To cite this article: Ré ti M, Farkas P, Csuka D, Rá zsó K, Schlammadinger Á , Udvardy ML, Madá ch K, Domjá n G, Bereczki C, Reusz GS, Szabó AJ, Prohá szka Z. Complement activation in thrombotic thrombocytopenic purpura. J Thromb Haemost 2012; 10: 791-8.Summary. Background: Ultra-large von Willebrand factor and deficiency of its cleaving protease are important factors in the events leading to thrombotic microangiopathy; however, the mechanisms involved are only partly understood. Whereas pathological activation of the alternative complement pathway is linked to atypical hemolytic uremic syndrome, the role of complement activation in thrombotic thrombocytopenic purpura (TTP) is unknown. The aim of this study was to investigate whether signs of complement activation are characteristic of TTP. Patients and methods: Twenty-three patients with TTP (18 women, median age 38 years) and 17 healthy controls (13 women, median age 38 years) were included. Complement parameters (C3, Factors H, I, B and total alternative pathway activity) together with complement activation fragments (C3a) or complexes (C1rs-INH, C3bBbP, sC5b9) were measured by ELISA or RID. ADAMTS13 activity and anti-ADAMTS13 inhibitory antibodies were measured by the VWF-FRET73 assay. Results: Increased levels of C3a, and SC5b9 were observed in TTP during acute episodes, as compared with healthy controls. Decreased complement C3 levels indicative of complement consumption occurred in 15% of acute TTP patients. Significant decrease of complement activation products C3a and SC5b9 was observed during plasma exchange (PEX). The sustained presence of anti-ADAMTS13 inhibitory antibodies in complete remission was associated with increased complement activation. Conclusion: These data document in an observational study the presence of complement activation in TTP. Further investigation is needed to determine its potential pathogenetic significance.
Acquired factor XIII (FXIII) deficiency due to autoantibody against FXIII is a very rare severe hemorrhagic diathesis. Antibodies directed against the A subunit of FXIII, which interfere with different functions of FXIII, have been described. Here, for the first time, we report an autoantibody against the B subunit of FXIII (FXIII-B) that caused lifethreatening bleeding in a patient with systemic lupus erythematosus. FXIII activity, FXIII-A 2 B 2 complex, and individual FXIII subunits were undetectable in the plasma, whereas platelet FXIII activity and antigen were normal. Neither FXIII activation nor its activity was inhibited by the antibody, which bound to structural epitope(s) on both free and complexed FXIII-B. The autoantibody highly accelerated the elimination of FXIII from the circulation. FXIII supplementation combined with immunosuppressive therapy, plasmapheresis, immunoglobulin, and anti-CD20 treatment resulted in the patient's recovery. FXIII levels returned to around 20% at discharge and after gradual increase the levels stabilized above 50%. IntroductionBlood coagulation factor XIII (FXIII) is a protransglutaminase of tetrameric structure (FXIII-A 2 B 2 ). 1,2 Its potentially active A subunit (FXIII-A) is synthesized in cells of bone marrow origin; it is also present in platelets and monocytes/macrophages in dimeric form (FXIII-A 2 ). The noncatalytic B subunit (FXIII-B) is in excess and it is essential for the stabilization of FXIII-A 2 in plasmatic conditions. FXIII is converted into an active transglutaminase (FXIIIa) by limited proteolysis of FXIII-A and by Ca 2ϩ -induced dissociation of FXIII-B. Cross-linking of fibrin ␣-and ␥-chains and ␣ 2 -plasmin inhibitor to fibrin by FXIIIa stabilizes fibrin and protects it from prompt elimination by plasmin. 3 Inherited FXIII-A deficiency is a severe bleeding diathesis with the high risk of intracranial bleeding in nonsupplemented patients. 4 Only 5 cases of inherited FXIII-B deficiency with mild-to-moderate bleeding tendency have been reported. [5][6][7][8] In the absence of FXIII-B, plasma FXIII activity and FXIII-A concentration were considerably decreased, whereas in platelets a normal amount of FXIII-A was measured. 9 Thirty-six cases of severe FXIII deficiency due to an autoantibody against FXIII-A have been reported. In a few cases, the autoantibody was characterized and classified into subgroups according to its inhibition of FXIII activation, FXIIIa activity, or binding to fibrin. [10][11][12][13][14][15] In about one third of the cases the autoantibody was associated with systemic lupus erythematosus (SLE). No report on an autoantibody directed against FXIII-B has been published so far. MethodsA 28-year-old woman suffering from SLE with end-stage kidney disease was on hemodialysis. For preparation of cubital fistula she was admitted to a county hospital. In the proximity of the surgical wound, hematomas developed that were explored. The wounds showed no tendency of healing and remained open. A few days later extensive intramuscular hematoma ...
SummaryVon Willebrand’s disease (vWD) is the most common congenital haemorrhagic diathesis, characterized by the quantitative or qualitative disorder of von Willebrand factor (vWF). A number of methods have been used for the diagnosis of the disease, and the bleeding time determination is widely accepted as a screening test in spite of its low sensitivity. Our aim was to evaluate and compare the performance of two high shear systems (the O’Brien filter test and the PFA-100 device) in the screening and diagnosis of vWD. Thirty patients (n=13 type 1 with mild symptoms, n = 9 type 1 with severe symptoms, n = 2 type 2A, n = 3 type 2B and n = 3 type 3 vWD) and twenty controls were investigated. In mild vWD the platelet retention in the second phase of the filter test with citrated blood showed the highest sensitivity (91.6%). The sensitivity of the PFA-100 method with collagen-epinephrine cartridges in this group was 76.9%, while the bleeding time was prolonged only in 15.4% of the cases. In severe type 1, in type 2A and type 3 all functional tests reflected the bleeding tendency of the patients. In type 2B disease the bleeding time was prolonged only when the patient was thrombocytopenic, but both high shear systems revealed the disease independently of the presence of thrombocytopenia. The overall sensitivity of the bleeding time determination was 50% compared to the 80-90% sensitivity of the O’Brien filter test and the PFA-100 system. The sensitivity values of the filter test and the PFA-100 device with collagen-epinephrine cartridges were in the same range, but the collagen-ADP cartridges showed a lower (65.5%) sensitivity, though the results were specific and had high positive predictive value. We conclude that both high shear systems are suitable for the screening of vWD, and that they are superior to the traditional bleeding time determination in case of mild disease or type 2B vWD.
Background von Willebrand disease Vicenza is characterized by low plasma VWF levels, the presence of ultra-large (UL) VWF multimers and less prominent satellite bands on multimer gels, and the heterozygous amino acid substitution R1205H in the VWF gene. The pathogenesis of VWD Vicenza has been elusive. Accelerated clearance is implicated as a cause of low VWF level. Objectives We addressed the question, whether the presence of ultra-large multimers is a cause, or a result of accelerated VWF clearance, or whether it is an unrelated phenomenon. Patients/Methods We studied the detailed phenotype of three Hungarian patients with VWD Vicenza, expressed the mutant VWF-R1205H in 293T cells, and developed a mathematical model to simulate VWF synthesis and catabolism. Results We found that the half life of VWF after DDAVP was approximately one tenth of that after the administration of Haemate P, a source of exogenous wild type VWF (0.81±0.2 vs. 7.25±2.38 hours). An analysis of recombinant mutant VWF-R1205H showed that the biosynthesis and multimer structure of WT and mutant VWF were indistinguishable. A mathematical model of the complex interplay of VWF synthesis, clearance and cleavage showed that decreasing VWF half life to one tenth of normal reproduced all features of VWD Vicenza including low VWF level, ultra-large multimers and a decrease of satellite band intensity. Conclusion We conclude that accelerated clearance alone may explain all features of VWD Vicenza.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.