Anti-C1-Inhibitor Autoantibody Detection by ELISA.

Enzyme-linked immunosorbent assay (ELISA) is a quantitative analytical method used to measure the concentration of molecules in biological fluids through antigen-antibody reactions. Here we describe the measurement of anti-C1-inhibitor autoantibodies by an indirect ELISA. In this method patients' sera are incubated in a microplate coated with plasma derived C1-inhibitor.

Acquired C1 esterase inhibitor deficiency in lymphomas: prevalence, symptoms, and response to treatment.

We retrospectively studied the prevalence of C1 esterase inhibitor (C1 INH) deficiency in 131 patients with various lymphomas. We determined C1 INH activity, C1 INH antigen, and C4 concentration at diagnosis and after chemotherapy. In follicular lymphoma (FL), diffuse large B-cell lymphoma (DLBCL) and chronic lymphocytic leukemia (CLL) consecutive patients were studied. In these entities, the prevalence of C1 INH deficiency was 10.2% in DLBCL, 4.1% in CLL, and 0% in FL and Hodgkin lymphoma. In indolent lymphomas, we identified only single cases of C1 INH deficiency, predominantly in splenic marginal zone lymphomas (SMZL) (four cases). Only three patients were symptomatic while the majority (11 cases) was asymptomatic. In DLBCL patients who were successfully treated with chemotherapy, complete normalization of C1 INH activity and C4 was observed. In contrast, C1 INH deficiency remained in SMZL patients after splenectomy. We conclude that C1 INH deficiency in lymphomas is frequently asymptomatic and responsive to immunochemotherapy.

Management of pregnancy and delivery in patients with hereditary angioedema due to C1 inhibitor deficiency

Background and Objective: There is little information on pregnancy and delivery in patients with hereditary angioedema due to C1 inhibitor deficiency (C1INH-HAE). The aim of this study was to describe the effect of pregnancy and deliveries on symptoms of C1INH-HAE and review the need for and safety of treatments available during the study period. Methods: Retrospective review using a purpose-designed questionnaire of 61 C1INH-HAE patients from 5 hospitals specialized in the management of HAE in Spain. The outcomes measured were number of pregnancies, changes in symptoms during pregnancy and delivery, mode of delivery, type of anesthesia during delivery, treatments received, and tolerance of treatments. Results: We reviewed 125 full-term pregnancies (89 without a prior diagnosis of C1INH-HAE), 14 miscarriages, and 4 induced abortions. Patients reported an increased frequency of C1INH-HAE symptoms in 59.2% of pregnancies (74/125) and the presence of symptoms throughout pregnancy in 40% (50/125). Prophylactic C1INH-HAE therapy was used during 9 (7.2%) of the 125 pregnancies. Nine patients—in 11 pregnancies (8.8 %)—received treatment for acute attacks. Most deliveries (n=110, 88%) were vaginal. A cesarean section was necessary in 15 cases (12%). Short-term prophylaxis with pdhC1INH was administered before 14 deliveries (11.2 %); 111 deliveries (88.8 %) were performed without premedication and were well tolerated. Anesthesia was used in 51 deliveries (40.8%). Conclusions: Pregnancy has a variable influence on the clinical expression of C1INH-HAE. Attacks tend to occur more frequently but not to increase in severity. Vaginal delivery was mostly well tolerated. pdhC1INH prophylaxis should be administered prior to cesarean delivery and is also recommended before vaginal delivery if there are additional risk factors. pdhC1INH should always be available in the delivery room (AU)

Antecedentes y Objetivo: Existe escasa información sobre la evolución del embarazo y el parto en pacientes con angioedema hereditario con déficit de C1 Inhibidor (AEH-C1INH). El objetivo del estudio fue describir el efecto de embarazo y parto en los síntomas de AEH-C1INH y la necesidad y seguridad de las terapias disponibles durante dicho período. Diseño: Revisión retrospectiva de datos registrados en 5 centros hospitalarios españoles expertos en AEH. Pacientes y Métodos: 61 mujeres con diagnóstico de AEH-C1INH antes o después de su(s) embarazo(s). Se rellenó un cuestionario específico. Fue evaluado: número de embarazos, evolución de síntomas de AEH durante embarazo(s) y parto(s), tipo de parto, tipo de anestesia durante el parto, tratamientos recibidos y su tolerancia. Resultados: Se revisaron 125 embarazos a término (en 89 embarazos las pacientes estaban sin diagnosticar de AEH) y 18 abortos. Hubo aumento en la frecuencia de síntomas de AEH en 59,2% de embarazos (74/125) y los síntomas estuvieron presentes a lo largo de todos los trimestres en el 40% (50/125). Se usó tratamiento preventivo en 9 de los 125 embarazos (7,2%). Nueve pacientes -en 11 embarazos- (8,8%) recibieron tratamiento para crisis agudas. 110 partos (88%) fueron vaginales, mientras que 15 (12%) fueron cesáreas. Se usó tratamiento profiláctico con concentrado de C1-Inhibidor (pdhC1INH) antes de 14 partos (11,2%). Se completaron 111 partos (88,8%) sin ningún tipo de premedicación y resultaron bien tolerados. Se usó anestesia en 51 partos (41,6%). Conclusiones: La influencia del embarazo en la expresión clínica de la enfermedad es variable, no obstante las crisis tienden a aumentar en frecuencia pero no en gravedad. El parto vaginal fue habitualmente bien tolerado. El pdhC1INH debe administrarse antes de un parto mediante cesárea y también se recomendaría en caso de parto vaginal si existiera algún factor de riesgo adicional. El pdhC1INH debe estar siempre disponible en la sala de partos (AU)

The Levels of the Lectin Pathway Serine Protease MASP-1 and Its Complex Formation with C1 Inhibitor Are Linked to the Severity of Hereditary Angioedema.

C1 inhibitor (C1-INH) is known to form complexes with the lectin complement pathway serine proteases MASP-1 and MASP-2. Deficiency of C1-INH is associated with hereditary angioedema (HAE), an autosomal inherited disease characterized by swelling attacks caused by elevated levels of bradykinin. MASP-1 was shown to cleave high m.w. kininogen into bradykinin; therefore, we hypothesized that MASP-1 levels and the quantity of MASP-1/C1-INH complexes might be associated with different paraclinical and clinical outcomes of HAE. We measured MASP-1 serum concentrations and endogenous MASP-1/C1-INH complex levels in 128 HAE patients and 100 controls. Relatively high levels of pre-existing MASP-1/C1-INH complexes were observed in normal serum, and we found that both the serum levels of MASP-1 and the complex formation between MASP-1 and C1-INH were significantly reduced in HAE patients compared with matched controls (p < 0.0001). The level of MASP-1 and MASP-1/C1-INH complexes in HE patients correlated with the level of C1-INH (p = 0.0009 and p = 0.0047, respectively), the level of C4 (p = 0.0084 and p < 0.0001, respectively), and the number of attacks in the year of blood sampling (p = 0.0075 and p = 0.0058, respectively). In conclusion, we show that MASP-1/C1-INH complexes circulate in normal human blood. The levels of MASP-1 and MASP-1/C1-INH complexes are reduced in HAE patients compared with controls. Both MASP-1 and MASP-1/C1-INH complexes are related to the degree of complement C4 consumption, as well as the severity of disease. These results suggest that MASP-1 may exert a previously unrecognized role in the pathophysiology of HAE.

ELISA to measure neutralizing capacity of anti-C1-inhibitor antibodies in plasma of angioedema patients.

BACKGROUND: Neutralizing autoantibodies (NAbs) against plasma serpin C1-inhibitor (C1-inh) are implicated in the rare disorder, acquired angioedema (AAE). There is insufficient understanding of the process of antibody formation and its correlation with disease progression and severity. We have developed an ELISA for detecting neutralizing capacity of anti-C1-inh positive plasma samples that can be used to study changes in NAb repertoire in patient plasma over the course of disease. METHODS: The ELISA is based on the specific interaction of active C1-inh with its target protease C1s. Decrease in the amount of C1s bound to immobilized C1-inh in the presence of test samples is proportional to the neutralizing capacity of the sample. Assay specificity, intra- and inter-assay variation and assay cut-off are determined using anti-C1-inh antibodies. Assay capability is demonstrated using plasma samples from AAE patients. RESULTS: The assay is specific to a neutralizing anti-C1-inh antibody and shows no interference by a non-neutralizing anti-C1-inh antibody or by the plasma matrix. Intra-assay and inter-assay variations are determined as 17 and 18% respectively. Neutralizing capacity of antibody positive AAE patient plasma samples (n=16) with IgG or IgM type antibodies is readily determined. All samples show positive neutralizing capacity. CONCLUSION: We have developed a robust, specific and semi-quantitative assay to detect the neutralizing capacity of plasma samples containing anti-C1-inh antibodies. This assay can be an important tool for the study of clinical implications of anti-C1-inh NAbs.

Coagulation Factor XII Gene Mutation in Brazilian Families with Hereditary Angioedema with Normal C1 Inhibitor.

BACKGROUND: Hereditary angioedema (HAE) with normal C1 inhibitor (C1-INH) is a rare disorder. Mutations of the gene encoding coagulation factor XII have been identified in a subset of patients with this condition. Our aim was to investigate mutations in the F12 gene in patients with HAE with normal C1-INH from Brazil. METHODS: We studied 5 Brazilian families with index female patients who presented with recurrent angioedema with normal C1-INH and C4 levels. Genomic DNA was isolated from whole blood and PCR was performed. Mutations were detected by the sequencing of exon 9 of the F12 gene and allelic discrimination. RESULTS: The c.983C>A (p.Thr328Lys) mutation was identified in 16 subjects, from 4 of the 5 families studied, including 8 patients with symptoms of HAE with normal C1-INH (87.5% women) and 8 subjects asymptomatic for HAE (25% women). Mean age at onset of symptoms among the FXII-HAE patients was 13.8 years (range 6-25 years). Recurrent abdominal pain (100%) and subcutaneous angioedema (87.5%) were the most frequent clinical presentations. Two patients presented with associated laryngeal edema. In keeping with previous observations in patients with both C1-INH-HAE and HAE with normal C1-INH, all 7 women with FXII-HAE reported triggering or worsening of symptoms upon intake of estrogen-containing oral contraceptives and/or pregnancy. CONCLUSIONS: We report for the first time in Brazil a mutation in the F12 gene as a likely cause of HAE with normal C1-INH in patients with recurrent attacks of angioedema and/or abdominal pain. A higher frequency of abdominal pain attacks and onset of symptoms at a younger age were observed among Brazilian patients when compared to those from other parts of the world.

A novel splice site mutation in the SERPING1 gene leads to haploinsufficiency by complete degradation of the mutant allele mRNA in a case of familial hereditary angioedema.

Hereditary angioedema due to C1-inhibitor deficiency (HAE-C1INH) is a rare autosomal-dominant and life-threatening disorder caused by mutations in SERPING1 gene. It is characterized by attacks of angioedema involving the skin and/or the mucosa of the upper airways, as well as the intestinal mucosa. Here we report the case of a patient with HAE-C1INH without family history of angioedema. By sequencing the SERPING1 gene we detected a novel mutation (c.1249 + 5G > A) affecting the 5' donor splice site in intron 7. We analyzed the SERPING1 cDNA expecting a defect in splicing process but only the wild type allele was detected. SNP analysis of the cDNA sequence demonstrated that only one of the two alleles was present, indicating that the mRNA from the mutated allele was completely degraded. This study reinforces the concept of incomplete penetrance of this disorder since the patients' mother never presented any sign of angioedema despite carrying the same mutation.

Current update on cellular and molecular mechanisms of hereditary angioedema.

OBJECTIVE: To provide an update on the molecular mechanisms of hereditary angioedema (HAE). DATA SOURCES: MEDLINE and PubMed databases were searched to identify pertinent articles using the following key terms: hereditary angioedema, angioedema, C1 inhibitor, bradykinin, contact system, factor XII, mechanism, pathophysiology, severity, permeability, and estrogen. STUDY SELECTIONS: Articles were selected based on their relevance to the subject matter. RESULTS: Although the biochemical basis of "classic" HAE is known to result from C1 esterase inhibitor (C1INH) deficiency, a new form, HAE with normal C1INH, has been identified. HAE types I and II are caused by mutations in the SERPING1 gene that result in decreased plasma levels of functional C1INH. In HAE with normal C1INH, mutations in the F12 gene have been identified in a subset of individuals, but the genetic defect remains unknown in most patients. The primary mediator of swelling in HAE is bradykinin, a product of the plasma contact system that increases vascular permeability. HAE disease severity is highly variable and may be influenced by polymorphisms in other genes and other factors, such as hormones, trauma, stress, and infection. CONCLUSION: Hereditary angioedema is a heterogeneous disorder with a complex pathophysiology. Implicated genes include SERPING1 and FXII in patients with HAE from C1INH deficiency and HAE with normal C1INH levels, respectively. Disease severity is highly variable.

C1 inhibitor: quantification and purification.

C1 inhibitor is a multipotent serpin capable of inhibiting the classical and the lectin pathways of complement, the fibrinolytic system, and contact/kinin system of coagulation. Deficiency of C1 inhibitor manifest as hereditary angioedema (HAE), an autosomal dominant hereditary disease. Measuring the C1 inhibitor level is of vital importance for the diagnosis of HAE and also for monitoring patients receiving C1 inhibitor for therapy. Determination of the antigenic C1 inhibitor level by the radial immunodiffusion (RID) technique is described in detail in this chapter. The presented purification method of plasma C1 inhibitor is primarily based on its high carbohydrate content and its affinity to the lectin jacalin.

Acquired angioedema--occurrence, clinical features and associated disorders in a Danish nationwide patient cohort.

BACKGROUND: The prevalence of acquired angioedema (AAE) is hitherto unknown and, to date, less than 200 patients have been reported worldwide. AAE is associated with lymphoproliferative conditions and autoantibodies against C1 inhibitor (C1INH). Rituximab (RTX) is increasingly used in the treatment of AAE patients. METHODS: A nationwide study of AAE patients was performed in Denmark. Clinical features, associated disorders, treatments and outcomes were registered. RESULTS: Eight AAE patients were identified. The diagnostic delay was on average 1 year and 8 months. Patients were treated with C1INH concentrate or icatibant on demand. Six patients were diagnosed with a clonal B-cell disorder during follow-up, on average 2.5 years after the first swelling. Two patients had monoclonal B-cell lymphocytosis (MBL). Two patients received RTX. CONCLUSIONS: AAE is a rare condition occurring in less than 10% of patients with C1INH deficiency in Denmark. AAE is highly associated with haematologic disorders, and we recommend yearly follow-up visits with clinical examination and blood tests including flow cytometry to diagnose B-cell conditions at an early stage. We report 2 patients with AAE and associated MBL, which is a benign expansion of clonal B lymphocytes. MBL can be the precursor of chronic lymphocytic leukaemia or is associated with non-Hodgkin's lymphoma. If angioedema is poorly controlled with standard treatment regimens, we suggest treatment of the associated haematologic disorder. Based on a review of the literature and our own data, we recommend therapy with RTX, especially in patients with anti-C1INH autoantibodies.

Pathophysiology of hereditary angioedema.

BACKGROUND: Laryngeal angioedema may be associated with significant morbidity and even mortality. Because of the potential severity of attacks, both allergists and otolaryngologists must be knowledgeable about the recognition and treatment of laryngeal angioedema. This study describes the clinical characteristics and pathophysiology of bradykinin-mediated angioedema. METHODS: A literature review was conducted concerning the clinical characteristics and pathophysiology of types I and II hereditary angioedema (HAE), type III HAE, acquired C1 inhibitor (C1INH) deficiency, and angiotensin-converting enzyme (ACE) inhibitor-associated angioedema. RESULTS: The diagnosis of type I/II HAE is relatively straightforward as long as the clinician maintains a high index of suspicion. Mutations in the SERPING1 gene result in decreased secretion of functional C1INH and episodic activation of plasma kallikrein and Hageman factor (FXII) of the plasma contact system with cleavage of high molecular weight kininogen and generation of bradykinin. In contrast, there are no unequivocal criteria for making a diagnosis of type III HAE, although a minority of these patients may have a mutation in the factor XII gene. Angioedema attacks and mediator of swelling in acquired C1INH deficiency are similar to those in type I or II HAE; however, it occurs on a sporadic basis because of excessive consumption of C1INH in patients who are middle aged or older. ACE inhibitor-associated angioedema should always be considered in any patient taking an ACE inhibitor who experiences angioedema. ACE is a kininase, which when inhibited is thought to result in increased bradykinin levels. Bradykinin acts on vascular endothelial cells to enhance vascular permeability. CONCLUSION: Laryngeal swelling is not infrequently encountered in bradykinin-mediated angioedema. Novel therapies are becoming available that for the first time provide effective treatment for bradykinin-mediated angioedema. Because the characteristics and treatment of these angioedemas are quite distinct from each other and from histamine-mediated angioedema, it is crucial that the physician be able to recognize and distinguish these swelling disorders.

Angioedema: an overview and update.

Angioedema is an increasing cause of hospitalizations in the United States. This syndrome presents with non-pitting, asymmetric swelling of the face, lips, tongue, larynx, genitalia, and extremities, although any part of the body can be involved. Common causes of angioedema include allergic reactions and ACE inhibitors. Hereditary angioedema is a rare form of angioedema that can be diagnosed by screening with a C4 level. In 2009, three new treatments for hereditary angioedema were approved for use in the United States, revolutionizing management of this rare disease.

Acquired angioedema: Autoantibody associations and C1q utility as a diagnostic tool.

Acquired Angioedema (AAE) is a rare condition classified into two subtypes: Type I, which is associated with lymphoproliferative disorders, and Type II, which is linked with autoantibodies against C1-esterase inhibitor (C1-INH). Unlike Type I AAE, Type II has no correlation with lymphoproliferative disorders. We report the evaluation of angioedema that was associated with an underlying lymphoproliferative disorder for the purpose of discussing the relationship between C1q and a diagnosis of AAE. A literature review was completed for the purpose of assessing the diagnostic value of C1q when used in the workup of AAE. A PubMed/Web of Science search (1976-2010) produced 78 references (yielding 167 individual cases of AAE) using terminology "AAE." The case described a patient with a depressed C1q (<3.5 mg/dL), decreased C4 (<3 mg/dL), decreased C1-inhibitor (1 mg/dL), decreased functional C1-INH (12%), and decreased total complement (<10 U/mL). Autoantibodies against C1-INH (free and bound respectively) were normal (12.4% and 10.1% of the standard of deviation). Using the above figures and data collected from the literature search, we tabulated 168 individual cases of AAE. Of the 168 cases, C1q was drawn in 104 cases, and 64 cases have no information regarding C1q. There are 10 cases where the C1q was documented as normal. With these values, a correlation between C1q and a diagnosis of AAE was assessed: A decreased C1q correlated with a diagnosis of AAE approximately 56%-94% of the time. C1q is a useful tool when working up a case of AAE.

Pathogenesis and laboratory diagnosis of hereditary angioedema.

Hereditary angioedema (HAE) was first described in the 19th century. Over the past 50 years, many details of the pathophysiology and molecular biology of HAE have been elucidated. Two types of HAE, type I and type II, result from mutations in the gene for the broad-spectrum protease inhibitor C1 inhibitor (C1INH). Type I HAE is characterized by low antigenic and functional C1INH levels and type II HAE has normal antigenic but low functional C1INH levels. Type III HAE, by contrast, has normal antigenic and functional C1INH levels. In some families, type III HAE has been linked to mutations in Hageman factor. C1INH is the primary inhibitor of the complement proteases C1r and C1s as well as the contact system proteases activated Hageman factor (coagulation factor XIIa and XIIf) and plasma kallikrein. It is also an inhibitor of plasmin and coagulation factor XIa. The primary mediator of swelling in HAE has now been unequivocally shown to be bradykinin, generated from activation of the plasma contact system. The knowledge gained concerning the underlying mechanisms of the different types of HAE allow the clinician to approach the laboratory diagnosis with confidence and provides opportunities for novel therapeutic strategies.