Von Willebrand Factor-cleaving Protease Research Articles

The effect of ADAMTS13 on graft-versus-host disease.

Allogeneic haematopoietic stem cell transplantation (allo-HSCT) can potentially cure malignant blood disorders and benign conditions such as haemoglobinopathies and immunologic diseases. However, allo-HSCT is associated with significant complications. The most common and debilitating among them is graft-versus-host disease (GVHD). In GVHD, donor-derived T cells mount an alloimmune response against the recipient. The alloimmune response involves several steps, including recognition of recipient antigens, activation and proliferation of T cells in secondary lymphoid organs, and homing into GVHD-targeted organs. Adhesion molecules on T cells and endothelial cells mediate homing of T cells into lymphoid and non-lymphoid tissues. In this study, we showed that Von Willebrand factor (VWF), an adhesion molecule secreted by activated endothelial cells, plays an important role in mouse models of GVHD. We investigated the effect of the VWF-cleaving protease ADAMTS13 on GVHD. We found that ADAMTS13 reduced the severity of GVHD after bone marrow transplantation from C57BL6 donor to BALB/C recipient mice. A recombinant VWF-A2 domain peptide also reduced GVHD in mice. We showed that ADAMTS13 and recombinant VWF-A2 reduced the binding of T cells to endothelial cells and VWF invitro, and reduced the number of T cells in lymph nodes, Peyer's patches and GVHD-targeted organs invivo. We identified LFA-1 (αLβ2) as the binding site of VWF on T cells. Our results showed that blocking T-cell homing by ADAMTS13 or VWF-A2 peptide reduced the severity of the GVHD after allo-HSCT, a potentially novel method for treating and preventing GVHD.

Plasmapheresis combined with rituximab treatment of a case of thrombotic thrombocytopenic purpura with Sjögren syndrome and renal impairment: A case report.

Thrombotic thrombocytopenic purpura (TTP) is a rare thrombotic microangiopathy caused by reduced activity of the von Willebrand factor-cleaving protease (ADAMTS13), which can be life-threatening. The patient reported in this case study also had concurrent Sjögren syndrome and renal impairment, presenting multiple symptoms and posing a great challenge in treatment. A 25-year-old woman in the postpartum period visited the hospital due to indifference in consciousness for more than 1 day following cesarean section 8 days prior. Notable decreases were observed in platelets, hemoglobin, creatinine, and ADAMTS13 levels. After a consultative examination by an ophthalmologist, she was diagnosed with retinal hemorrhage in the right eye and dry eye syndrome in both eyes. Having been diagnosed with TTP with Sjögren syndrome and renal impairment, she received repeated treatments with plasmapheresis combined with rituximab. Following treatment and during the follow-up period, the patient's platelet counts and bleeding symptoms significantly improved. TTP has a high mortality rate, and when combined with Sjögren syndrome and renal impairment, it poses an even greater challenge in treatment. However, after administering standard plasmapheresis combined with rituximab treatment, the treatment outcome is favorable.

Overview of ADAMTS13 Protein in Diagnosis and Patient Management of TTP

The accurate diagnosis and effective management of Thrombotic Thrombocytopenic Purpura (TTP), a rare but life-threatening hematologic disorder, rely critically on the assessment of ADAMTS13 activity. ADAMTS13, a von Willebrand factor-cleaving protease, plays a pivotal role in the pathophysiology of TTP. This review synthesizes current understanding and recent advancements in the role of ADAMTS13 in the diagnosis and therapeutic monitoring of TTP, with a specific focus on the implementation of a fluorescence resonance energy transfer (FRET)-based assay for ADAMTS13 activity. Our retrospective analysis of 50 suspected TTP cases, including 19 confirmed diagnoses, revealed that the FRET-based assay significantly improved the sensitivity and specificity of TTP diagnosis compared to traditional qualitative methods. Furthermore, the FRET assay facilitated timely initiation of appropriate therapies and monitoring of disease activity, underscoring its utility in clinical practice. Our findings highlight the FRET-based ADAMTS13 activity assay's contribution to enhancing the diagnostic accuracy and management efficiency of TTP, suggesting its potential as a standard diagnostic tool in clinical settings. The review aims to provide a comprehensive overview for hematologists and laboratory medicine practitioners, encouraging the adoption of the FRET-based assay to improve patient outcomes in TTP management.

Comparison of thrombomodulin, vWF, and ADAMTS13 levels between preeclampsia and normal pregnancy

To determine and compare plasma thrombomodulin, von Willebrand factor and von Willebrand factorcleaving protease levels between pre-eclamptic and healthy pregnant females. The cross-sectional, comparative study was conducted at the Department of Haematology, University of Health Sciences, Lahore, Pakistan, from November 2019 to December 2020, and comprised pregnant females who were divided into healthy pregnant group A and pre-eclamptic group B. Plasma thrombomodulin and von Willebrand factor-cleaving protease levels were determined by using commercially available enzyme-linked immunosorbent assay kit, and von Willebrand factor level was determined by using immuno-turbidimetric assay kit. Data was analysed using SPSS 25. Of the 88 participants, there were 44(50%) females with mean age 25.5±6 years in group A and 44(50%) in group B with mean age 26±5 years. Median thrombomodulin level in group B was significantly higher than group A (p=0.003). Median von Willebrand factor-cleaving protease levels were lower in group B compared to group A (p=0.838). A significant difference in von Willebrand factor level was observed between the groups (p=0.038). Females with pre-eclampsia had significantly higher plasma levels of von Willebrand factor and thrombomodulin than healthy pregnant subjects.

Von Willebrand factor processing in patients with advanced chronic liver disease and its relation to portal hypertension and clinical outcome

Background and aimsEndothelial dysfunction and portal hypertension (PH) are reflected by increased von Willebrand factor antigen (VWF-Ag) levels in advanced chronic liver disease (ACLD). This study investigated VWF release and cleavage and their association with PH and clinical outcomes.MethodsLevels of VWF-Ag, VWF-N (VWF-propeptide), and VWF-A (VWF processed by the main VWF-cleaving protease ADAMTS13) were assessed in 229 patients with clinically stable ACLD (hepatic venous pressure gradient [HVPG] ≥ 6 mmHg; absence of bacterial infections or acute decompensation) undergoing HVPG-measurement. Liver-healthy individuals served as controls (n = 24).ResultsVWF-Ag and VWF-N were similarly accurate for the identification of clinically significant PH (CSPH; HVPG ≥ 10 mmHg) in compensated ACLD (AUROC: VWF-Ag 0.748; VWF-N 0.728). ADAMTS13 activity was similar between patients with ACLD and controls and did not correlate with PH and disease severity, whereas VWF cleavage decreased in patients with CSPH (i.e., VWF-Ag/-A-ratio increased). In vitro VWF activity strongly reflected VWF-Ag levels (Spearman’s r = 0.874, p < 0.001), but decreased (vs. controls) in patients with CSPH when normalized to VWF-Ag levels (VWF-activity/-Ag-ratio). VWF-Act/-Ag ratio correlated negatively with ADAMTS13 activity (r =– 0.256, p < 0.001). ADAMTS13 activity was independently predictive for (i) portal vein thrombosis (PVT) and (ii) hepatic decompensation or liver-related death.ConclusionsVWF-Ag levels and its propeptide are similarly suitable surrogates of PH in patients with compensated ACLD. ADAMTS13-Act was not linked to disease and PH severity, however, when normalized to VWF-Ag, both VWF cleavage and VWF activity were decreased in patients with CSPH, as compared to liver-healthy individuals. Low ADAMTS13-Act was associated with presumably more procoagulant VWF and adverse outcomes.Clinical trial numberNCT03267615

Endothelial VWF is critical for the pathogenesis of vaso-occlusive episode in a mouse model of sickle cell disease

Vaso-occlusive episode (VOE) is a common and critical complication of sickle cell disease (SCD). Its pathogenesis is incompletely understood. von Willebrand factor (VWF), a multimeric plasma hemostatic protein synthesized and secreted by endothelial cells and platelets, is increased during a VOE. However, whether and how VWF contributes to the pathogenesis of VOE is not fully understood. In this study, we found increased VWF levels during tumor necrosis factor (TNF)-induced VOE in a humanized mouse model of SCD. Deletion of endothelial VWF decreased hemolysis, vascular occlusion, and organ damage caused by TNF-induced VOE in SCD mice. Moreover, administering ADAMTS13, the VWF-cleaving plasma protease, reduced plasma VWF levels, decreased inflammation and vaso-occlusion, and alleviated organ damage during VOE. These data suggest that promoting VWF cleavage via ADAMTS13 may be an effective treatment for reducing hemolysis, inflammation, and vaso-occlusion during VOE.

Clinical characteristics and outcome of 69 patients with thrombotic thrombocytopenic purpura

To analyze the clinical characteristics, diagnosis, treatment and outcome of patients with thrombotic thrombocytopenic purpura (TTP). The clinical data of 69 adult patients with TTP were retrospectively analyzed. There were 19 males and 50 females with a median age of 42 (18-79) years. PLASMIC score 6-7 was recognized in 82.8% (53/64) patients. The activity of von Willebrand factor-cleaving protease (ADAMTS13), which was detected in 21 patients before treatment, was less than 5% in 17 patients and 5%-10% in 3 patients. All 69 patients were treated with plasma exchange (PEX) and/or fresh frozen plasma infusion (PI), 43 of whom were also given glucocorticoid. In addition to PEX/PI and glucocorticoid, rituximab and/or immunosuppressants were administrated in 20 patients. The median follow-up time was 12 (1-57) months. The remission rate was 69.6%, while the relapse rate was 11.6%. The 2-year overall survival (OS) rate was 69.6%±5.5%. The univariate and multivariate analysis showed that relapsed/refractory disease was an independent risk factor for OS. The 2-year OS rate of relapsed/refractory patients was significantly lower than that of the rest patients (41.5%±9.8% vs. 83.7%±5.6%, P<0.001). Regarding the unfavorable prognosis in relapsed/refractory patients, rituximab and/or immunosuppressants are strongly recommended for sake of improving the overall survival.

Plasma Proteomics of COVID-19–Associated Cardiovascular Complications: Implications for Pathophysiology and Therapeutics

To gain insights into the mechanisms driving cardiovascular complications in COVID-19, we performed a case-control plasma proteomics study in COVID-19 patients. Our results identify the senescence-associated secretory phenotype, a marker of biological aging, as the dominant process associated with disease severity and cardiac involvement. FSTL3, an indicator of senescence-promoting Activin/TGFβ signaling, and ADAMTS13, the von Willebrand Factor-cleaving protease whose loss-of-function causes microvascular thrombosis, were among the proteins most strongly associated with myocardial stress and injury. Findings were validated in alarger COVID-19 patient cohort and the hamster COVID-19 model, providing new insights into the pathophysiology of COVID-19 cardiovascular complications with therapeutic implications.

175 Upshaw-schulman syndrome in a pregnant woman at a hospital in the amazon region: Case report

Introduction: Upshaw-Schulman Syndrome (USS) is a severe hereditary autoimmune deficiency of a von Willebrand Factor Cleaving Protease (VWF-CP) called ADAMTS 13. Clinical signs are generally mild during childhood, usually with isolated thrombocytopenia. But their symptoms become more evident when patients have infections or become pregnant. It can complicate pregnancy due to a rare but life-threatening disease called thrombotic thrombocytopenic purpura (PTT). Objectives: To report the case of Upshaw-Schulman syndrome in a pregnant woman seen at a hospital in the Amazon region, demonstrating the importance of the correct and early diagnosis to indicate the best therapeutic approach.

Congenital thrombotic thrombocytopenic purpura simulating alloimmune thrombocytopenia

Congenital thrombotic thrombocytopenic purpura (cTTP) is a thrombotic microangiopathic caused by severely reduced activity of the von Willebrand factor-cleaving protease A Disintegrin And Metalloproteinase with a Thrombospondin type 1 Motif, member 13 (ADAMTS-13), which leads to small-vessel platelet-rich thrombi, thrombocytopenia, and microangiopathic hemolytic anemia (MHA) in the absence of neutralizing antibodies. We describe a case of cTTP in a female neonate presenting initially on the 1st day of life with asymptomatic thrombocytopenia thought to be alloimmune thrombocytopenia, then progressed to severe neonatal jaundice, pallor, and MHA, in whom ADAMTS-13 levels <5%, and the anti-ADAMTS-13 antibody titer was negative confirming the diagnosis of cTTP. The patient initially received intravenous immunoglobulin infusion before documenting MHA. She received fresh frozen plasma infusions which successfully reversed the MHA (by supplying ADAMTS-13) and prevented organ damage in this patient.

The Intriguing Relationships of von Willebrand Factor, ADAMTS13 and Cardiac Disease.

von Willebrand factor (VWF) is an adhesive protein involved in primary hemostasis and facilitates platelet adhesion to sites of vascular injury, thereby promoting thrombus formation. VWF exists in plasma as multimers of increasing size, with the largest (high molecular weight; HMW) expressing the greatest functional activity. A deficiency of VWF is associated with a bleeding disorder called von Willebrand disease (VWD), whereas an excess of VWF, in particular the HMW forms, is associated with thrombosis. ADAMTS13 (a disintegrin and metalloproteinase with thrombospondin type 1 motif-13), also known as VWF-cleaving protease, functions to moderate the activity of VWF by cleaving multimers of VWF and limiting the expression of the largest multimers of VWF. A deficiency of ADAMTS13 is therefore associated with an excess of (HMW forms of) VWF, and thus thrombosis. Indeed, any disturbance of the VWF/ADAMTS13 ratio or ‘axis’ may be associated with pathophysiological processes, including prothrombotic tendency. However, both thrombosis or bleeding may be associated with such disturbances, depending on the presenting events. This review evaluates the relationship of VWF and ADAMTS13 with cardiac disease, including cardiac failure, and associated pathophysiology.

Increased VWF and Decreased ADAMTS-13 in COVID-19: Creating a Milieu for (Micro)Thrombosis.

von Willebrand factor (VWF) is a large adhesive multimeric protein involved in hemostasis. The larger the size (or number of VWF multimers), the greater the functionality of the protein. A deficiency or defect of VWF can lead to von Willebrand disease (VWD) and cause bleeding. Conversely, an increase in VWF may create an environment that promotes thrombosis. ADAMS-13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13), sometimes called VWF-cleaving protease, is primarily responsible for controlling the size of VWF. The most severe deficiency (<10% of normal levels) of ADAMTS-13 arises in thrombotic thrombocytopenic purpura, a condition characterized by the presence of ultralarge VWF and clinically resulting in enhanced risk of thrombosis. However, ADAMTS-13 deficiency may result from other pathological processes. Of relevance is the recent finding that COVID-19 (coronavirus disease 2019) is associated with both increased levels and activity of VWF as well as generally decreased (or occasionally normal) activity levels of ADAMTS-13. Thus, in COVID-19 there is an alteration in the VWF/ADAMTS-13 axis, most often described by increased VWF/ADAMTS-13 ratio (or reduced ADAMTS-13/VWF ratio). COVID-19 is also associated with high prothrombotic risk. Thus, the imbalance of VWF and ADAMTS-13 in COVID-19 may be providing a milieu that promotes (micro)thrombosis, in a clinical picture resembling a secondary thrombotic microangiopathy in some patients. This review therefore assesses the literature on VWF, ADAMTS-13, and COVID-19. Whenever reported in COVID-19, VWF has always been identified as raised (compared with normal reference ranges or control populations). Reports have included VWF level (i.e., VWF antigen) and in some cases one or more VWF "activity" (e.g., collagen binding; platelet glycoprotein Ib [GPIb] binding, using ristocetin cofactor or more modern versions including VWF:GPIbR [recombinant] and VWF:GPIbM [mutant]). Whenever reported, ADAMTS-13 has been reported as "normal" or reduced; however, it should be recognized that "normal" levels may still identify a relative reduction in individual cases. Some reports also discuss the raised VWF/ADAMTS-13 (or reduced ADAMTS-13/VWF) ratio, but very few provide actual numerical data.

Treatment strategy for patients with thrombotic thrombocytopenic purpura

Thrombotic thrombocytopenic purpura (TTP) is a rare and potentially life-threatening disease that is characterized by microangiopathic hemolytic anemia, consumptive thrombocytopenia, and ischemic organ damage resulting from the formation of platelet-rich thrombi in the microvasculature. It is especially related to a severe deficiency of ADAMTS13, the specific von Willebrand factor-cleaving protease. Thus, <10% of the normal activity of ADAMTS13 is an essential diagnostic marker for establishing a diagnosis of TTP. TTP can be of congenital form that is termed the Upshaw-Schulman syndrome (USS) that is caused by genetic abnormality of ADAMTS13 and acquired form that is caused by autoantibodies against ADAMTS13. The congenital form is treated with the infusion of fresh frozen plasma, and the treatment of the acquired form involves plasma exchange combined with immunosuppressive therapy that uses corticosteroids and rituximab. Recently, the efficacy and safety of new drugs caplacizumab, single-domain antibody against ADAMTS13, and recombinant ADAMTS13 products have been reported in large-scale clinical trials conducted in other countries. These results suggested the better outcome in the treatment for the patients with TTP in the near future.

Successful treatment of refractory thrombotic thrombocytopenic purpura with cyclosporine; a case report

Thrombotic thrombocytopenic purpura (TTP) is a rare and fetal disease of the blood coagulation system. The treatment of choice for TTP is plasma exchange. There are some different medical remedies for refractory cases with their own complications. The following case is the report of a refractory TTP, who responded to cyclosporine as a newer way of medical treatment. A 42-year-old woman with systemic lupus erythematosus (SLE) was admitted because of hypermenorrhea, hematuria and purpura. She was involved with acute renal failure, fever and seizure in the course of her admission. Fragmented RBC was detected in the peripheral blood smear. Lactate dehydrogenase (LDH) raised up to 1500 U/L. ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13) level was reduced and von Willebrand factor-cleaving protease (ADAMTS13) antibodies were elevated significantly. She was undergone plasma exchange in order to manage TTP. Additionally, she received methylprednisolone for the treatment of TTP. Despite initial response to plasma exchange and methylprednisolone, the patient did not improve. She received cyclosporine for the treatment of refractory TTP. Her clinical and laboratory abnormalities improved significantly with cyclosporine and this response was durable. We concluded that cyclosporine can be an effective treatment in refractory TTP and SLE.

Shear Stress-Induced Activation of von Willebrand Factor and Cardiovascular Pathology.

The von Willebrand factor (vWF) is a plasma protein that mediates platelet adhesion and leukocyte recruitment to vascular injury sites and carries coagulation factor VIII, a building block of the intrinsic pathway of coagulation. The presence of ultra-large multimers of vWF in the bloodstream is associated with spontaneous thrombosis, whereas its deficiency leads to bleeding. In cardiovascular pathology, the progression of the heart valve disease results in vWF deficiency and cryptogenic gastrointestinal bleeding. The association between higher plasma levels of vWF and thrombotic complications of coronary artery disease was described. Of note, it is not the plasma levels that are crucial for vWF hemostatic activity, but vWF activation, triggered by a rise in shear rates. vWF becomes highly reactive with platelets upon unfolding into a stretched conformation, at shear rates above the critical value (more than 5000 s−1), which might occur at sites of arterial stenosis and injury. The activation of vWF and its counterbalance by ADAMTS-13, the vWF-cleaving protease, might contribute to complications of cardiovascular diseases. In this review, we discuss vWF involvement in complications of cardiovascular diseases and possible diagnostic and treatment approaches.

Microvascular dysfunction in COVID-19: the MYSTIC study

RationalePre-clinical and autopsy studies have fueled the hypothesis that a dysregulated vascular endothelium might play a central role in the pathogenesis of ARDS and multi-organ failure in COVID-19.ObjectivesTo comprehensively characterize and quantify microvascular alterations in patients with COVID-19.MethodsHospitalized adult patients with moderate-to-severe or critical COVID-19 (n = 23) were enrolled non-consecutively in this prospective, observational, cross-sectional, multi-center study. Fifteen healthy volunteers served as controls. All participants underwent intravital microscopy by sidestream dark field imaging to quantify vascular density, red blood cell velocity (VRBC), and glycocalyx dimensions (perfused boundary region, PBR) in sublingual microvessels. Circulating levels of endothelial and glycocalyx-associated markers were measured by multiplex proximity extension assay and enzyme-linked immunosorbent assay.Measurements and main resultsCOVID-19 patients showed an up to 90% reduction in vascular density, almost exclusively limited to small capillaries (diameter 4–6 µm), and also significant reductions of VRBC. Especially, patients on mechanical ventilation showed severe glycocalyx damage as indicated by higher PBR values (i.e., thinner glycocalyx) and increased blood levels of shed glycocalyx constituents. Several markers of endothelial dysfunction were increased and correlated with disease severity in COVID-19. PBR (AUC 0.75, p = 0.01), ADAMTS13 (von Willebrand factor-cleaving protease; AUC 0.74, p = 0.02), and vascular endothelial growth factor A (VEGF-A; AUC 0.73, p = 0.04) showed the best discriminatory ability to predict 60-day in-hospital mortality.ConclusionsOur data clearly show severe alterations of the microcirculation and the endothelial glycocalyx in patients with COVID-19. Future therapeutic approaches should consider the importance of systemic vascular involvement in COVID-19.

Optimization of the detection of inhibitory autoantibodies against the VWF-cleaving protease ADAMTS13 with an automated chemiluminescent ADAMTS13 activity immunoassay.

Acquired thrombotic thrombocytopenic purpura is a rare disease associated with the production of autoantibodies against the VWF-cleaving protease ADAMTS13. The detection of these antibodies is made difficult by the instability of ADAMTS13 in citrated plasma and the time-consuming ADAMTS13 assays. The aim of our study was to evaluate the optimal conditions for detecting anti-ADAMTS13 inhibitory antibodies with the novel automated chemiluminescent immunoassay HemosILR AcuStar ADAMTS13 Activity assay. The parallelism between the AcuStar ADAMTS13 calibration curve and ADAMTS13 concentrations in serially diluted citrated plasma was evaluated after 2hours incubation at 25°C, 37°C, or 37°C after addition of Ca2+ to preserve the activity of the metalloprotease. Using Bethesda assays based on the 3 incubation procedures and the HemosILR AcuStar ADAMTS13 Activity assay, the inhibitor titers were determined in patients' samples with ADAMTS13 antibodies and compared with those determined using the TechnozymR ADAMTS13 activity ELISA. The criterion of parallelism was respected for the 3 incubation methods over the range of ADAMTS13 concentrations relevant for the detection of ADAMTS13 inhibitor antibodies in a Bethesda assay. In agreement with this observation, all the incubation methods permitted the accurate detection and quantification of inhibitory anti-ADAMTS13 antibodies in the samples from patients with acquired thrombotic thrombocytopenic purpura. Incubation of plasma samples with normal plasma at 25°C, 37°C, or 37°C after addition of Ca2+ can be used in a Bethesda assay for quantifying the inhibitory activity of antibodies interfering with ADAMTS13 in the chemiluminescent HemosILR AcuStar ADAMTS13 Activity assay.

Clinical analysis of 61 patients with thrombotic thrombocytopenic purpura

OBJECTIVE To analyze and summarize the clinical features, diagnosis, treatment and prognosis of 61 patients with thrombotic thrombocytopenic purpura (TTP), so as to improve the ability of diagnosis and treatment. METHODS The clinical data of 61 TTP patients admitted to Peking University People's Hospital from January 2004 to March 2019 were retrospectively analyzed, and the clinical manifestations, blood routine, hemolysis indicators, and von Willebrand factor lyase (von Willebrand factor-cleaving protease, vWF-CP, also known as ADAMTS13) of these patients were observed. According to the outcome at the time of discharge, they were divided into survival group and death group, and the differences in clinical characteristics, neutrophil to lymphocyte ratio (NLR) and plasma exchange between the two groups were compared. The PLASMIC scores were calculated and compared with ADAMTS13 to determine the accuracy of the PLASMIC score in predicting ADAMTS13. RESULTS Among the 61 TTP patients, 22 were males and 39 were females, with an average age of (48±17) years. In the study, 48 cases had pentalogy, only 9 had triad, and the remaining 4 had no neuropsychiatric symptoms. Twenty-seven cases (44.3%) died and 34 cases (55.7%) survived. Among the 61 TTP patients, the platelet count was (12.9±9.5)×109/L, the hemoglobin (66.5±20.7) g/L, the percentage of erythrocyte fragments 3% (2%, 7%), and the plasma free hemoglobin increased to 360 (200, 457) mg /L, and the lactate dehydrogenase 1 508 (811, 2 133.8) U/L. The blood clotting was basically normal. The ADAMTS13 value of 30 patients was 49.0 (40.8, 61.3) μg/L, the ADAMTS activity of 10 patients was 0.05). The total amount and frequency of plasma exchange (PEX) in the death group were significantly less than those in the survival group, and the difference was statistically significant (P 0.05). CONCLUSION PEX can significantly improve the survival rate of TTP patients. PLASMIC score can easily and quickly predict the possibility of ADAMTS13 activity reduction, which is beneficial to the early diagnosis of TTP and PEX treatment. NLR can reflect the systemic inflammatory process, but its significance in TTP needs further study.

Anti-idiotypic network involved in restoring ADAMTS13 activity in immune-mediated thrombotic thrombocytopenic purpura (iTTP)

Abstract The culprit of iTTP, a fatal autoimmune disease is a severe deficiency of the von Willebrand factor-cleaving protease ADAMTS13, caused by autoantibodies inhibiting its enzymatic activity. The pathophysiology upholding remission in certain patients but leading to relapse in others is unknown. We hypothesize that one mechanism keeping pathogenic autoantibodies in check is a network of anti-idiotypic antibodies, which we aimed to identify and characterize. From splenic mononuclear cells of two frequently relapsing iTTP patients (A and C), the anti-idiotypic IgG1 Fab κ/λ repertoire was amplified by phage display technology on previously generated selecting monoclonal anti-ADAMTS13 Fabs (Schaller et al., Blood 2014). Purified Fabs were pooled (pools A (n=4) and C (n=4)) and each pool was tested for its ability to neutralize anti-ADAMTS13 antibodies thereby restoring ADAMTS13 activity in plasma of 22 iTTP patients using the FRETS-vWF73 assay. Single anti-idiotypic clones revealed a highly diverse IGHV gene usage within and between the two iTTP patients, but four IGHV genes were shared among them. Partial neutralization of functional ADAMTS13 inhibitors of &amp;gt;2BU/ml in 3/11 (27%) and 5/11 (45%) patients and full neutralization in 2/11 (18%) and 3/11 (27%) patients with lower inhibitor titer (1–2BU/ml) were shown for pools A and C, respectively. To summarize, we have identified functional anti-ADAMTS13 anti-idiotypes in the splenic IgG repertoire of two patients underlining the role of an anti-idiotypic response involved in remission of iTTP. The contribution of single anti-idiotypic Fabs to the neutralization potential and plasma mixing studies investigating acute and remission phase antibody repertoires are underway.

Clinical characteristics of 83 patients with thrombotic thrombocytopenic purpura

目的分析血栓性血小板减少性紫癜（TTP）患者的临床特征、治疗方案及转归。方法回顾性分析1998年5月至2019年5月83例TTP患者的临床资料。结果83例TTP患者中，男27例、女56例，中位年龄39（10～68）岁。41例（49.4％）表现为五联征，79例（95.2％）表现为三联征。78.0％（46/59）患者PLASMIC评分≥6分。10例行TTP基因检测，5例TTP基因突变。10例在血浆置换（PEX）前行血管性血友病因子裂解蛋白酶（ADAMTS13）活性检测，9例ADAMTS13活性<10％。83例患者均接受PEX/血浆输注（PI）+糖皮质激素治疗，其中35例联合利妥昔单抗和（或）免疫抑制剂。中位随访34（1～167）个月，总体有效率为81.9％，缓解率为63.9％，复发率为（35.7±7.1）％，3年总生存（OS）率为（78.6±4.6）％。单用PEX/PI+糖皮质激素组有效率（72.9％对94.3％，P＝0.019）、OS率［（63.8±7.5）％对（94.3±3.9）％，χ2＝8.450，P＝0.004］低于联合利妥昔单抗和（或）免疫抑制剂组。多因素COX分析显示高龄（HR＝1.111，95％ CI 1.044～1.184，P＝0.001）、高ALT/AST比值（HR＝1.353，95％ CI 1.072～1.708，P＝0.011）是影响OS的独立危险因素。结论TTP患者多以三联征起病，可伴ADAMTS13活性下降。PEX/PI+糖皮质激素联合利妥昔单抗和（或）免疫抑制剂治疗可提高OS率。高龄和高ALT/AST比值患者预后欠佳。