T1 - Sensitization of CD4+ T cells to coagulation factor VIII


Also in the case of the von Willebrand-Syndrome a hereditary factor VIII-deficiency may be observed. Acquired deficiencies (disorders in synthesis and turnover) are rare. The formation of factor VIII inhibitors is more frequently observed; especially after substitution therapy in patients with Haemophilia A. Formation of inhibitors may also be caused by autoimmune diseases, drug treatments (e.g. penicillin) and in monoclonal granulopathies and lymphoproliferative diseases. As acute-phase-protein factor VIII may be increased postoperatively, in phase I of a DIC, in liver diseases, tumor diseases, inflammation, and vascular disease, as well as after physical and mental stress situations (blood sampling).

Factor VIII: structure and function in blood clotting.

T1 - Human CD4+ T-cell epitope repertoire on the C2 domain of coagulation factor VIII

Coagulation Factor VIII Is Synthesized In Endothelial Cells

Factor VIII (FVIII) and factor V (FV) are homologous coagulation cofactors sharing a similar domain organization (A1-A2-B-A3-C1-C2) and are both extensively glycosylated within their B-domains. In mammalian cell expression systems, compared with FV, the FVIII primary translation product is inefficiently transported out of the endoplasmic reticulum. Here we show that FVIII is degraded within the cell by a lactacystin-inhibitable pathway, implicating the cytosolic 20 S proteasome machinery. Protein chaperones calnexin (CNX) and calreticulin (CRT) preferentially interact with glycoproteins containing monoglucosylated N-linked oligosaccharides and are proposed to traffic proteins through degradative and/or secretory pathways. Utilizing co-immunoprecipitation assays, intracellular FVIII was detected in association with CNX maximally within 30 min to 1 h following synthesis, whereas FV could not be detected in association with CNX. In contrast, both FVIII and FV displayed interaction with CRT during transit through the secretory pathway. B-domain deleted FVIII significantly reduced the CNX and CRT interaction, indicating the B-domain may represent a primary CNX and CRT interaction site. In the presence of inhibitors of glucose trimming, the interactions of FVIII with CNX, and of FVIII and FV with CRT, were significantly reduced whereas the secretion of FVIII, and not FV, was inhibited. In addition, transfection in a glucosidase I-deficient Chinese hamster ovary cell line (Lec23) demonstrated that both degradation and secretion of FVIII were inhibited, with little effect on the secretion of FV. These results support that CNX and CRT binding, mediated at least in part by the B-domain of FVIII, is required for efficient FVIII degradation and secretion. In contrast, FV does not require CNX interaction for efficient secretion. The results suggest a unique requirement for carbohydrate processing and molecular chaperone interactions that may limit the productive secretion of FVIII.

Factor VIII (FVIII, anti-hemophilic factor, ..

Factor VIII is present in plasma in complex with von Willebrand-factor. The glycoprotein is related to factor V with respect to primary structure (40% identity) as well as cofactor-function in the plasmatic coagulation. After the activation by thrombin factor VIIIa forms together with factor IXa, phospholipids and calcium ions the tenase complex, which is responsible for the activation of factor X. As factor V, factor VIII is also inactivated by activated Protein C through proteolytic cleavage.

Therefore, activation of Factor X can be thought of as the point at which the extrinsic and intrinsic pathways of coagulation ultimately converge.

Expression of Recombinant Human Coagulation Factor …

Bleeding tendency is the manifestation of a wide range of abnormalities that can basically classify into two major categories according to etiology; these are the inherited and acquired categories. The pathologic defect resides in one of the three major sequential physiologic processes of blood homeostasis. Defects in coagulation include mainly inherited defect in the synthesis of one of the members of factors of coagulation such as factor VIII (Hemophilia A) and factor IX (Hemophilia B) and to a much less extent factor XI (Hemophilia C). The current study aimed to explore the oral health status in a sample of hemophilia male children. The present case control study included 22 children with hemophilia disorders and 50 apparently healthy aged matched control children. The age of hemophilia children ranged from 2-14 years. Dmft and DMFT were assessed and the results showed that patients had significantly higher scores indicating poor oral hygiene.

used for the synthesis of erythropoietin, factor VIII, ..

AB - Factor VIII (FVIII) and factor V (FV) are homologous coagulation cofactors sharing a similar domain organization (A1-A2-B-A3-C1-C2) and are both extensively glycosylated within their B-domains. In mammalian cell expression systems, compared with FV, the FVIII primary translation product is inefficiently transported out of the endoplasmic reticulum. Here we show that FVIII is degraded within the cell by a lactacystin-inhibitable pathway, implicating the cytosolic 20 S proteasome machinery. Protein chaperones calnexin (CNX) and calreticulin (CRT) preferentially interact with glycoproteins containing monoglucosylated N-linked oligosaccharides and are proposed to traffic proteins through degradative and/or secretory pathways. Utilizing co-immunoprecipitation assays, intracellular FVIII was detected in association with CNX maximally within 30 min to 1 h following synthesis, whereas FV could not be detected in association with CNX. In contrast, both FVIII and FV displayed interaction with CRT during transit through the secretory pathway. B-domain deleted FVIII significantly reduced the CNX and CRT interaction, indicating the B-domain may represent a primary CNX and CRT interaction site. In the presence of inhibitors of glucose trimming, the interactions of FVIII with CNX, and of FVIII and FV with CRT, were significantly reduced whereas the secretion of FVIII, and not FV, was inhibited. In addition, transfection in a glucosidase I-deficient Chinese hamster ovary cell line (Lec23) demonstrated that both degradation and secretion of FVIII were inhibited, with little effect on the secretion of FV. These results support that CNX and CRT binding, mediated at least in part by the B-domain of FVIII, is required for efficient FVIII degradation and secretion. In contrast, FV does not require CNX interaction for efficient secretion. The results suggest a unique requirement for carbohydrate processing and molecular chaperone interactions that may limit the productive secretion of FVIII.

The hepatic synthesis of four coagulation factors, Factor II ..

It should be pointed out that activation of Factor X by Factor IX is enhanced by Factor VIII and the presence of phospholipid complexes provided by activated platelets (See ).