PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “ADAMTS13 Protein”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 199 records · Page 11Linked to original sources
PubMed2006

[A case of thrombotic thrombocytopenic purpura with systemic lupus erythematosus].

We described a case of thrombotic thrombocytopenic purpura (TTP) with systemic lupus erythematosus (SLE). A-60-year old woman was admitted to our hospital because of fever, disconsciousness, and general fatigue. 32 years ago, she was diagnosed as SLE with Raynaud's phenomenon, rash, photosensitivity, arthritis, lymphocytopenia, and ANA. Her SLE was well controlled with 10 mg predonisolone as a maintance dose until several weeks ago. On admission, severe thrombocytopenia (0.7x10(4)/microl) and other laboratory data revealed microangiopathic hemolytic anemia and renal dysfunction, Immediately after diagnosed as TTP, plasma exchange and corticosteroid therapy started. In spite of the treatment, disconsciousness progressed and systemic convulsion occurred and died 4 days after admission. Autopsied examination revealed diffuse microvascular hyalinized thrombi in heart, kidney, liver, spleen, and pancreas. Some microvascular thrombi were detected in lymph nodes, bone marrow, intestine. Pathological diagnosis of TTP was made on microvascular hyalinized platelet thrombi in organs. Von Willebrand factor-cleaving protease (VWF-CP) activity in plasma on set is less than 0.5 percent of normal and inhibitor for VWF-CP was detected. We here report a valuable case for analysis of pathogenesis in SLE-TTP.

ADAM Proteins↗
PubMed2007

Acquired ADAMTS-13 deficiency in pediatric patients with severe sepsis.

We studied the state of ultra-large von Willebrand factor (ULVWF) proteolysis in 21 pediatric patients with severe sepsis and found that the overall group of patients had moderately reduced ADAMTS-13 activity, but 31% had severe enzymatic deficiency. The severe deficiency correlated with greater adhesion activity of von Willebrand factor, severity of thrombocytopenia and plasma levels of interleukin-6. It also correlated clinically with severity of illness and organ dysfunction. These results suggest that ULVWF proteolysis is insufficient in septic patients and severely deficient in a subgroup of patients. The deficiency may contribute to the development of thrombocytopenia and ischemic organ failure associated with sepsis.

ADAM Proteins↗
PubMed2003

Posttransplantation thrombotic thrombocytopenic purpura: a single-center experience and a contemporary review.

OBJECTIVE: To assess the activity of von Willebrand factor-cleaving protease (vWF-CP) in patients with thrombotic thrombocytopenic purpura (TTP) complicating bone marrow transplantation (BMT) and peripheral blood stem cell transplantation (PBSCT). PATIENTS AND METHODS: From March 1, 1999, to June 30, 2001, allogeneic and autologous hematopoietic stem cell transplantation was performed in 118 and 400 patients, respectively. We reviewed risk factors for development of posttransplantation TTP and measured vWF-CP activity during active TTP in 10 recipients. RESULTS: The incidence of TTP after allogeneic and autologous transplantation was 6.8% (8/118) and 0.25% (1/400), respectively. Among the allogeneic transplant recipients, the incidence of TTP after nonmyeloablative (NMA) PBSCT, matched unrelated donor BMT, and sibling BMT or PBSCT was 15.4% (2/13), 11.8% (2/17), and 4.5% (4/88), respectively. Of the 10 patients with TTP, 9 (90%) had received extensive prior therapy, including autologous transplantation in both NMA recipients. Acute graft-vs-host disease (GVHD) prophylaxis consisted of cyclosporine and methotrexate in most affected patients. The vWF antigen level was elevated in all patients, and no patients showed evidence of vWF-CP deficiency. During active TTP, 6 patients had grade II-IV acute GVHD, 1 had extensive chronic GVHD, and 4 had cytomegalovirus viremia. Risk factor analysis for development of TTP showed that transplant type (NMA and matched unrelated donor) and source of stem cells (bone marrow vs peripheral blood stem cell) were significant. CONCLUSIONS: Posttransplantation TTP was not found to be associated with severe vWF-CP deficiency. The elevated levels of vWF antigen are consistent with diffuse endothelial injury likely because of multiple interacting factors such as extensive prior therapy, GVHD, cyclosporine, and reactivation of cytomegalovirus. The disorder appears to be more frequent among patients with, or at risk for, acute GVHD, suggesting a possible role in the pathogenesis. Nonmyeloablative transplantation does not appear to confer a lesser risk, possibly for these reasons.

ADAM Proteins↗
PubMed2003

Von Willebrand factor-cleaving protease (ADAMTS-13) activity in thrombotic microangiopathies: diagnostic experience 2001/2002 of a single research laboratory.

BACKGROUND: Severe deficiency of von Willebrand factor-cleaving protease (ADAMTS-13) activity (<5% of normal) is specific for classical thrombotic thrombocytopenic purpura (TTP), a disorder presenting with thrombocytopenia, microangiopathic haemolytic anaemia and often with organ dysfunction such as neurological symptoms, renal failure, and fever. A certain, though according to several case series, variable percentage of patients with clinically diagnosed TTP and most patients with other forms of thrombotic icroangiopathies (TMA) do not show severe ADAMTS-13 deficiency. METHODS: We determined ADAMTS-13 activity in 508 plasma samples of 309 patients referred to our laboratory in 2001 and 2002. Plasma samples with ADAMTS-13 activity <5% were additionally tested for the presence of inhibitory antibodies. Patients were assigned to ten predefined clinical categories according to information provided in the referral letter (TMA not specified; TMA associated with neoplasia or chemotherapy; TMA following haematopoietic stem cell transplantation; TMA with additional disorder; idiopathic TTP; haemolytic-uraemic syndrome (HUS) not specified; HUS with diarrhoea prodrome; atypical HUS; other haematological disorder; no clinical information available). RESULTS: We detected 50 (16%) patients with severe ADAMTS-13 deficiency. Forty-four (88%) of these patients had been classified as idiopathic TTP, 2 as neoplasia- or chemotherapy-associated, and 4 as non-specified TMA. Among the patients labelled as acute idiopathic TTP, the prevalence of severe ADAMTS-13 deficiency was 63% (44/70). Inhibitory antibodies were found in 31 (62%) patients with ADAMTS-13 activity <5%. Of the 44 patients with acute idiopathic TTP, at initial presentation or at relapse, with ADAMTS-13 activity <5%, 11 were identified to have (probable) constitutional severe ADAMTS-13 deficiency. CONCLUSION: Severe ADAMTS-13 deficiency is found in about 60% of patients diagnosed with idiopathic TTP but in none of 111 diagnosed with HUS. Plasma ADAMTS-13 activity <5%, however, does not identify all patients clinically diagnosed with TTP. Detection of inhibitory antibodies against ADAMTS-13 helps to differentiate between acquired and constitutional forms of TTP, which may be important for treatment strategies.

ADAM Proteins↗
PubMed1999

Thrombotic thrombocytopenic purpura and autoimmunity: a tale of shadows and suspects.

BACKGROUND AND OBJECTIVE: The key pathogenic feature of TTP is the formation of platelet aggregates within the microcirculation; however, the etiology of such aggregates has been elusive for years. A large amount of evidence points to an abnormal interaction between damaged vascular endothelium and platelets, although the cause of the primary microvascular endothelial cell injury is seldom clear. The autoimmune hypothesis often recurs, and this is based on a number of observations: the claimed superiority of plasma-exchange over plasma infusion, the anecdotal report of the presence of immunocomplexes and autoantibodies in TTP patients, the efficacy of the administration of corticosteroids and other immunosuppressant agents, and the concomitant occurrence of TTP in association with autoimmune diseases, especially systemic lupus erythematosus (SLE). This review will focus on the complex relationships between TTP and humoral autoimmunity; in particular, similarities and differences between TTP, SLE and antiphospholipid (aPL) antibodies syndrome, as well as the putative role of several other antibodies directed towards endothelial cells and/or platelets, including the recently discovered anti-CD36 antibodies and antivWF-cleaving metalloprotease, will be discussed. DESIGN AND METHODS: The authors have been involved in the study and treatment of TTP and autoimmune diseases for years; furthermore, the PubMed data base of the National Library of Congress has been extensively searched using the Internet. CONCLUSIONS: Although over the years evidence has increased in favor of the autoimmune hypothesis for TTP etiopathogenesis, TTP should not yet be considered an autoimmune disease. Autoantibodies should be regarded as only one of the many different insults which can trigger microvascular thrombosis even though the autoimmune theory of the pathogenesis of TTP is gaining more and more strength. As far as concerns the relationship between TTP, SLE and aPL antibodies-related disorders, these diseases should be distinguished on the basis of both different clinical presentations and accurate antibody screening, although this approach should definitely not delay the prompt start of treatment.

ADAM Proteins↗
PubMed1999

Deficient activity of von Willebrand's factor-cleaving protease in patients with disseminated malignancies.

An aberrant platelet immunorelated glycoprotein Ib (GPIb) receptor expressed by human tumor cells appears to participate in primary adhesive interactions required for the metastatic process. Hence, we questioned whether plasma von Willebrand's factor (vWf), its adhesive ligand, manifested comparable anomalies in patients with disseminated tumors. Plasma specimens from patients with disseminated metastases showed 68% (P < 0.013), 91% (P < 0.0009), and 207% (P < 0.0009) enhancements in FVIII:C activity, vWf-related antigen levels, and ristocetin co-factor activity, respectively, whereas their SDS-agarose electrophoretic analysis demonstrated a 165% (P < 0.001) increase in the highly polymeric forms of vWf compared to control preparations from patients with corresponding, localized solid tumors. Substantially reduced levels of vWf-cleaving protease activity were observed in study patient specimens, with no plasma inhibitors detectable. The clinical presence and absence of tumor metastases correlated significantly with vWf-cleaving enzyme activities of < or = 15% and > or = 88%, respectively (n = 20; P < 0.0001). Finally, with an in vitro model system, tumor-induced platelet aggregation was enhanced by 127% (P < 0.001) in study patient platelet-rich plasma (PRP) compared to control PRP and could be completely inhibited (P < 0.0009) when both tumor cells and their PRP substrates were incubated with monoclonal antibodies directed against the vWf binding epitope of GPIb alpha and against the GPIb binding epitope of plasma vWf, respectively. Unusually large vWf multimers observed in patients with disseminated tumors probably result from deficient vWf-cleaving protease activity and may represent a novel mechanism regulating primary platelet-tumor adhesive interactions involved in the metastatic process.

ADAM Proteins↗
PubMed1999

Recovery and half-life of von Willebrand factor-cleaving protease after plasma therapy in patients with thrombotic thrombocytopenic purpura.

Plasma exchange using fresh-frozen plasma (FFP) for replacement was given to two brothers during a relapse of thrombotic thrombocytopenic purpura (TTP). A constitutional deficiency of von Willebrand factor(vWF)-cleaving protease had been previously established in both patients. No inhibitor of vWF-cleaving protease was present in patients' plasmas. They received plasma exchange for four and three consecutive days, respectively. In both patients, the activity of vWF-cleaving protease after the first plasmapheresis session was evaluated and was found to be virtually identical to anticipated activity calculated from predicted patient plasma volume and volume of exchanged plasma. Pathologic platelet counts and lactate dehydrogenase levels were normalized in both patients within 4-6 days. The biologic half-life of vWF-cleaving protease was determined in these patients following the last plasma exchange. The respective half-lives of 3.3 and 2.1 days represent the lowest known clearance rates of proteases in circulating human plasma. Another patient with relapsing TTP was treated with plasma exchange and/or plasma infusion for 10 consecutive days during the first relapse, 221-231 days after the initial TTP event. Pharmacokinetic studies of vWF-cleaving protease were performed after plasma exchange on day 221 and after plasma infusion on day 231. High level of an IgG in patient plasma, capable of completely inhibiting protease activity in an equal volume of normal plasma, had been established prior to first plasmapheresis. There was no measurable protease activity at any time during plasma therapy. Following plasma exchange, the level of the inhibitor was transiently slightly depressed. After 10 days of plasma therapy, the concentration of the inhibitor in patient plasma was increased about 5-fold. We suggest that, in contrast to protease deficient patients without circulating inhibitor, complementary therapy including immunosuppressive treatment, vincristine and/or splenectomy is indicated in patients with acquired inhibitors of vWF-cleaving protease. Testing for vWF-cleaving protease inhibitor may be useful in predicting the response to plasma exchange in patients with TTP.

ADAM Proteins↗
PubMed1999

Estimation of the von Willebrand factor-cleaving protease in plasma using monoclonal antibodies to vWF.

A protease present in plasma cleaves von Willebrand factor (vWF) at the peptide bond 842Tyr-843Met of the mature subunit. To quantify this vWF-cleaving protease activity in plasma we have developed a simple method based on the estimation by IRMA of the degradation of a constant amount of wild type recombinant vWF used as substrate, by serial dilutions of test plasma used as protease provider. vWFAg was estimated by two-site IRMA using as first coating antibody a monoclonal antibody (MoAb) whose epitope is localized on the C-terminal side of the cleavage site, and as second labeled antibody a pool of MoAbs specific for the N-terminal side. Because the proteolytic process leads to the progressive separation of the C- and N-terminal portions of the vWF subunit such an IRMA also shows a progressive apparent loss of vWFAg. In contrast, the levels of vWFAg estimated after proteolysis by regular IRMA remained essentially constant. Results obtained with this new method were compared with the analysis by SDS-agarose gel electrophoresis of the multimeric pattern of proteolyzed WT-rvWF and no significant difference was noted testing a series of 28 plasmas. As compared with normal pooled plasma, 14 normal individuals and 13 patients with various types of vWD had normal levels of protease activity (44-178%) by both methods. The validity of the method was confirmed by showing a lack of detectable protease activity in a patient with chronic relapsing thrombotic thrombocytopenic purpura. In conclusion our method appears as a useful tool for the quantification of the vWF-cleaving protease activity in plasma. Its sensitivity and specificity are similar to those of SDS-gel electrophoresis. However, this new IRMA has the major advantages of being much simpler and faster, and open to most research laboratories in the field.

ADAM Proteins↗
PubMed1999

Assay of von Willebrand factor (vWF)-cleaving protease based on decreased collagen binding affinity of degraded vWF: a tool for the diagnosis of thrombotic thrombocytopenic purpura (TTP)

Patients with thrombotic thrombocytopenic purpura (TTP) have a deficiency of von Willebrand factor (vWF)-cleaving protease, whereas patients with hemolytic-uremic syndrome (HUS) show normal activity of this protease. Present methods for assaying vWF-cleaving protease by immunoblotting are time-intensive and cumbersome. We therefore developed a new functional assay based on the preferential binding of high-molecular-weight forms of vWF to collagen. In this assay, the diluted plasma sample to be tested is added to normal human plasma in which protease activity had been abolished. The vWF present in the protease-depleted plasma is digested by the vWF-cleaving protease in the test plasma. The proteolytic degradation leads to low-molecular-weight forms of vWF, which show impaired binding to microtiter plates coated with human collagen type III. The collagen-bound vWF is quantified using a peroxidase-conjugated rabbit antibody against human vWF. The values of vWF-cleaving protease activity in tested plasma samples are read from a calibration curve achieved by incubating the vWF-substrate with dilutions of a normal human plasma pool (NHP). Testing of plasma from patients with TTP and HUS showed that the assay can be used to distinguish between these two syndromes. The presence of an inhibitor can be detected by carrying out the test after incubation of NHP with the patient plasma sample, thus enabling differentiation of patients with familial TTP from those with nonfamilial TTP.

ADAM Proteins↗