N-MYC regulates cell survival via eIF4G1 in inv(16) acute myeloid leukemia.

N-MYC (encoded by MYCN) is a critical regulator of hematopoietic stem cell function. While the role of N-MYC deregulation is well established in neuroblastoma, the importance of N-MYC deregulation in leukemogenesis remains elusive. Here, we demonstrate that N-MYC is overexpressed in acute myeloid leukemia (AML) cells with chromosome inversion inv(16) and contributes to the survival and maintenance of inv(16) leukemia. We identified a previously unknown MYCN enhancer, active in multiple AML subtypes, essential for MYCN mRNA levels and survival in inv(16) AML cells. We also identified eukaryotic translation initiation factor 4 gamma 1 (eIF4G1) as a key N-MYC target that sustains leukemic survival in inv(16) AML cells. The oncogenic role of eIF4G1 in AML has not been reported before. Our results reveal a mechanism whereby N-MYC drives a leukemic transcriptional program and provides a rationale for the therapeutic targeting of the N-MYC/eIF4G1 axis in myeloid leukemia.

Rapid transient and longer-lasting innate cytokine changes associated with adaptive immunity after repeated SARS-CoV-2 BNT162b2 mRNA vaccinations.

Introduction: Cytokines and chemokines play an important role in shaping innate and adaptive immunity in response to infection and vaccination. Systems serology identified immunological parameters predictive of beneficial response to the BNT162b2 mRNA vaccine in COVID-19 infection-naïve volunteers, COVID-19 convalescent patients and transplant patients with hematological malignancies. Here, we examined the dynamics of the serum cytokine/chemokine responses after the 3rd BNT162b2 mRNA vaccination in a cohort of COVID-19 infection-naïve volunteers. Methods: We measured serum cytokine and chemokine responses after the 3rd dose of the BNT162b2 mRNA (Pfizer/BioNtech) vaccine in COVID-19 infection-naïve individuals by a chemiluminescent assay and ELISA. Anti-Spike binding antibodies were measured by ELISA. Anti-Spike neutralizing antibodies were measured by a pseudotype assay. Results: Comparison to responses found after the 1st and 2nd vaccinations showed persistence of the coordinated responses of several cytokine/chemokines including the previously identified rapid and transient IL-15, IFN-γ, CXCL10/IP-10, TNF-α, IL-6 signature. In contrast to the transient (24hrs) effect of the IL-15 signature, an inflammatory/anti-inflammatory cytokine signature (CCL2/MCP-1, CCL3/MIP-1α, CCL4/MIP-1ß, CXCL8/IL-8, IL-1Ra) remained at higher levels up to one month after the 2nd and 3rd booster vaccinations, indicative of a state of longer-lasting innate immune change. We also identified a systemic transient increase of CXCL13 only after the 3rd vaccination, supporting stronger germinal center activity and the higher anti-Spike antibody responses. Changes of the IL-15 signature, and the inflammatory/anti-inflammatory cytokine profile correlated with neutralizing antibody levels also after the 3rd vaccination supporting their role as immune biomarkers for effective development of vaccine-induced humoral responses. Conclusion: These data revealed that repeated SARS-Cov-2 BNT162b2 mRNA vaccination induces both rapid transient as well as longer-lasting systemic serum cytokine changes associated with innate and adaptive immune responses. Clinical trial registration: Clinicaltrials.gov, identifier NCT04743388.

A spatial sequencing atlas of age-induced changes in the lung during influenza infection.

Influenza virus infection causes increased morbidity and mortality in the elderly. Aging impairs the immune response to influenza, both intrinsically and because of altered interactions with endothelial and pulmonary epithelial cells. To characterize these changes, we performed single-cell RNA sequencing (scRNA-seq), spatial transcriptomics, and bulk RNA sequencing (bulk RNA-seq) on lung tissue from young and aged female mice at days 0, 3, and 9 post-influenza infection. Our analyses identified dozens of key genes differentially expressed in kinetic, age-dependent, and cell type-specific manners. Aged immune cells exhibited altered inflammatory, memory, and chemotactic profiles. Aged endothelial cells demonstrated characteristics of reduced vascular wound healing and a prothrombotic state. Spatial transcriptomics identified novel profibrotic and antifibrotic markers expressed by epithelial and non-epithelial cells, highlighting the complex networks that promote fibrosis in aged lungs. Bulk RNA-seq generated a timeline of global transcriptional activity, showing increased expression of genes involved in inflammation and coagulation in aged lungs. Our work provides an atlas of high-throughput sequencing methodologies that can be used to investigate age-related changes in the response to influenza virus, identify novel cell-cell interactions for further study, and ultimately uncover potential therapeutic targets to improve health outcomes in the elderly following influenza infection.

Endothelial Rap1B mediates T-cell exclusion to promote tumor growth: a novel mechanism underlying vascular immunosuppression.

Overcoming vascular immunosuppression: lack of endothelial cell (EC) responsiveness to inflammatory stimuli in the proangiogenic environment of tumors, is essential for successful cancer immunotherapy. The mechanisms through which Vascular Endothelial Growth Factor A(VEGF-A) modulates tumor EC response to exclude T-cells are not well understood. Here, we demonstrate that EC-specific deletion of small GTPase Rap1B, previously implicated in normal angiogenesis, restricts tumor growth in endothelial-specific Rap1B-knockout (Rap1BiΔEC) mice. EC-specific Rap1B deletion inhibits angiogenesis, but also leads to an altered tumor microenvironment with increased recruitment of leukocytes and increased activity of tumor CD8+ T-cells. Depletion of CD8+ T-cells restored tumor growth in Rap1BiΔEC mice. Mechanistically, global transcriptome and functional analyses indicated upregulation of signaling by a tumor cytokine, TNF-α, and increased NF-κB transcription in Rap1B-deficient ECs. Rap1B-deficiency led to elevated proinflammatory chemokine and Cell Adhesion Molecules (CAMs) expression in TNF-α stimulated ECs. Importantly, CAM expression was elevated in tumor ECs from Rap1BiΔEC mice. Significantly, Rap1B deletion prevented VEGF-A-induced immunosuppressive downregulation of CAM expression, demonstrating that Rap1B is essential for VEGF-A-suppressive signaling. Thus, our studies identify a novel endothelial-endogenous mechanism underlying VEGF-A-dependent desensitization of EC to proinflammatory stimuli. Significantly, they identify EC Rap1B as a potential novel vascular target in cancer immunotherapy.

Low Spike Antibody Levels and Impaired BA.4/5 Neutralization in Patients with Multiple Myeloma or Waldenstrom's Macroglobulinemia after BNT162b2 Booster Vaccination.

Patients with symptomatic monoclonal gammopathies have impaired humoral responses to COVID-19 vaccination. Their ability to recognize SARS-CoV-2 Omicron variants is of concern. We compared the response to BNT162b2 mRNA vaccinations of patients with multiple myeloma (MM, n = 60) or Waldenstrom's macroglobulinemia (WM, n = 20) with healthy vaccine recipients (n = 37). Patient cohorts on active therapy affecting B cell development had impaired binding and neutralizing antibody (NAb) response rate and magnitude, including several patients lacking responses, even after a 3rd vaccine dose, whereas non-B cell depleting therapies had a lesser effect. In contrast, MM and WM cohorts off-therapy showed increased NAb with a broad response range. ELISA Spike-Receptor Binding Domain (RBD) Ab titers in healthy vaccine recipients and patient cohorts were good predictors of the ability to neutralize not only the original WA1 but also the most divergent Omicron variants BA.4/5. Compared to WA1, significantly lower NAb responses to BA.4/5 were found in all patient cohorts on-therapy. In contrast, the MM and WM cohorts off-therapy showed a higher probability to neutralize BA.4/5 after the 3rd vaccination. Overall, the boost in NAb after the 3rd dose suggests that repeat vaccination of MM and WM patients is beneficial even under active therapy.

Endocytosis of the thrombopoietin receptor Mpl regulates megakaryocyte and erythroid maturation in mice.

Dnm2fl/fl Pf4-Cre (Dnm2Plt-/- ) mice lacking the endocytic GTPase dynamin 2 (DNM2) in platelets and megakaryocytes (MKs) develop hallmarks of myelofibrosis. At the cellular level, the tyrosine kinase JAK2 is constitutively active but decreased in expression in Dnm2Plt-/- platelets. Additionally, Dnm2Plt-/- platelets cannot endocytose the thrombopoietin (TPO) receptor Mpl, leading to elevated circulating TPO levels. Here, we assessed whether the hyperproliferative phenotype of Dnm2Plt-/- mice was due to JAK2 constitutive activation or to elevated circulating TPO levels. In unstimulated Dnm2Plt-/- platelets, STAT3 and, to a lower extent, STAT5 were phosphorylated, but their phosphorylation was slowed and diminished upon TPO stimulation. We further crossed Dnm2Plt-/- mice in the Mpl-/- background to generate Mpl-/-Dnm2Plt-/- mice lacking Mpl ubiquitously and DNM2 in platelets and MKs. Mpl-/- Dnm2Plt-/- platelets had severely reduced JAK2 and STAT3 but normal STAT5 expression. Mpl-/- Dnm2Plt-/- mice had severely reduced bone marrow MK and hematopoietic stem and progenitor cell numbers. Additionally, Mpl-/- Dnm2Plt-/- mice had severe erythroblast (EB) maturation defects, decreased expression of hemoglobin and heme homeostasis genes and increased expression of ribosome biogenesis and protein translation genes in spleen EBs, and developed anemia with grossly elevated plasma erythropoietin (EPO) levels, leading to early fatality by postnatal day 25. Mpl-/- Dnm2Plt+/+ mice had impaired EB development at three weeks of age, which normalized with adulthood. Together, the data shows that DNM2-dependent Mpl-mediated endocytosis in platelets and MKs is required for steady-state hematopoiesis and provides novel insights into a developmentally controlled role for Mpl in normal erythropoiesis, regulating hemoglobin and heme production.

Combinatorial genetics reveals the Dock1-Rac2 axis as a potential target for the treatment of NPM1;Cohesin mutated AML.

Acute myeloid leukemia (AML) is driven by mutations that occur in numerous combinations. A better understanding of how mutations interact with one another to cause disease is critical to developing targeted therapies. Approximately 50% of patients that harbor a common mutation in NPM1 (NPM1cA) also have a mutation in the cohesin complex. As cohesin and Npm1 are known to regulate gene expression, we sought to determine how cohesin mutation alters the transcriptome in the context of NPM1cA. We utilized inducible Npm1cAflox/+ and core cohesin subunit Smc3flox/+ mice to examine AML development. While Npm1cA/+;Smc3Δ/+ mice developed AML with a similar latency and penetrance as Npm1cA/+ mice, RNA-seq suggests that the Npm1cA/+; Smc3Δ/+ mutational combination uniquely alters the transcriptome. We found that the Rac1/2 nucleotide exchange factor Dock1 was specifically upregulated in Npm1cA/+;Smc3Δ/+ HSPCs. Knockdown of Dock1 resulted in decreased growth and adhesion and increased apoptosis only in Npm1cA/+;Smc3Δ/+ AML. Higher Rac activity was also observed in Npm1cA/+;Smc3Δ/+ vs. Npm1cA/+ AMLs. Importantly, the Dock1/Rac pathway is targetable in Npm1cA/+;Smc3Δ/+ AMLs. Our results suggest that Dock1/Rac represents a potential target for the treatment of patients harboring NPM1cA and cohesin mutations and supports the use of combinatorial genetics to identify novel precision oncology targets.

Reduced Antibodies and Innate Cytokine Changes in SARS-CoV-2 BNT162b2 mRNA Vaccinated Transplant Patients With Hematological Malignancies.

Immunocompromised individuals including patients with hematological malignancies constitute a population at high risk of developing severe disease upon SARS-CoV-2 infection. Protection afforded by vaccination is frequently low and the biology leading to altered vaccine efficacy is not fully understood. A patient cohort who had received bone marrow transplantation or CAR-T cells was studied following a 2-dose BNT162b2 mRNA vaccination and compared to healthy vaccine recipients. Anti-Spike antibody and systemic innate responses were compared in the two vaccine cohorts. The patients had significantly lower SARS-CoV-2 Spike antibodies to the Wuhan strain, with proportional lower cross-recognition of Beta, Delta, and Omicron Spike-RBD proteins. Both cohorts neutralized the wildtype WA1 and Delta but not Omicron. Vaccination elicited an innate cytokine signature featuring IFN-γ, IL-15 and IP-10/CXCL10, but most patients showed a diminished systemic cytokine response. In patients who failed to develop antibodies, the innate systemic response was dominated by IL-8 and MIP-1α with significant attenuation in the IFN-γ, IL-15 and IP-10/CXCL10 signature response. Changes in IFN-γ and IP-10/CXCL10 at priming vaccination and IFN-γ, IL-15, IL-7 and IL-10 upon booster vaccination correlated with the Spike antibody magnitude and were predictive of successful antibody development. Overall, the patients showed heterogeneous adaptive and innate responses with lower humoral and reduced innate cytokine responses to vaccination compared to naïve vaccine recipients. The pattern of responses described offer novel prognostic approaches for potentiating the effectiveness of COVID-19 vaccination in transplant patients with hematological malignancies.

Lumbar Spine Posttherapeutic Imaging.

Management of patients after lumbar spine surgery or interventional radiology can be complex, and postoperative imaging patterns are often poorly understood by nonspecialized radiologists. This article focuses on postoperative imaging features of the lumbar spine in five clinical settings (with corresponding interventions): vertebral osteoporotic fractures (percutaneous vertebroplasty and vertebral augmentation), lumbar disk herniation (surgical diskectomy and percutaneous interventional radiology), lumbar spinal stenosis (surgical decompression), lumbar spondylolisthesis (surgical decompression and fusion), and degenerative scoliosis (techniques of osteotomies).For each intervention, we discuss imaging indications, depending if the patient is asymptomatic or if there are suspected complications, describe normal and pathologic imaging features, and present key points.

Extracellular ST6GAL1 regulates monocyte-macrophage development and survival.

Interaction of immune cells with the systemic environment is necessary for the coordinated development and execution of immune responses. Monocyte-macrophage lineage cells reside at the junction of innate and adaptive immunity. Previously we reported that the sialyltransferase ST6GAL1 in the extracellular milieu modulates B cell development and IgG production, granulocyte production, and attenuates acute airway inflammation to bacterial challenge in mouse models. Here, we report that extracellular ST6GAL1 also elicits profound responses in monocyte-macrophage lineage cells. We show that recombinant ST6GAL1 adheres to subsets of thioglycolate-elicited inflammatory cells in the mouse peritoneum and to cultured human monocyte THP-1 cells. Exposure of the inflammatory cells to recombinant ST6GAL1 elicited wholesale changes in the gene expression profile of primary mouse myeloid cells; most notable was the striking up-regulation of monocyte-macrophage and monocyte-derived dendritic cell development pathway signature genes and transcription factors PU.1, NFκB and their target genes, driving increased monocyte-macrophage population and survival ex vivo. In the cultured human monocyte cells, the essential cell surface receptor of the monocyte-macrophage lineage, the M-CSF receptor (M-CSF-R, Csfr1) was a target of extracellular ST6GAL1 catalytic activity. Extracellular ST6GAL1 activated the M-CSF-R and initiated intracellular signaling events, namely, the nuclear translocation of NFκB subunit p65, and phosphorylation of ERK 1/2 and AKT. The findings implicate extracellular ST6GAL1 in monocyte development by a mechanism initiated at the cell surface and support an emerging paradigm of an extracellular glycan-modifying enzyme as a central regulator coordinating immune hematopoietic cell development and function.

[Giant-cell tumor of bone in 2022]. / La tumeur à cellules géantes des os en 2022.

Giant cell tumors of bone (GCTs) are rare mesenchymal tumors classified as intermediate in the WHO 2020 classification, i.e. neither completely benign nor definitely malignant, due to recurrence (frequent) and pulmonary metastases (rare). They involve the end of long bones as well as the axial bones of mature skeletons. They are made of mononuclear stromal tumor cells of (pre-) osteoblastic phenotype, mononuclear cells of the monocyte-macrophage lineage and osteoclast-like multinuclear giant cells responsible for tumor osteolysis. In 95% of cases, the stromal cells have a specific mutation in the H3F3A gene which encodes histone H3.3. The mutated H3.3 G34W protein (90% of cases) can be easily detected by immunohistochemistry, even on small samples. Many tumors or bone pseudotumors contain osteoclast-like giant cells, cells of the bone microenvironment, and should not be confused with GCT: mainly brown tumor of hyperparathyroidism, aneurysmal bone cyst, chondroblastoma, non-ossifying fibroma and central giant cell granuloma.

Spinal anesthesia for open gastrostomy in an infant after stage I Norwood for hypoplastic left heart.

Infants with hypoplastic left heart are at increased risk of adverse events including mortality when they undergo procedures with general anesthesia in the inter-stage period after stage I Norwood. This is primarily caused by an imbalance between pulmonary and systemic blood flows augmented by decreased function of the single ventricle. These factors can be aggravated by general anesthesia, hence the increased risk. Many of these infants experience feeding dysfunction and require a gastrostomy to optimize nutrition. We report a case of open gastrostomy in an infant with Norwood physiology under spinal anesthesia with an excellent outcome.

Methods to Analyze the Developmental Trajectory of Human Primary NK Cells Using Monocle and SCENIC Analyses.

Development of novel cellular therapies based on primary human NK cells is under active investigation. Human NK cells are comprised of distinct subsets with high transcriptomic heterogeneity. Unique methodologies are being developed to determine the transcriptomic profiles of human NK cells. NK cells account for 10-20% of total lymphocytes in the human peripheral blood, which mediates anti-tumor and anti-viral effector functions. Therapeutic success in the clinic depends on a better understanding of the single-cell transcriptome of human NK cell subsets. Moreover, a better understanding of the transcriptional network that regulates NK cell development, subset specification, and terminal maturation is obligatory for their in vitro generation and expansion toward clinical utilization. Here, we describe the procedure for single-cell RNA-sequencing of human NK cells and strategies for bioinformatic analyses. This protocol provides a data analysis roadmap for investigators who work on the basic biology and therapeutic applications of human NK cells.

CT-Guided Percutaneous Vertebroplasty for Vertebral Non-union Following Posterior Fixation: A Preliminary Retrospective Study.

PURPOSE: Traumatic thoracolumbar vertebral fractures are frequently treated with posterior fixation (PF) and vertebral augmentation. Sometimes, it is deemed too risky to offer vertebral augmentation under fluoroscopic guidance alone. Adjuvant CT/fluoroscopy-guided percutaneous vertebroplasty (PVP) could be offered in certain scenarios. The aim was to evaluate feasibility, safety and effectiveness of PVP in patients presenting with vertebral non-union (VNU) following PF performed without concomitant vertebral augmentation. MATERIALS AND METHODS: All patients treated in our institution with PVP between July 2015 and July 2020 were retrospectively reviewed. Patients treated with CT/fluoroscopy-guided PVP under local anesthesia for symptomatic VNU following PF were selected. Three criteria were established to assess cement distribution, considering vertebral filling of: (1) fracture cleft, (2) anterior two-thirds of the vertebral body, (3) from superior to inferior endplates. Numeric pain rating scale (NPRS) assessing grade of discomfort (0 = no pain; 10 = worst pain) and complications were evaluated before and 1 month after PVP. RESULTS: Ten patients were identified (mean age 53 ± 12y). Mean time between PF and PVP was 9.6 [2-35] months. Two patients required further cement injection with a second PVP. Eight patients had satisfactory vertebral filling according to the three criteria. Mean NPRS reduction was 2.7(-42%, p < 0.05). No significant complications occurred. CONCLUSIONS: Combined CT/fluoroscopy guidance seems a useful tool to perform PVP in VNU following PF, even in presence of orthopedic metalwork. Interventional radiologists may help in these scenarios, performing an adjuvant PVP under local anesthesia. In this small series, the procedure seems safe and effective and could be taken in consideration as alternative to revision surgery.

Differential roles of BAF and PBAF subunits, Arid1b and Arid2, in MLL-AF9 leukemogenesis.

The Switch/Sugar Non-Fermenting (SWI/SNF) nucleosome remodeling complexes play important roles in normal development and in the development of various cancers. Core subunits of the SWI/SNF complexes have been shown to have oncogenic roles in acute myeloid leukemia. However, the roles of the unique targeting subunits, including that of Arid2 and Arid1b, in AML leukemogenesis are not well understood. Here, we used conditional knockout mouse models to elucidate their role in MLL-AF9 leukemogenesis. We uncovered that Arid2 has dual roles; enhancing leukemogenesis when deleted during leukemia initiation and yet is required during leukemia maintenance. Whereas, deleting Arid1b in either phase promotes leukemogenesis. Our integrated analyses of transcriptomics and genomic binding data showed that, globally, Arid2 and Arid1b regulate largely distinct sets of genes at different disease stages, respectively, and in comparison, to each other. Amongst the most highly dysregulated transcription factors upon their loss, Arid2 and Arid1b converged on the regulation of Etv4/Etv5, albeit in an opposing manner while also regulating distinct TFs including Gata2,Tcf4, Six4, Irf4 and Hmgn3. Our data demonstrate the differential roles of SWI/SNF subunits in AML leukemogenesis and emphasize that cellular context and disease stage are key in determining their functions during this process.

Optimization of whole-body 2-[18F]FDG-PET/MRI imaging protocol for the initial staging of patients with myeloma.

OBJECTIVE: To determine the optimal 2-[18F]FDG-PET/MRI imaging protocol for the initial staging of patients with suspected or confirmed multiple myeloma. METHODS: Radiologists and nuclear medicine specialists reviewed all PET/MRI exams of 104 patients with a monoclonal gammopathy (MG). The presence of focal and diffuse bone marrow involvement (BMI) was assessed using 4 different image datasets: WB-MRI, PET, WB-PET/MRI, and WB-DCE-PET/MRI. A reference standard was established by a panel review of all baseline and follow-up imaging, and biological and pathological information. The diagnostic performance for each image dataset to detect BMI was evaluated and compared (Fisher's exact test). RESULTS: Sensitivity, specificity, and accuracy for focal BMI of WB-MRI was 87%, 97%, and 92%; of PET was 78%, 97%, and 95%; of WB-PET/MRI was 93%, 97%, and 95%; and of WB-DCE-PET/MRI was 93%, 97%, and 95%, respectively. WB-PET/MRI and WB-DCE-PET/MRI were statistically superior to PET (p = 0.036) without decreasing specificity. The sensitivity, specificity, and accuracy of WB-MRI for diffuse BMI detection was 91%, 80%, and 85%; of 3DT1-PET was 53%, 89%, and 74%; of WB-PET/MRI was 98%, 66%, and 79%; and of WB-DCE-PET/MRI was 98%, 59%, and 75%, respectively. PET lacked sensitivity compared to all other dataset studies (p < 0.0001). WB-MRI had the best accuracy without reaching statistical significance when compared to the other datasets. CONCLUSION: The WB-PET/MRI dataset including T1 and T2 Dixon, WB-DWI, and PET images provides optimal diagnostic performance to detect both focal lesions and diffuse BMI, with limited added value of WB-DCE for baseline staging of patients with MG. Key Points • The combination of morphological and functional MRI sequences and metabolic (2-[18F]FDG-PET) images increases the diagnostic performance of PET/MRI to detect focal bone lesions. • The adjunction of dynamic contrast-enhanced sequences did not improve diagnostic performance.

Immune cells surveil aberrantly sialylated O-glycans on megakaryocytes to regulate platelet count.

Immune thrombocytopenia (ITP) is a platelet disorder. Pediatric and adult ITP have been associated with sialic acid alterations, but the pathophysiology of ITP remains elusive, and ITP is often a diagnosis of exclusion. Our analysis of pediatric ITP plasma samples showed increased anti-Thomsen-Friedenreich antigen (TF antigen) antibody representation, suggesting increased exposure of the typically sialylated and cryptic TF antigen in these patients. The O-glycan sialyltransferase St3gal1 adds sialic acid specifically on the TF antigen. To understand if TF antigen exposure associates with thrombocytopenia, we generated a mouse model with targeted deletion of St3gal1 in megakaryocytes (MK) (St3gal1MK-/-). TF antigen exposure was restricted to MKs and resulted in thrombocytopenia. Deletion of Jak3 in St3gal1MK-/- mice normalized platelet counts implicating involvement of immune cells. Interferon-producing Siglec H-positive bone marrow (BM) immune cells engaged with O-glycan sialic acid moieties to regulate type I interferon secretion and platelet release (thrombopoiesis), as evidenced by partially normalized platelet count following inhibition of interferon and Siglec H receptors. Single-cell RNA-sequencing determined that TF antigen exposure by MKs primed St3gal1MK-/- BM immune cells to release type I interferon. Single-cell RNA-sequencing further revealed a new population of immune cells with a plasmacytoid dendritic cell-like signature and concomitant upregulation of the immunoglobulin rearrangement gene transcripts Igkc and Ighm, suggesting additional immune regulatory mechanisms. Thus, aberrant TF antigen moieties, often found in pathological conditions, regulate immune cells and thrombopoiesis in the BM, leading to reduced platelet count.