Antibodies against Noncatalytic B Subunit of Factor XIII Inhibit Activation of Factor XIII and Fibrin Crosslinking

BACKGROUND

 Coagulation factor XIII (FXIII) is a proenzyme of plasma transglutaminase. It comprises two catalytic A subunits (FXIII-A) and two carrier B subunits (FXIII-B). We previously reported that alloantibodies against FXIII-B could promote FXIII clearance in a patient with congenital FXIII-B deficiency who had received infusions of plasma-derived human FXIII (A2B2 heterotetramer).

OBJECTIVES

 We aimed to investigate whether anti-FXIII-B antibodies affect the catalytic function of FXIII.

METHODS

 FXIII activation and fibrin crosslinking were examined in the presence of patient plasma, isolated patient IgG, or rat anti-FXIII-B monoclonal antibodies.

RESULTS

 Alloantibody levels were increased by repeated infusions of plasma-derived A2B2 heterotetramer, which enhanced binding to the functionally important FXIII-B sushi domains. The patient plasma strongly inhibited cleavage of the FXIII-A activation peptide, amine incorporation, and fibrin crosslinking in normal plasma. Furthermore, anti-FXIII-B alloantibodies blocked the formation of the complex of FXIII-B with FXIII-A, and fibrinogen. Rat monoclonal antibodies against the 10th sushi domain of FXIII-B inhibited the incorporation of FXIII-B to fibrin, FXIII activation (i.e., cleavage of FXIII-A activation peptide), and ultimately fibrin crosslinking in normal plasma, independent of their effect on heterotetramer assembly with FXIII-A. Alloantibody binding to the A2B2 heterotetramer blocked the access of thrombin to the FXIII-A cleavage site, as indicated by the reaction of the alloantibodies to the A2B2 heterotetramer and FXIII-B, but not to FXIII-A.

CONCLUSION

 Anti-FXIII-B antibodies binding to the A2B2 heterotetramer and FXIII-B inhibited FXIII activation and its crosslinking function despite being directed against its noncatalytic subunit (FXIII-B).

Management of autoimmune factor XIII deficiency in a frail, elderly patient

Autoimmune factor XIII/13 deficiency (aFXIII deficiency) is a rare hemorrhagic disorder, for which typical guideline-directed treatment is aggressive immunosuppressive therapy. Approximately 20% of patients are over 80 years old; however, and optimum management of such patients has not reached consensus. Our elderly patient had massive intramuscular hematoma, and aFXIII deficiency was diagnosed. The patient opted against aggressive immunosuppressive therapy, so he was managed with conservative treatment only. Thorough survey of other correctable causes of bleeding and anemia is also required in similar cases. Our patient's serotonin-norepinephrine reuptake inhibitor use and multivitamin deficiency (vitamin C, B 12 and folic acid) were revealed to be aggravating factors. Fall prevention and muscular stress prevention are also important in elderly patients. Our patient had two relapses of bleeding within 6 months, which were improved spontaneously by bed rest without factor XIII replacement therapy or blood transfusion. Conservative management may be preferred for frail and elderly patients with aFXIII deficiency when they opt against standard therapy.

Management of Acquired Factor X Deficiency Caused by In Vitro Non-neutralizing Anti-factor X Autoantibodies with Pre-emptive Corticosteroid Therapy

Coagulation factor X (FX) deficiency causes severe hemorrhagic symptoms. We herein report a 90-year-old man with hemorrhagic symptoms and prolongation of prothrombin time (PT) and activated partial thromboplastin time (APTT). Cross-mixing tests showed a factor deficiency pattern, but administration of plasma products was not effective. Acquired coagulation factor deficiency was suspected, and immunosuppressive therapy was started. After the intervention, his hemorrhagic symptoms improved. A decrease in FX activity was later confirmed, and anti-FX autoantibody was retrospectively detected by an enzyme-linked immunosorbent assay. Immediate intervention is important for patients suspected of having acquired coagulation factor deficiency.

Serum proteomic identification and validation of two novel atherosclerotic aortic aneurysm biomarkers, profilin 1 and complement factor D

BACKGROUND

Effective diagnostic biomarkers for aortic aneurysm (AA) that are detectable in blood tests are required because early detection and rupture risk assessment of AA can provide insights into medical therapy and preventive treatments. However, known biomarkers for AA lack specificity and reliability for clinical diagnosis.

METHODS

We performed proteome analysis of serum samples from patients with atherosclerotic thoracic AA (TAA) and healthy control (HC) subjects to identify diagnostic biomarkers for AA. Serum samples were separated into low-density lipoprotein, high-density lipoprotein, and protein fractions, and the major proteins were depleted. From the proteins identified in the three fractions, we narrowed down biomarker candidates to proteins uniformly altered in all fractions between patients with TAA and HC subjects and evaluated their capability to discriminate patients with TAA and those with abdominal AA (AAA) from HC subjects using receiver operating characteristic (ROC) analysis. For the clinical validation, serum concentrations of biomarker candidates were measured in patients with TAA and AAA registered in the biobank of the same institute, and their capability for the diagnosis was evaluated.

RESULTS

Profilin 1 (PFN1) and complement factor D (CFD) showed the most contrasting profiles in all three fractions between patients with TAA and HC subjects and were selected as biomarker candidates. The PFN1 concentration decreased, whereas the CFD concentration increased in the sera of patients with TAA and AAA when compared with those of HC subjects. The ROC analysis showed that these proteins could discriminate patients with TAA and AAA from HC subjects. In the validation study, these candidates showed significant concentration differences between patients with TAA or AAA and controls. PFN1 and CFD showed sufficient area under the curve (AUC) in the ROC analysis, and their combination further increased the AUC. The serum concentrations of PFN1 and CFD also showed significant differences between patients with aortic dissection and controls in the validation study.

CONCLUSION

PFN1 and CFD are potential diagnostic biomarkers for TAA and AAA and measurable in blood samples; their diagnostic performance can be augmented by their combination. These biomarkers may facilitate the development of diagnostic systems to identify patients with AA.

Critical Roles of the Cysteine-Glutathione Axis in the Production of γ-Glutamyl Peptides in the Nervous System

γ-Glutamyl moiety that is attached to the cysteine (Cys) residue in glutathione (GSH) protects it from peptidase-mediated degradation. The sulfhydryl group of the Cys residue represents most of the functions of GSH, which include electron donation to peroxidases, protection of reactive sulfhydryl in proteins via glutaredoxin, and glutathione conjugation of xenobiotics, whereas Cys-derived sulfur is also a pivotal component of some redox-responsive molecules. The amount of Cys that is available tends to restrict the capacity of GSH synthesis. In in vitro systems, cystine is the major form in the extracellular milieu, and a specific cystine transporter, xCT, is essential for survival in most lines of cells and in many primary cultivated cells as well. A reduction in the supply of Cys causes GPX4 to be inhibited due to insufficient GSH synthesis, which leads to iron-dependent necrotic cell death, ferroptosis. Cells generally cannot take up GSH without the removal of γ-glutamyl moiety by γ-glutamyl transferase (GGT) on the cell surface. Meanwhile, the Cys-GSH axis is essentially common to certain types of cells; primarily, neuronal cells that contain a unique metabolic system for intercellular communication concerning γ-glutamyl peptides. After a general description of metabolic processes concerning the Cys-GSH axis, we provide an overview and discuss the significance of GSH-related compounds in the nervous system.

Novel immunochromatographic test for anti-factor XIII B subunit autoantibodies to diagnose autoimmune acquired factor XIII deficiency

Autoimmune factor XIII (FXIII) deficiency (AiF13D) is an acquired life-threatening bleeding disorder due to anti-FXIII autoantibodies (autoAbs). We previously established an immunochromatographic test (ICT) for detection of anti-FXIII-A subunit (FXIII-A) autoAbs. Conversely, the detection of anti-FXIII-B subunit (FXIII-B) autoAbs is currently performed in a limited number of medical facilities through time-consuming and expensive laboratory tests, such as dot-blotting analysis and enzyme-linked immunosorbent assay (ELISA). Accordingly, in this study, we generated eight rat monoclonal antibodies (mAbs) against human FXIII-B using the rat lymph node method. By employing an ELISA, two mAbs, 2G12B10 and 8H12B9, were selected considering the distance between the recognition regions of each mAb (the 6th and 9th-10th Sushi domain, respectively) and the strength of their reactivity. Using this mAb combination, we prototyped an ICT to detect anti-FXIII-B autoAbs and distinguish between AiF13D and "non-immune" acquired FXIII deficiency (acF13D), and tested it with 22 healthy controls, 23 acF13D patients, 15 AiF13D patients without anti-FXIII-B autoAbs, and 8 AiF13D patients with anti-FXIII-B autoAbs. Receiver operating characteristics curve analyses of ICTs for anti-FXIII-B autoAbs were performed and revealed a precision similar to dot-blot analysis. Human anti-FXIII-A mAbs were also generated from a single patient with AiF13D using a new cDNA cloning method, and their binding properties were characterized. Consequently, anti-FXIII-A IgG preparations were established as potentially permanent positive controls of ICT for anti-FXIII-A antibodies. Combining the previously developed ICT for anti-FXIII-A autoAbs and the novel ICT for anti-FXIII-B autoAbs may reduce false negatives and lead to appropriate diagnosis and treatment.

Epitope analysis of human monoclonal antibodies from a patient with autoimmune factor XIII deficiency reveals their inhibitory mechanisms

Autoimmune coagulation factor XIII (FXIII) deficiency (AiF13D) is a bleeding disorder caused by anti-FXIII autoantibodies. Recently, we generated human monoclonal antibodies (mAbs) from the peripheral blood of an AiF13D patient and classified them into three groups: FXIII-dissociation inhibitor, FXIII-assembly inhibitor, and non-neutralizing/inhibitory mAbs. However, the epitope region and molecular inhibitory mechanism of each mAb remain unknown. Here, we localized the epitope regions of the representative inhibitory mAbs A69K (dissociation inhibitor) and A78L (assembly inhibitor) to the β-barrel-2 domain and boundary of β-barrel-1&2 domains, respectively, of the FXIII-A subunit, by combining a binding assay using its synthesized peptides and a protease-protection assay. Our findings suggest that A69K inhibits the activation-related conformational changes and dissociation of FXIII and that A78L competitively inhibits FXIII-assembly.

Utility of 5-aminolaevulinic acid fluorescence-guided endoscopic biopsy for malignant mesothelioma in a cat and dog

Malignant mesothelioma (MM) is uncommon in cats and dogs and can be challenging to diagnose. Adequate tissue sampling is required for superior diagnostic accuracy. Protoporphyrin IX, a metabolite of 5-aminolaevulinic acid (5-ALA), is a photosensitiser for photodynamic diagnosis (PDD). To the best of our knowledge, no study has reported the use of 5-ALA-PDD to detect MM in veterinary medicine. The present study describes the use of 5-ALA-PDD for MM diagnosis in a cat and dog, as well as the effectiveness of intracavitary chemotherapy. We evaluated the use of PDD with 5-ALA hydrochloride (5-ALA-PDD) in two cases of MM. A 12-year-old cat presented with a 1-month history of respiratory distress, and a 9-year-old dog presented with a 3-month history of mild abdominal distention. We endoscopically biopsied lesions in both the cases using 5-ALA-PDD. Histopathological examination revealed mesothelioma, and immunohistochemical staining was positive for calretinin. Both patients were treated with carboplatin. The cat died of respiratory failure. Although, the dog's condition improved 21 days after the first chemotherapeutic drug administration, the dog died on day 684 owing to cardiac-related issues. 5-ALA-PDD is thus, safe and feasible for the diagnosis of MM in veterinary medicine.

Identification of non-neutralizing anti-factor X autoantibodies in three Japanese cases of autoimmune acquired factor X deficiency

INTRODUCTION

Autoimmune factor X (FX or F10) deficiency (AiF10D) is an extremely rare acquired haemorrhagic disorder characterized by a severe reduction in FX activity due to autoantibodies against FX.

AIM

Anti-FX autoantibodies were investigated in four patients with suspected AiF10D, and their properties were analysed.

METHODS AND RESULTS

Anti-FX auto antibodies in plasma were detected by ELISA with three of four cases. One case of anti-FX autoantibody negativity was later diagnosed as AL-amyloidosis. IgG1 and IgG3 coexisted in all anti-FX autoantibodies of the three patients with AiF10D (cases X1, X2, and X3). Western blot analysis showed that the antibodies were bound to the FX light chain for cases X2 and X3, but the binding was weak for case X1. When the fusion proteins of a secretory luciferase with full-length FX or its γ-carboxylated glutamic acid (Gla) domain were added to the plasma of the three patients, both fusion proteins were immunoprecipitated as antigen-antibody complexes. Contrarily, the latter fusion protein produced in the presence of warfarin demonstrated a decrease in the collection rate, suggesting that their autoantibodies recognized the light chain and regions containing Gla residues. Since all three patients were essentially negative for FX inhibitors, it was concluded that the anti-FX autoantibodies for these cases were predominantly non-neutralizing. The concentration of the FX antigen also significantly reduced in these patients, suggesting that anti-FX autoantibodies promote the clearance of FX.

CONCLUSION

Immunological anti-FX autoantibody detection is highly recommended to ensure that AiF10D cases are not overlooked, and to start necessary immunosuppressive therapies.

Acquired von Willebrand Syndrome in a Patient with Multiple Comorbidities, Including MALT Lymphoma with IgA Monoclonal Gammopathy and Hyperviscosity Syndrome

Acquired von Willebrand syndrome (aVWS) develops with various underlying diseases. We herein report an individual with aVWS associated with mucosa-associated lymphoid tissue lymphoma in the lungs complicated by hyperviscosity syndrome, Sjögren's syndrome, and hypothyroidism. This patient developed life-threatening hemorrhaging during a lung biopsy despite transfusion of concentrate of plasma-derived VWF/factor VIII. The use of rituximab caused remission of the lymphoma and hyperviscosity syndrome in parallel with the resolution of aVWS. Thus, lymphoma and hyperviscosity might result in aVWS. Invasive procedures with a risk of bleeding should be avoided in individuals with aVWS.

Acquired factor V inhibitor with erythema and eosinophilia in a patient with end-stage renal disease

Autoimmune factor V deficiency (AiFVD) is a rare bleeding disorder caused by factor V inhibitors. In this report, we present the case of an 89-year-old man who developed bleeding tendency during surgery to create arteriovenous fistula for hemodialysis. The bleeding tendency developed with prolongation of activated partial thromboplastin and prothrombin time, following drug-induced eruption and eosinophilia. Significant reduction in coagulation factor activity and inhibitory pattern in cross-mixing tests suggested the presence of inhibitors to coagulation factors. Subsequently, we detected a factor V inhibitor and anti-factor V autoantibodies was confirmed using enzyme-linked immunosorbent assay with purified human plasma factor V. Thus, the patient was 'definitely diagnosed' with AiFVD in accordance with the diagnostic criteria enacted by the Japanese Ministry of Health, Labor, and Welfare. The bleeding tendency improved after initiating oral prednisolone 50 mg (1 mg/kg) followed by normalization of activated partial thromboplastin time and prothrombin time at the 34th day. After improving the coagulation system prolongation, the inhibitor and autoantibodies has been eradicated. Since it is suggested that drug-induced immune response can cause AiFVD, AiFVD should be considered in patients who undergo hemodialysis and develop failure of hemostasis and drug-induced eruption.

Cloning of human anti-factor XIII monoclonal antibody dissects mechanisms of polyclonal antibodies in a single patient

BACKGROUND

Coagulation factor XIII (FXIII) consists of 2 A (FXIII-A) and 2 B (FXIII-B) subunits that cross-link and strengthen the hemostatic fibrin thrombus; thus, abnormal bleeding occurs when FXIII is significantly reduced. Autoimmune-acquired FXIII deficiency (AiF13D) is characterized by lethal bleeding secondary to the development of autoantibodies against FXIII. However, since anti-FXIII autoantibodies are polyclonal, the mechanism underlying FXIII dysfunction is unclear.

OBJECTIVES

The objective of this study was to dissect the inhibitory mechanisms of polyclonal anti-FXIII autoantibodies.

METHODS

In this study, we prepared the human monoclonal antibodies (hmAbs) from the peripheral blood of an 86-year-old man with AiF13D by using a new complementary DNA cloning method and analyzed the properties of each autoantibody.

RESULTS

Seventeen clones obtained from hmAbs were divided into the following 3 groups: dissociation inhibitors of FXIII-A₂B₂ (6 clones), assembly inhibitors of FXIII-A₂B₂ (3 clones), and nonneutralizing/inhibitory hmAbs (8 clones). Dissociation inhibitors strongly inhibited fibrin cross-linking and amine incorporation. Assembly inhibitors extracted FXIII-A from FXIII-A₂B₂, strongly inhibited binding of FXIII-A to FXIII-B, and activation peptide cleavage. However, the patient's plasma presented a strong inhibition of A₂B₂ heterodimer assembly but only a slight inhibition of thrombin-Ca²⁺-dependent dissociation, suggesting that the assembly inhibitors concealed the effect of dissociation inhibitors in plasma. By contrast, nonneutralizing antibodies had little effect on the function of FXIII, suggesting that nonneutralizing hmAbs (and/or dissociation inhibitors and/or assembly inhibitors) promoted the clearance of FXIII-A from the blood.

CONCLUSION

Cloning of anti-FXIII autoantibodies enabled us to not only elucidate the mechanism and pathophysiology of AiF13D but also develop a completely new type of anticoagulant.

Involvement of Nitric Oxide in Protecting against Radical Species and Autoregulation of M1-Polarized Macrophages through Metabolic Remodeling

When the expression of NOS2 in M1-polarized macrophages is induced, huge amounts of nitric oxide (•NO) are produced from arginine and molecular oxygen as the substrates. While anti-microbial action is the primary function of M1 macrophages, excessive activation may result in inflammation being aggravated. The reaction of •NO with superoxide produces peroxynitrite, which is highly toxic to cells. Alternatively, however, this reaction eliminates radial electrons and may occasionally alleviate subsequent radical-mediated damage. Reactions of •NO with lipid radicals terminates the radical chain reaction in lipid peroxidation, which leads to the suppression of ferroptosis. •NO is involved in the metabolic remodeling of M1 macrophages. Enzymes in the tricarboxylic acid (TCA) cycle, notably aconitase 2, as well as respiratory chain enzymes, are preferential targets of •NO derivatives. Ornithine, an alternate compound produced from arginine instead of citrulline and •NO, is recruited to synthesize polyamines. Itaconate, which is produced from the remodeled TCA cycle, and polyamines function as defense systems against overresponses of M1 macrophages in a feedback manner. Herein, we overview the protective aspects of •NO against radical species and the autoregulatory systems that are enabled by metabolic remodeling in M9-polarized macrophages.

[Autoimmune coagulation factor V/5 deficiency during chronic disseminated intravascular coagulation]

Aortic regurgitation, a thoracoabdominal aortic aneurysm, chronic myeloid leukemia, and chronic kidney disease were all being treated at two hospitals for an 83-year-old man. He was admitted to the Department of Orthopedics at our hospital with a lumbar compression fracture. Later, he experienced melena, for which the Department of Internal Medicine was consulted. Due to the aberrant results of PT-INR (7.1) and a PTT > 200 seconds on a coagulation test, we suspected the presence of an autoimmune coagulation factor deficiency, and prednisolone immunosuppressive therapy medication was started right away. Due to a sharp decline in FV/5 activity, the presence of FV/5 inhibitors, and the presence of anti-FV/5 autoantibodies, a final diagnosis of autoimmune coagulation factor V (FV/5) deficiency was made. After the start of immunosuppressive therapy, the FV/5 inhibitor and anti-FV/5 autoantibodies disappeared, and the FV/5 activity progressively returned to normal. Disseminated intravascular coagulation-which may have been caused by a known aortic aneurysm-worsened while tapering off prednisolone. Due to the patient's advanced age and other problems, the aneurysm was extensive and inappropriate for surgical repair. The coagulation test findings improved gradually upon initiation of warfarin therapy. Herein, the patient had autoimmune FV/5 deficiency, a rare disorder that made diagnosis and therapy difficult because of the patient's several coexisting conditions.

[Coagulative complete remission following early gastric cancer resection in a patient with steroid-resistant acquired hemophilia A and nephrotic syndrome]

During laparoscopic cholecystectomy, an 89-year-old man was discovered to have a prolonged APTT. He was transferred to our hospital for a thorough examination because wound bleeding necessitated a reoperation. Based on coagulation factor VIII activity (FVIII:C) of 3.6% and FVIII inhibitor levels of 48.5 BU/ml, he was diagnosed with acquired hemophilia A (AHA). Due to concerns about his advanced age and postoperative infection, immunosuppressive therapy with prednisolone 0.5 mg/kg/day was initiated. His clinical course was favorable, except hemorrhagic shock caused by intramuscular hemorrhage on the right back, although low FVIII inhibitor levels persisted for more than a month; additionally, lower leg edema and increased urinary protein were also observed. He was diagnosed as with AHA and secondary nephrotic syndrome, possibly because of early gastric cancer. As a result, radical endoscopic submucosal dissection (ESD) was performed while a recombinant coagulation factor VIIa preparation was administered. AHA improved rapidly following ESD, and coagulative remission was achieved. Simultaneously, the nephrotic syndrome improved. Because the control of malignant tumors may improve the status of AHA, the timing of malignant tumor intervention must be considered considering the risk of bleeding and infection associated with immunosuppression.

A Review of Autoimmune Acquired von Willebrand Factor Deficiency in Japan

von Willebrand factor (VWF) forms high-molecular-weight multimers and plays an essential role in hemostasis, and thus its deficiency leads to bleeding symptoms. Acquired von Willebrand syndrome (AVWS) is rare, but potentially underdiagnosed, and develops in various underlying disorders. AVWS caused by anti-VWF autoantibodies is a rare subcategory of AVWS that can also be referred to as autoimmune VWF deficiency (AiVWFD). We performed a search of patients with autoimmune coagulation factor deficiencies in our nationwide survey in Japan. Among these, suspected cases of AiVWFD were extremely few, with only 11 case consultations in the last 10 years. Of these, three and five were respectively positive for anti-VWF autoantibodies (anti-VWF-Ab) and VWF inhibitor (VWF-inh). We also performed an extensive literature search of other cases from Japan, and in total, 40 cases were finally identified to have AiVWFD, with mean age of 55.0 years. Most underlying disorders were lympho- or myeloproliferative diseases, followed by autoimmune diseases. The major bleeding sites were subcutaneous and mucosal, the bleeding severity was moderate, and there were no hemorrhagic deaths. Bleeding time was prolonged; factor VIII activity, VWF antigen, and VWF activity were decreased, and high-molecular-weight VWF multimers were absent or decreased. These are similar to the common abnormal laboratory findings observed among general AVWS cases. Hemostatic therapy often involved VWF concentrates and vasopressin, and antibody eradication therapy often included corticosteroids and achieved remission. Notably, of all cases, 68% had anti-VWF-Abs, and 83% of anti-VWF-Ab-positive patients were also VWF-inh positive. To accumulate precise clinical information on AiVWFD, it is necessary to verify and improve the measurement methods for both anti-VWF-Ab and anti-VWF-inh. These findings from Japan should be confirmed in other geographic localities.

Endothelial Natriuretic Peptide Receptor 1 Play Crucial Role for Acute and Chronic Blood Pressure Regulation by Atrial Natriuretic Peptide

BACKGROUND

ANP (atrial natriuretic peptide), acting through NPR1 (natriuretic peptide receptor 1), provokes hypotension. Such hypotension is thought to be due to ANP inducing vasodilation via NPR1 in the vasculature; however, the underlying mechanism remains unclear. Here, we investigated the mechanisms of acute and chronic blood pressure regulation by ANP.

METHODS AND RESULTS

Immunohistochemical analysis of rat tissues revealed that NPR1 was abundantly expressed in endothelial cells and smooth muscle cells of small arteries and arterioles. Intravenous infusion of ANP significantly lowered systolic blood pressure in wild-type mice. ANP also significantly lowered systolic blood pressure in smooth muscle cell-specific Npr1-knockout mice but not in endothelial cell-specific Npr1-knockout mice. Moreover, ANP significantly lowered systolic blood pressure in Nos3-knockout mice. In human umbilical vein endothelial cells, treatment with ANP did not influence nitric oxide production or intracellular Ca²⁺ concentration, but it did hyperpolarize the cells. ANP-induced hyperpolarization of human umbilical vein endothelial cells was inhibited by several potassium channel blockers and was also abolished under knockdown of RGS2 (regulator of G-protein signaling 2), an GTPase activating protein in G-protein α-subunit. ANP increased Rgs2 mRNA expression in human umbilical vein endothelial cells but failed to lower systolic blood pressure in Rgs2-knockout mice. Endothelial cell-specific Npr1-overexpressing mice exhibited lower blood pressure than did wild-type mice independent of RGS2, and showed dilation of arterial vessels on synchrotron radiation microangiography.

CONCLUSIONS

Together, these results indicate that vascular endothelial NPR1 plays a crucial role in ANP-mediated blood pressure regulation, presumably by a mechanism that is RGS2-dependent in the acute phase and RGS2-independent in the chronic phase.

D-Cysteine supplementation partially protects against ferroptosis induced by xCT dysfunction via increasing the availability of glutathione

Glutathione (GSH) is synthesized from three amino acids and the overall process is highly dependent on the availability of l-cysteine (l-Cys). GSH serves as an essential cofactor for glutathione peroxidase 4 (Gpx4), which reduces phospholipid hydroperoxides. The inactivation of Gpx4 or an insufficient supply of l-Cys results in the accumulation of lipid hydroperoxides, eventually leading to iron-dependent cell death, ferroptosis. In this study, we investigated the anti-ferroptotic properties of d-cysteine (d-Cys) under conditions of dysfunction in cystine transporter, xCT. l-Cys supplementation completely rescued ferroptosis that had been induced by the erastin-mediated inhibition of xCT in Hepa 1-6 cells. Upon d-Cys supplementation, the erastin-treated cells remained completely viable for periods of up to 24 h but eventually died after 48 h. d-Cys supplementation suppressed the production of lipid peroxides, thereby ferroptosis. The addition of d-Cys sustained intracellular Cys and GSH levels to a certain extent. When Hepa 1-6 cells were treated with a combination of buthionine sulfoximine and erastin, the anti-ferroptotic effect of d-Cys was diminished. These collective results indicate that, although d-Cys is not the direct source of GSH, d-Cys supplementation protects cells from ferroptosis in a manner that is dependent on GSH synthesis via stimulating the uptake of l-Cys.

A Review of Coagulation Abnormalities of Autoimmune Acquired Factor V Deficiency with a Focus on Japan

Coagulation factor V (or FV for the purpose of medical safety) is an essential cofactor of coagulation factor X in the common pathway of coagulation; severe FV deficiency leads to a bleeding tendency. Although both congenital and acquired FV deficiencies are widely recognized, FV deficiency also presents as an autoimmune disorder. A nationwide survey on autoimmune coagulation factor deficiencies (AiCFDs) conducted in Japan by our Japanese Collaborative Research Group identified 24 new patients with autoimmune FV deficiency (AiFVD) in the past 5 years. Furthermore, our extensive literature search confirmed that 177 AiFVD cases have been reported in previous articles published from Japan. Patients with AiFVD in Japan were predominantly men, with age similar to those with other AiCFDs. AiFVD was confirmed as a relatively mild type of bleeding diathesis, associated with lower mortality rate than that for AiFVD and other AiCFDs reported in previous studies. Patients with AiFVD had variable FV inhibitor titers and both neutralizing anti-FV autoantibodies and nonneutralizing counterparts. Although spontaneous resolution occurs in some patients, timely initiation of hemostatic and immunosuppressive therapies helps arrest the bleeding and eliminate anti-FV antibodies, resulting in a high cumulative recovery rate. Immunological anti-FV antibody detection is recommended to avoid missing AiFVD cases for the presence of nonneutralizing anti-FV autoantibodies. Further investigation is necessary to clarify the long-term prognosis and optimal management of AiFVD.

Important roles of the human leukocyte antigen class I and II molecules and their associated genes in the autoimmune coagulation factor XIII deficiency via whole-exome sequencing analysis

Autoimmune coagulation factor XIII deficiency is a bleeding disorder caused by the formation of autoantibodies against the coagulation factor XIII (FXIII); however, the molecular mechanism underlying this process is unknown. Therefore, in the present study, we aimed to elucidate this mechanism by performing whole-exome sequencing analysis of 20 cases of autoimmune FXIII deficiency. We identified approximately 21,788–23,916 variants in each case. In addition to their ability to activate T cells, present antigens, and immune tolerance, the candidate alleles were further narrowed down according to their allelic frequencies and the magnitude of damage caused by the substitution of amino acids. After selecting 44 candidate alleles, we investigated whether they were associated with the FXIII inhibitory titers and/or the anti-FXIII autoantibodies. We found that two polymorphisms whose variant allele frequencies were significantly lower in the patients tended to decrease FXIII inhibitory titers as the number of variant alleles increased. We also found that five polymorphisms whose variant allele frequencies were significantly higher in the patients tended to increase the levels of the anti-FXIII autoantibodies as the number of variant alleles increased. All of these polymorphisms were found in the human leukocyte antigen (HLA) class I and II molecules and their associated genes. In particular, the HLA class II molecule and its associated genes were found to be involved in the presentation of foreign antigens as well as the negative regulation of the proliferation of T-cells and the release of cytokines. Polymorphisms in the HLA class II molecules and the cytotoxic T lymphocyte antigen 4 have been reported to be associated with the development of autoantibodies in acquired hemophilia A. Therefore, we hypothesized that these polymorphisms may be associated with the development of autoantibodies in autoimmune FXIII deficiency.

Urinary and plasma proteomics to discover biomarkers for diagnosing between diabetic nephropathy and minimal change nephrotic syndrome or membranous nephropathy

The choice of treatment for primary nephrotic syndrome depends on the pathologic type of the disorder. Renal biopsy is necessary for a definitive diagnosis, but it is burdensome for the patients, and can be avoided if tests could be performed using urine or plasma. In this study, we analyzed 100 urinary proteins, 141 plasma proteins, and 57 urine/plasma ratios in cases of diabetic nephropathy (DN; n = 11), minimal change nephrotic syndrome (MCNS; n = 14), and membranous nephropathy (MN; n = 23). We found that the combination of urinary retinol-binding protein 4 and SH3 domain-binding glutamic acid-rich-like protein 3 could distinguish between MCNS and DN, with an area under the curve (AUC) of 0.9740. On the other hand, a selectivity index (SI) based on serotransferrin and immunoglobulin G, which is often used in clinical practice, distinguished them with an AUC of 0.9091. Similarly, the combination of urinary afamin and complement C3 urine/plasma ratio could distinguish between MN and DN with an AUC of 0.9842, while SI distinguished them with an AUC of 0.8538. Evidently, the candidates identified in this study were superior to the SI method. Thus, the aim was to test these biomarkers for accurate diagnosis and to greatly reduce the burden on patients.

•

Renal biopsy is necessary for a definitive diagnosis of primary nephrotic syndrome.

•

Renal biopsy is a heavy burden for patients, and a less burdensome test is desired.

•

We discovered at least 6 diagnostic biomarkers using urinary and plasma proteomics.

•

Combination allowed to judge the disease more accurately than selectivity index.

Association between milk and yogurt intake and mortality: a community-based cohort study (Yamagata study)

Background

Dairy products are known as health-promoting foods. This study prospectively examined the association between milk and yogurt intake and mortality in a community-based population.

Methods

The study population comprised of 14,264 subjects aged 40–74 years who participated in an annual health checkup. The frequency of yogurt and milk intake was categorized as none (< 1/month), low (< 1/week), moderate (1–6/week), and high (> 1/day) intake. The association between yogurt and milk intake and total, cardiovascular, and cancer-related mortalities was determined using the Cox proportional hazards model.

Results

During the follow-up period, there were 265 total deaths, 40 cardiovascular deaths and 90 cancer-related deaths. Kaplan–Meier analysis showed that the total mortality in high/moderate/low yogurt intake and moderate/low milk intake groups was lower than that in none group (log-rank, P < 0.01). In the multivariate Cox proportional hazard analysis adjusted for possible confounders, the hazard ratio (HR) for total mortality significantly decreased in high/moderate yogurt intake group (HR: 0.62, 95% confidence interval [CI]: 0.42–0.91 for high intake, HR: 0.70, 95%CI: 0.49–0.99 for moderate intake) and moderate milk intake group (HR: 0.67, 95% CI: 0.46–0.97) compared with the none yogurt and milk intake groups. A similar association was observed for cancer-related mortality, but not for cardiovascular mortality.

Conclusions

Our study showed that yogurt and milk intake was independently associated with a decrease in total and cancer-related mortalities in the Japanese population.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40795-021-00435-1.

Autoimmune Coagulation Factor X Deficiency as a Rare Acquired Hemorrhagic Disorder: A Literature Review

Coagulation factor X (F10) amplifies the clotting reaction in the middle of the coagulation cascade, and thus F10 deficiency leads to a bleeding tendency. Isolated acquired F10 deficiency is widely recognized in patients with immunoglobulin light-chain amyloidosis or plasma cell dyscrasias. However, its occurrence as an autoimmune disorder is extremely rare. The Japanese Collaborative Research Group has been conducting a nationwide survey on autoimmune coagulation factor deficiencies (AiCFDs) starting in the last decade; we recently identified three patients with autoimmune F10 deficiency (AiF10D). Furthermore, an extensive literature search was performed, confirming 26 AiF10D and 28 possible cases. Our study revealed that AiF10D patients were younger than patients with other AiCFDs; AiF10D patients included children and were predominantly male. AiF10D was confirmed as a severe type of bleeding diathesis, although its mortality rate was not high. As AiF10D patients showed only low F10 inhibitor titers, they were considered to have nonneutralizing anti-F10 autoantibodies rather than their neutralizing counterparts. Accordingly, immunological anti-F10 antibody detection is highly recommended. Hemostatic and immunosuppressive therapies may help arrest bleeding and eliminate anti-F10 antibodies, leading to a high recovery rate. However, further investigation is necessary to understand the basic characteristics and proper management of AiF10D owing to the limited number of patients.

Pathological coagulation parameters in as many as 54 patients with autoimmune acquired factor XIII deficiency due to anti-factor XIII autoantibodies

INTRODUCTION

Autoimmune factor XIII (FXIII) deficiency (AiF13D) due to anti-FXIII autoantibodies is an extremely rare, life-threatening bleeding disorder that mostly occurs in the elderly. The number of patients diagnosed with AiF13D has been increasing in Japan, probably because of the nationwide survey on AiF13D supported by the Japanese Ministry of Health, Labour and Welfare.

AIM

To explore the pathologic characteristics of coagulation parameters in AiF13D.

METHODS

AiF13D-suspected cases were consulted, and underwent unified/integrated coagulation screening and were definitively diagnosed as AiF13D separately.

RESULTS

AiF13D patients had lower FXIII antigen levels than non-AiF13D patients, but their values overlapped. Among a series of 22-item screening tests and their resulting parameters, the 'FXIII inhibitory potential' yielded by a 1:1 mixing test of the patient's and healthy control's plasma and its 'residual FXIII activity' in 54 AiF13D cases were most distinguishable from 139 non-AiF13D cases, followed by FXIII activity per se and FXIII-specific activity. While the cross-linked α₂ -plasmin inhibitor level reduced, the levels of D-dimer, fibrin/fibrinogen degradation products and plasmin-plasmin inhibitor complex increased, probably because the patients' haematoma nonspecifically induced secondary fibrinolysis in both AiF13D and non-AiF13D patients.

CONCLUSION

AiF13D appears to induce a hypocoagulopathy combined with a hyper-fibrinolytic state secondary to severe FXIII deficiency caused by anti-FXIII autoantibodies, and the consequent bleeding further modifies its pathological conditions. In addition, the 1:1 mixing test of FXIII activity was confirmed to be a reliable screening method for AiF13D, especially when its derivative parameter, such as the 'FXIII inhibitory potential' or 'FXIII inhibitory potential ratio', is employed.

Impact of east Japan earthquake disaster with massive tsunami for prevalence of Takotsubo syndrome – a multicenter regional registry before and after east Japan earthquake disaster

Background

Previous studies demonstrated Takotsubo syndrome (TS) was easy provoked by earthquake disaster. However, a previous other regional report demonstrated TS was not increased after 2011 east Japan earthquake disaster. The purpose of this study was to clarify incidence of TS after the earthquake disaster in Iwate prefecture during long term period.

Method

Consecutive hospitalized TS patients were registered during 8 years between 2009 and 2016 in our medical university and five Iwate prefecture hospitals. Moreover, patients were divided into two groups, i.e., those with the inland and those with tsunami-stricken area groups. Prevalence of TS were calculated by standard incidence ratio (SIR) before and after the earthquake disaster. Moreover, long-term prognosis in the both groups was compared using Kaplan-Meier analysis.

Results

A total of 112 TS (male 25 and female 87) were registered from acute coronary syndrome registry in each hospital (n=4,163). Averaged age was 75.3 year-old. A total number of TS just after the two months of the earthquake (March and April 2011) was nine and significance monthly variation was observed comparing with the other months (p=0.029). SIR before and after the disaster is as following Figure. There were no significant differences for long-term prognosis between the two groups (p=0.20).

Conclusion

Incidence of TS was increased in acute phase after east Japan earthquake disaster. However, significance increases were maintained during long-term period, although number of TS was decreased after acute phase. TS is increased not only acute but also chronic phase after the serious earthquake disaster.

Standard incidence ratio

Funding Acknowledgement

Type of funding source: None

[Successful management of acquired factor V deficiency developing shortly after induction of hemodialysis]

Autoimmune factor V deficiency (AiF5D) is caused by autoantibodies to coagulation factor V (FV); its clinical manifestations range from asymptomatic to fatal hemorrhage. Herein, we report the case of a 68-year-old man who was diagnosed with end-stage renal disease at the time of a femoral fracture and developed AiF5D after initiating hemodialysis. A wound infection that occurred after joint replacement was treated with antibiotics; however, it was poorly controlled. One month after the procedure, his coagulation time prolonged. The infection was improved by debridement and antibiotics; however, the coagulation time was not decreased and poor hemostasis at the shunt was still persistent. Because ELISA detected anti-FV-binding IgG with FV activity of <2.8% and FV inhibitor levels were 11.8 BU/ml, AiF5D was diagnosed. Oral prednisolone (PSL) was started. Dialysis was initially performed without anticoagulants, but blood clots were not found in the circuit. Anticoagulants were resumed when the coagulation time decreased. After achieving complete remission, PSL dose was tapered and finally discontinued. Few reports have described the management of AiF5D via dialysis. We consider that our report would be useful for the management of patients with similar manifestations.

Discovery of novel biomarkers for atherosclerotic aortic aneurysm through proteomics-based assessment of disease progression

Since aortic aneurysms (AAs) are mostly asymptomatic, but they have a high mortality rate upon rupture, their detection and progression evaluation are clinically important issues. To discover diagnostic biomarkers for AA, we performed proteome analysis of aortic media from patients with thoracic atherosclerotic AA (TAAA), comparing protein levels between the aneurysm and normal tissue areas. After hierarchical clustering analysis of the proteome analysis data, tissue samples were classified into three groups, regardless of morphological features. This classification was shown to reflect disease progression stage identified by pathological examination. This proteomics-based staging system enabled us to identify more significantly altered proteins than the morphological classification system. In subsequent data analysis, Niemann-Pick disease type C2 protein (NPC2) and insulin-like growth factor-binding protein 7 (IGFBP7) were selected as novel biomarker candidates for AA and were compared with the previously reported biomarker, thrombospondin 1 (THBS1). Blood concentrations of NPC2 and IGFBP7 were significantly increased, while THBS1 levels were decreased in TAAA and abdominal atherosclerotic AA patients. Receiver operating characteristic analysis of AA patients and healthy controls showed that NPC2 and IGFBP7 have higher specificity and sensitivity than THBS1. Thus, NPC2 and IGFBP7 are promising biomarkers for the detection and progression evaluation of AA.

Deficiency of Cardiac Natriuretic Peptide Signaling Promotes Peripartum Cardiomyopathy-Like Remodeling in the Mouse Heart

BACKGROUND

The maternal circulatory system and hormone balance both change dynamically during pregnancy, delivery, and the postpartum period. Although atrial natriuretic peptides and brain natriuretic peptides produced in the heart control circulatory homeostasis through their common receptor, NPR1, the physiologic and pathophysiologic roles of endogenous atrial natriuretic peptide/brain natriuretic peptide in the perinatal period are not fully understood.

METHODS

To clarify the physiologic and pathophysiologic roles of the endogenous atrial natriuretic peptide/brain natriuretic peptide-NPR1 system during the perinatal period, the phenotype of female wild-type and conventional or tissue-specific Npr1-knockout mice during the perinatal period was examined, especially focusing on maternal heart weight, blood pressure, and cardiac function.

RESULTS

In wild-type mice, lactation but not pregnancy induced reversible cardiac hypertrophy accompanied by increases in fetal cardiac gene mRNAs and ERK1/2 (extracellular signaling-regulated kinase) phosphorylation. Npr1-knockout mice exhibited significantly higher plasma aldosterone level than did wild-type mice, severe cardiac hypertrophy accompanied by fibrosis, and left ventricular dysfunction in the lactation period. Npr1-knockout mice showed a high mortality rate over consecutive pregnancy-lactation cycles. In the hearts of Npr1-knockout mice during or after the lactation period, an increase in interleukin-6 mRNA expression, phosphorylation of signal transducer and activator of transcription 3, and activation of the calcineurin-nuclear factor of the activated T cells pathway were observed. Pharmacologic inhibition of the mineralocorticoid receptor or neuron-specific deletion of the mineralocorticoid receptor gene significantly ameliorated cardiac hypertrophy in lactating Npr1-knockout mice. Anti-interleukin-6 receptor antibody administration tended to reduce cardiac hypertrophy in lactating Npr1-knockout mice.

CONCLUSIONS

These results suggest that the characteristics of lactation-induced cardiac hypertrophy in wild-type mice are different from exercise-induced cardiac hypertrophy, and that the endogenous atrial natriuretic peptide/brain natriuretic peptide-NPR1 system plays an important role in protecting the maternal heart from interleukin-6-induced inflammation and remodeling in the lactation period, a condition mimicking peripartum cardiomyopathy.

Lipidomic signatures of aortic media from patients with atherosclerotic and nonatherosclerotic aneurysms

Aortic aneurysms are associated with fatal aortic rupture. Current therapeutic approaches are limited to implantation of aortic prostheses and stent-grafts; no effective drugs are available because the pathogenic mechanisms of aortic aneurysms remain unclear. Here, we aimed to elucidate the molecular mechanisms of the initiation and progression of aortic aneurysm by lipidomics. We performed lipidomics analyses of lipids in the aortic media of normal, border, and aneurysm areas from patients with thoracic atherosclerotic aortic aneurysm (N = 30), thoracic nonatherosclerotic aortic aneurysm (N = 19), and abdominal atherosclerotic aortic aneurysm (N = 11) and from controls (N = 8) using liquid chromatography and mass spectrometry. Significant alterations were observed in the lipid profiles of patients with atherosclerotic aortic aneurysms and to a lesser extent in those with nonatherosclerotic aneurysms. Increased triacylglycerols (TGs) and decreased ether-type phosphatidylethanolamines (ePEs) were observed throughout the normal, border, and aneurysm areas of thoracic and abdominal atherosclerotic aortic aneurysms. Prostaglandin D₂ increased, but ePEs and TGs decreased in normal areas of thoracic atherosclerotic aortic aneurysms and thoracic nonatherosclerotic aortic aneurysms compared with the control tissues. These findings expand our knowledge of metabolic changes in aortic aneurysms and provide insights into the pathophysiology of aortic aneurysms.

Reliability of ultrasonographic measurements of bovine sole structures in relation to sole horn thickness, measured by computed tomography, and sole horn hardness

The goal of the present study was to determine the effect of sole horn thickness (SHT) and sole horn hardness (SHD) on ultrasonographic visualization of sole structures in the inner and outer claws of 150 Holstein-Friesian cows, and to evaluate different ultrasound frequencies for this purpose. Ultrasonographic views of the sole structure were considered complete when 3 echogenic lines, representing the ventral surface of the sole horn, the borders of the sole horn and soft-tissue layer, and the ventral surface of the distal phalanx, were seen. The proportion of complete ultrasonographic views of the sole structures, designated as the ultrasonographic visualization proportion (UVP), and the measurement errors of SHT were evaluated by comparing images from computed tomography (CT) and ultrasonography. The latter images were generated using 3 different probes, frequencies of 6.5 and 5.0 MHz, and 2 different ultrasound machines (#1 and #2) to assess the apex, middle, and heel regions of the claws. The UVP were 60.8 to 77.9% for the 6.5-MHz probe in ultrasound machine #1 (probe A), which were lower than those (>90%) for both the 5.0-MHz probe in ultrasound machine #1 (probe B) and the 5.0-MHz probe in ultrasound machine #2 (probe C). The UVP was significantly lower in claws with an SHD ≥50 units than in claws with an SHD <40 or 40 to <50 units (UVP: 77.1% compared with 93.7 and 91.4%, respectively) when measured with probe B. In claws with an SHT <10 mm, the UVP was significantly lower when SHD was ≥50 units compared with <40 or 40 to >50 units; the values were 69.0% versus 91.3 and 85.9%, respectively, for probe A, and 89.7% versus 100 and 100%, respectively, for probe B. When SHT were measured by either probes A or B in ultrasound machine #1, the proportions of claws in which ultrasonographic values were within a ±1 mm range compared with the values obtained by CT were 84.9 to 91.3% for CT-determined SHT <5 mm, 66.7 to 71.9% for CT-determined SHT 5 to <7 mm, 28.9 to 51.2% for CT-determined SHT 7 to <10 mm, and 6.2 to 19.7% for CT-determined SHT ≥10 mm. The data indicated that increased SHT was associated with a decrease in ultrasonographic measurement accuracy. In claws with an SHT <5 mm, the high proportion of ultrasonographic values that were accurate within a ±1 mm range suggests that this imaging modality would be useful in cows with thin soles.

Generation and Application of Rat Monoclonal Antibodies Specific for a Human Blood Coagulation Protein: von Willebrand Factor

von Willebrand factor (VWF) is a glycoprotein that plays a central role in the initiation of blood coagulation. VWF performs two important functions: it acts as a molecular bridge between platelets and as a carrier for coagulation factor VIII (FVIII). von Willebrand disease (VWD) and acquired von Willebrand syndrome (AVWS) are caused by the absence of and/or abnormality in VWF. The pathophysiology of VWD and AVWS is complex and, therefore, it is difficult to diagnose them by conducting the same laboratory tests in all patients. To develop useful monoclonal antibodies (mAbs) for the diagnosis of VWD and AVWS, rat mAbs against human VWF were generated. Immunoblotting analysis revealed that mAbs recognized the reduced and nonreduced VWF protein and endogenous VWF in normal human plasma. Furthermore, we developed a highly sensitive monoclonal antibody-based sandwich enzyme-linked immunosorbent assay technique. In conclusion, the development of VWF-specific mAbs would be useful in the diagnosis of VWD and AVWS.

Photodynamic detection of a canine glioblastoma using 5-aminolevulinic acid

Photodynamic detection using 5-aminolevulinic acid has been used to identify the surgical margins during resection of human primary brain tumours. Although there are some reports on its use in malignant tumours in veterinary medicine, it has never been used for primary brain tumours. Here we describe a canine glioblastoma that was detected at autopsy with protoporphyrin IX fluorescence induced by orally administered 5-aminolevulinic acid. The fluorescence was strongest towards the centre of the lesion and was absent in normal brain tissue. Moreover, the fluorescence findings were consistent with MRI and histopathological findings. Our findings suggest that photodynamic detection using 5-aminolevulinic acid might be useful for intraoperative fluorescence-guided resection of malignant gliomas in dogs.

Isolation of Endogenous Peptides from Cultured Cell Conditioned Media for Mass Spectrometry

Media conditioned by cultured cells represent an excellent source rich in endogenous peptides. Unbiased mass spectrometric analysis of the constituent peptides provides an opportunity to look into proteolytic events such as bioactive peptide processing, membrane protein ectodomain shedding, or even regulated intramembrane proteolysis. If conducted on a large scale, peptidomics has the potential to pinpoint primary cleavage sites. Here a method is described for isolating peptides from cultured cell conditioned media before mass spectrometry analysis.

Rapid immunochromatographic test for detection of anti-factor XIII A subunit antibodies can diagnose 90 % of cases with autoimmune haemorrhaphilia XIII/13

Autoimmune haemorrhaphilia XIII/13 (AH13) is an acquired lifethreatening bleeding disorder due to anti-factor XIII (FXIII) autoantibodies (auto-Abs). AH13 patients may die of haemorrhage without correct diagnosis and proper treatment because of lack of awareness and the absence of rapid easy-to-use tests specific for this disease. Currently, the definitive diagnosis is established by cumbersome and time-consuming laboratory tests such as dot-blot assays and enzymelinked immunosorbent assays (ELISA), and therefore these tests are generally not carried out. To save AH13 patients’ lives, there is an urgent necessity for developing a rapid test for FXIII auto-Abs. We first generated and characterised mouse monoclonal antibodies (mAb) against human FXIII A subunit (FXIII-A), and then developed a rapid immunochromatographic test (ICT) for detection of anti-FXIII-A auto- Abs using one mAb with a dissociation constant of 9.3 × 10-11 M. The auto-Ab-FXIII-A complex was captured by the mAb on a nitrocellulose membrane and visualised by Au-conjugated anti-human IgG Ab. Mixing with healthy control plasma improved the detection of auto-Abs in patients having extremely low levels of FXIII-A. The specificity and sensitivity of the ICT were 87% and 94%, respectively. We also detected auto-Abs against activated FXIII (FXIIIa) in three patients by pre-converting FXIII to FXIIIa by thrombin treatment. ICT values were significantly inversely correlated with FXIII activity levels, indicating an association between the quantity of anti-FXIII autoantibodies and AH13. This reliable rapid ICT assay can be applied to a point-of-care test to detect anti-FXIII-A auto-Abs, and will contribute to early diagnosis and treatment of AH13.

Successful Management of a Patient with Autoimmune Hemorrhaphilia due to Anti-Factor XIII/13 Antibodies Complicated by Pulmonary Thromboembolism

Autoimmune hemophilia-like disease (hemorrhaphilia) due to anti-factor XIII (FXIII) antibodies (AH13) is a very rare, life-threatening bleeding disorder. A 77-year-old woman developed macrohematuria and a right renal pelvic hematoma. The coagulation times were not prolonged, but FXIII activity and antigen levels were severely and moderately reduced to 9 and 29% of normal values, respectively. Accordingly, the FXIII-specific activity turned out to be low. FXIII inhibitor and anti-FXIII-A subunit autoantibodies were detected by a 1:1 crossmixing test and immunoblot and immunochromatographic assays. She was therefore diagnosed with "definite AH13" and treated with plasma-derived FXIII concentrates to arrest the hemorrhage. In addition to a highly compressed inferior vena cava by a huge renal pelvic hematoma, deep vein thrombosis (DVT) and pulmonary thromboembolism (PE) were identified by systemic computed tomography. The patient was immediately started on anticoagulation therapy with low-dose heparin. Emboli disappeared quickly, probably because under-crosslinked thrombi caused by severe FXIII deficiency are vulnerable to fibrinolysis. After about 1.5 years, anti-FXIII-A subunit autoantibodies still remained despite the use of rituximab, steroid pulse therapy, oral prednisolone, and oral cyclophosphamide treatments. In conclusion, an extremely rare AH13 case complicated by DVT and PE was successfully managed by balancing anticoagulation therapy with hemostatic therapy.