC-II) to CD4+ Tcells.

Exploring red blood cells as an antigen delivery system to modulate the immune response towards FVIII in hemophilia A.

Background: The main complication in hemophilia A treatment is the development of inhibitory antibodies against factor (F)VIII. Immune tolerance induction, the gold standard for eradicating anti-FVIII antibodies, is efficient in only 60% to 80% of cases. This underscores the need for more efficient induction of tolerance in patients with hemophilia A with FVIII inhibitors.

Integrative phosphoproteomic analyses reveal hemostatic-endothelial signaling interplay.

Background: The vascular endothelial cell (EC) monolayer plays a crucial part in maintaining hemostasis. An extensive array of G protein-coupled receptors allows ECs to dynamically act on key hemostatic stimuli such as thrombin and histamine. The impact of these individual stimuli on EC signal transduction has been the subject of various studies, but insight into discordant and concordant EC signaling between different G protein-coupled receptors remains limited.

Plasma Profiling of Acute Myeloid Leukemia With Fever- and Infection-Related Complications During Chemotherapy-Induced Neutropenia.

Background: Acute myeloid leukemia (AML) is a heterogenous and complex blood cancer requiring aggressive treatment. Early identification and prediction of the complications following treatment is vital for effective disease management.

Aims: We explored associations between plasma protein levels and fever- and infection-related complications in 26 AML patients during chemotherapy-induced neutropenia.

Platelet proteomic profiling in sitosterolemia suggests thrombocytopenia is driven by lipid disorder and not platelet aberrations.

Sitosterolemia is a rare autosomal recessive genetic disorder in which patients develop hypercholesterolemia and may exhibit abnormal hematologic and/or liver test results. In this disease, dysfunction of either ABCG5 or ABCG8 results in the intestinal hyperabsorption of all sterols, including cholesterol and, more specifically, plant sterols or xenosterols, as well as in the impaired ability to excrete xenosterols into the bile. It remains unknown how and why some patients develop hematologic abnormalities.

Intestinal tissue-resident memory T cells maintain distinct identity from circulating memory T cells after in vitro restimulation.

Resident memory T (T) cells have been recently established as an important subset of memory T cells that provide early and essential protection against reinfection in the absence of circulating memory T cells. Recent findings showing that T expand in vivo after repeated antigenic stimulation indicate that these memory T cells are not terminally differentiated. This suggests an opportunity for in vitro T expansion to apply in an immunotherapy setting.

SKAP2 acts downstream of CD11b/CD18 and regulates neutrophil effector function.

Background: The importance of CD11b/CD18 expression in neutrophil effector functions is well known. Beyond KINDLIN3 and TALIN1, which are involved in the induction of the high-affinity binding CD11b/CD18 conformation, the signaling pathways that orchestrate this response remain incompletely understood.

Method: We performed an unbiased screening method for protein selection by biotin identification (BioID) and investigated the KINDLIN3 interactome.

Endothelial ICAM-1 Adhesome Recruits CD44 for Optimal Transcellular Migration of Human CTLs.

The endothelial lining of blood vessels is covered with a thin polysaccharide coat called the glycocalyx. This layer of polysaccharides contains hyaluronan that forms a protective coat on the endothelial surface. Upon inflammation, leukocytes leave the circulation and enter inflamed tissue by crossing inflamed endothelial cells, mediated by adhesion molecules such as ICAM-1/CD54.

Multi-omics delineation of cytokine-induced endothelial inflammatory states.

Vascular endothelial cells (ECs) form a dynamic interface between blood and tissue and play a crucial role in the progression of vascular inflammation. Here, we aim to dissect the system-wide molecular mechanisms of inflammatory endothelial-cytokine responses. Applying an unbiased cytokine library, we determined that TNFα and IFNγ induced the largest EC response resulting in distinct proteomic inflammatory signatures.

Time-dependent regulation of cytokine production by RNA binding proteins defines T cell effector function.

Potent T cell responses against infections and malignancies require a rapid yet tightly regulated production of toxic effector molecules. Their production level is defined by post-transcriptional events at 3' untranslated regions (3' UTRs). RNA binding proteins (RBPs) are key regulators in this process.

Mass spectrometry-based analysis on the impact of whole blood donation on the global plasma proteome.

Background: Biomonitoring may provide important insights into the impact of a whole blood donation for individual blood donors.

Study Design And Methods: Here, we used unbiased mass spectrometry (MS)-based proteomics to assess longitudinal changes in the global plasma proteome, after a single blood donation for new and regular donors. Subsequently, we compared plasma proteomes of 76 male and female whole blood donors, that were grouped based on their ferritin and hemoglobin (Hb) levels.

Proteomic landscapes of inherited platelet disorders with different etiologies.

Background: Inherited platelet disorders (IPDs) are a heterogeneous group of rare diseases that are caused by the defects in early megakaryopoiesis, proplatelet formation, and/or mature platelet function. Although genomic sequencing is increasingly used to identify genetic variants underlying IPD, this technique does not disclose resulting molecular changes that impact platelet function. Proteins are the functional units that shape platelet function; however, insights into how variants that cause IPDs impact platelet proteomes are limited.

Memory CD8 T cells upregulate glycolysis and effector functions under limiting oxygen conditions.

Memory CD8 T cells are indispensable for maintaining long-term immunity against intracellular pathogens and tumors. Despite their presence at oxygen-deprived infected tissue sites or in tumors, the impact of local oxygen pressure on memory CD8 T cells remains largely unclear. We sought to elucidate how oxygen pressure impacts memory CD8 T cells arising after infection with Listeria monocytogenes-OVA.

Neutrophil azurophilic granule glycoproteins are distinctively decorated by atypical pauci- and phosphomannose glycans.

While neutrophils are critical first-responders of the immune system, they also cause tissue damage and act in a variety of autoimmune diseases. Many neutrophil proteins are N-glycosylated, a post-translational modification that may affect, among others, enzymatic activity, receptor interaction, and protein backbone accessibility. So far, a handful neutrophil proteins were reported to be decorated with atypical small glycans (paucimannose and smaller) and phosphomannosylated glycans.

Extracellular Vesicles Derived From Adult and Fetal Bone Marrow Mesenchymal Stromal Cells Differentially Promote Expansion of Hematopoietic Stem and Progenitor Cells.

Recently, we and others have illustrated that extracellular vesicles (EVs) have the potential to support hematopoietic stem and progenitor cell (HSPC) expansion; however, the mechanism and processes responsible for the intercellular communication by EVs are still unknown. In the current study, we investigate whether primary human bone marrow derived mesenchymal stromal cells (BMSC) EVs isolated from two different origins, fetal (fEV) and adult (aEV) tissue, can increase the relative low number of HSPCs found in umbilical cord blood (UCB) and which EV-derived components are responsible for HSPC expansion. Interestingly, aEVs and to a lesser extent fEVs, showed supportive expansion capacity of UCB-HSPCs.

Specific proteome changes in platelets from individuals with GATA1-, GFI1B-, and RUNX1-linked bleeding disorders.

Mutations in the transcription factors GATA binding factor 1 (GATA1), growth factor independence 1B (GFI1B), and Runt-related transcription factor 1 (RUNX1) cause familial platelet and bleeding disorders. Mutant platelets exhibit common abnormalities including an α-granule reduction resulting in a grayish appearance in blood smears. This suggests that similar pathways are deregulated by different transcription factor mutations.

Probing activation-driven changes in coagulation factor IX by mass spectrometry.

Background: Activated factor IX (FIXa) is an inefficient enzyme that needs activated factor VIII (FVIII) for full activity. Recently, we identified a network of FVIII-driven changes in FIXa employing hydrogen-deuterium eXchange mass spectrometry (HDX-MS). Some changes also occurred in active-site inhibited FIXa, but others were not cofactor-driven, in particular those within the 220-loop (in chymotrypsin numbering).

N-glycan-mediated shielding of ADAMTS13 prevents binding of pathogenic autoantibodies in immune-mediated TTP.

Immune-mediated thrombotic thrombocytopenic purpura (iTTP) is an autoimmune disorder caused by the development of autoantibodies targeting different domains of ADAMTS13. Profiling studies have shown that residues R568, F592, R660, Y661, and Y665 within exosite-3 of the spacer domain provide an immunodominant region of ADAMTS13 for pathogenic autoantibodies that develop in patients with iTTP. Modification of these 5 core residues with the goal of reducing autoantibody binding revealed a significant tradeoff between autoantibody resistance and proteolytic activity.

Hemolysis in the spleen drives erythrocyte turnover.

Red pulp macrophages (RPMs) of the spleen mediate turnover of billions of senescent erythrocytes per day. However, the molecular mechanisms involved in sequestration of senescent erythrocytes, their recognition, and their subsequent degradation by RPMs remain unclear. In this study, we provide evidence that the splenic environment is of substantial importance in facilitating erythrocyte turnover through induction of hemolysis.

Factor VIII-driven changes in activated factor IX explored by hydrogen-deuterium exchange mass spectrometry.

The assembly of the enzyme-activated factor IX (FIXa) with its cofactor, activated factor VIII (FVIIIa) is a crucial event in the coagulation cascade. The absence or dysfunction of either enzyme or cofactor severely compromises hemostasis and causes hemophilia. FIXa is a notoriously inefficient enzyme that needs FVIIIa to drive its hemostatic potential, by a mechanism that has remained largely elusive to date.

CD29 identifies IFN-γ-producing human CD8 T cells with an increased cytotoxic potential.

Cytotoxic CD8 T cells can effectively kill target cells by producing cytokines, chemokines, and granzymes. Expression of these effector molecules is however highly divergent, and tools that identify and preselect CD8 T cells with a cytotoxic expression profile are lacking. Human CD8 T cells can be divided into IFN-γ- and IL-2-producing cells.

MKL1 deficiency results in a severe neutrophil motility defect due to impaired actin polymerization.

Megakaryoblastic leukemia 1 (MKL1) promotes the regulation of essential cell processes, including actin cytoskeletal dynamics, by coactivating serum response factor. Recently, the first human with MKL1 deficiency, leading to a novel primary immunodeficiency, was identified. We report a second family with 2 siblings with a homozygous frameshift mutation in MKL1.