Method for Depletion of IgG and IgM from Human Serum as Naive Complement Source.

Understanding how human complement proteins interact with human antibodies is important for the development of antibody therapies and understanding autoimmune diseases. At present, many groups use baby rabbit serum as a source of complement because, in contrast to human serum, it lacks preexisting antibodies. However, for characterization of human (monoclonal) antibodies, human serum would be a preferred source of complement. To prevent complement activation via naturally occurring antibodies, this human serum ideally lacks IgG and IgM. Here we describe how to deplete human serum of naturally occurring IgG and IgM using fast protein liquid affinity chromatography (FPLC) while minimizing the loss of serum complement activity. We also describe assays that can be used to validate depletion of IgG and IgM (IgG, IgM, and C1q sandwich ELISAs) and functionally assess remaining serum complement activity (hemolytic assays CH50 and AH50). Finally, we demonstrate how captured IgG and IgM can be purified.

Hemolytic Tests Exploring Factor H Functional Activities.

Impairment of the complement regulatory protein Factor H (FH) is implicated in the physiopathological mechanisms of different diseases like atypical hemolytic and uremic syndrome and C3 glomerulopathies. It may be due to genetic abnormalities or acquired with the development of autoantibodies. FH has several ligands; therefore, the exploration of its functions requires to perform different tests. Among them, two hemolytic tests are very useful because they give specific and complementary information about FH functions. The first one is dedicated to explore the FH capacity to dissociate the alternative pathway C3 convertase, whereas the second one is designed to explore the capacity of FH to bind cell surfaces and to protect them from complement attack. This chapter describes the procedures to perform these two hemolytic tests, exploring in a complementary way the FH functionality.

Sheep Erythrocyte Preparation for Hemolytic Tests Exploring Complement Functional Activities.

Sheep erythrocytes (SE) are commonly used in complement functional tests. Non sensitized SE are useful to study the FH activity of cell protection. Indeed, as the cell surface of sheep erythrocytes is rich in sialic acids, Factor H (FH) is able to bind on it and therefore they represent a model of nonactivating surface. Because of their high capacity of complement regulation SE need to be modified to explore other functionality of the complement pathways, like the Complement hemolytic 50 (CH50) or the AP C3 convertase decay assays. For these tests, SE are sensitized with an anti-sheep red blood cell stroma antibody. In presence of serum or plasma complement components, sensitized SE may initiate complement cascade activation via the classic pathway explored in the CH50 assay. Sensitized SE may also be used to prepare C3b-coated SE that, with the use of buffers favoring AP, are suitable for the C3 Nef hemolytic assay and for the hemolytic assay studying the AP decay activity of FH. In this chapter we describe how to prepare SE for these different hemolytic tests.

Functional Hemolytic Test for Complement Alternative Pathway Convertase Activity.

The complement system is a key part of innate immunity. However, if the system becomes dysregulated, damage to healthy host cells can occur, especially to the glomerular cells of the kidney. The convertases of the alternative pathway of the complement system play a crucial role in complement activation. In healthy conditions, their activity is strictly regulated. In patients with diseases caused by complement alternative pathway dysregulation, such as C3 glomerulopathy and atypical hemolytic uremic syndrome, factors can be present in the blood that disturb this delicate balance, leading to convertase overactivity. Such factors include C3 nephritic factors, which are autoantibodies against the C3 convertase that prolong its activity, or genetic variants resulting in a stabilized convertase complex. This chapter describes a method in which the activity and stability of the alternative pathway convertases can be measured to detect aberrant serum factors causing convertase overactivity.

Detection of C3 Nephritic Factor by Hemolytic Assay.

C3 nephritic Factor (C3NeF) is autoantibody that binds neoepitopes of the C3 convertase C3bBb, resulting in a stabilization of the enzyme. First functional characterizations of C3NeF were performed by hemolytic assays using preactivated sheep erythrocytes (bearing C3b). Sheep erythrocytes are beforehand sensitized with an anti-sheep red blood cell stroma antibody produced in rabbit (hemolysin). Sensitized sheep erythrocytes will initiate cascade complement activation via the classic pathway, followed by alternative pathway amplification loop, resulting in C3b covalent binding to cell surface. Sheep erythrocytes bearing C3b permit the alternative pathway exploration, in particular decay of alternative pathway C3 convertase.

Cut-off values of immunological tests to identify patients at high risk of severe lupus nephritis.

Cut-off values for anti-dsDNA, anti-nucleosome and anti-C1q antibodies tests and for complementmediated hemolytic activity (CH50) were explored to identify patients with high risk of developing severe lupus nephritis (LN). Forty-one patients with confirmed systemic lupus erythematosus (SLE) were identified; their levels for the three antibodies and complement had been measured on a same serum sample. These patients were classified based on the presence of renal involvem ent; sixteen had active proliferative LN. With the cut-off values accepted in the laboratory for SLE diagnosis (anti-dsDNA > 100 UI/ml, anti-nucleosome > 50 U/ml or CH50 < 190 UCH50%) no significant differences were found between patients with and without LN. Anti-C1q > 40 U/ml showed a statistically significant association with LN and had 80% of specificity. Cut-off values for LN identified by Receiver Operating Characteristic curves (ROC) were higher for anti-dsDNA (> 455 IU/ml) and antinucleosome (>107 U/ml), lower for CH50 (< 150 UCH50%) and, for anti-C1q (> 41 U/ml) coincided with the cut-off values accepted for SLE. Anti-C1q > 134 U/ml had a 92% of specificity, 56% of sensibility and was associated with a fifteen-fold increased risk of LN. The simultaneous presence of anti-nucleosome > 107 U/ml and anti-C1q > 134 U/ml was associated with a 27-fold higher probability for LN. According to these results, the cut-off values used to detect SLE activity could be inadequate to identify patients at high risk of severe LN.

Diagnostic Utility of Complement Serology for Atypical Hemolytic Uremic Syndrome.

OBJECTIVE: To investigate the clinical utility of a 9-analyte complement serology panel (COMS) covering complement function (CH50 and AH50), components (C3, C4), factor B (CFB), factor H, and activation markers (C4d, Bb, and soluble membrane attack complex) for the diagnosis of atypical hemolytic uremic syndrome (aHUS). METHODS: Physician orders for COMS from January 19, 2015, through November 4, 2016, were reviewed. Demographic characteristics, patient diagnosis, and laboratory parameters were recorded. RESULTS: There were 177 COMS orders for 147 patients. The median patient age was 44.9 years (range, 0.9-88.0 years). Common reasons for ordering COMS included monitoring and diagnosis of C3 glomerulopathy and renal dysfunction and differentiation of aHUS from other thrombotic microangiopathies (TMAs). Forty-four patients had COMS ordered for TMAs: 8 had aHUS and all had 1 or more abnormalities within the alternative pathway of complement. Although the sensitivity of this finding for the diagnosis of aHUS is 100%, the specificity is only 28%, with a positive likelihood ratio of 1.39. Patients with aHUS had lower CH50, C3, and CFB than did those with secondary non-aHUS TMA (all P<.01). A combined CFB of 20.9 mg/dL or less and CH50 of 56% or less led to sensitivity of 75% with increased specificity of 88.9% and a diagnostic odds ratio of 24. CONCLUSION: A COMS abnormality should not be interpreted in isolation. In conjunction with clinical presentation, a decrease in both CFB and CH50 may be an important clue to support the diagnosis of aHUS.

Cut-off values of immunological tests to identify patients at high risk of severe lupus nephritis

Cut-off values for anti-dsDNA, anti-nucleosome and anti-C1q antibodies tests and for complement-mediated hemolytic activity (CH50) were explored to identify patients with high risk of developing severe lupus nephritis (LN). Forty-one patients with confirmed systemic lupus erythematosus (SLE) were identified; their levels for the three antibodies and complement had been measured on a same serum sample. These patients were classified based on the presence of renal involvem ent; sixteen had active proliferative LN. With the cut-off values accepted in the laboratory for SLE diagnosis (anti-dsDNA > 100 UI/ml, anti-nucleosome > 50 U/ ml or CH50 < 190 UCH50%) no significant differences were found between patients with and without LN. Anti-C1q > 40 U/ml showed a statistically significant association with LN and had 80% of specificity. Cut-off values for LN identified by Receiver Operating Characteristic curves (ROC) were higher for anti-dsDNA (> 455 IU/ml) and anti-nucleosome (>107 U/ml), lower for CH50 (< 150 UCH50%) and, for anti-C1q (> 41 U/ml) coincided with the cut-off values accepted for SLE. Anti-C1q > 134 U/ml had a 92% of specificity, 56% of sensibility and was associated with a fifteen-fold increased risk of LN. The simultaneous presence of anti-nucleosome > 107 U/ml and anti-C1q > 134 U/ml was associated with a 27-fold higher probability for LN. According to these results, the cut-off values used to detect SLE activity could be inadequate to identify patients at high risk of severe LN.

Se exploraron valores de corte para los ensayos de anti-ADNdc, anti-nucleosoma, anti-C1q y complemento hemolítico total (CH50) capaces de identificar los casos con mayor riesgo de nefritis lúpica (NL) grave. Se seleccionaron 41 pacientes ≥ 16 años con lupus eritematoso sistémico (LES) confirmado que tenían titulados los niveles de los tres anticuerpos y CH50, en una misma muestra de suero. Fueron clasificados según presencia de compromiso renal; 16 presentaron formas proliferativas de NL activa. Con los valores de corte aceptados por el laboratorio para el diagnóstico de LES (anti-ADNdc > 100 UI/ml, anti-nucleosoma > 50 U/ml o un CH50 < 190 UCH50%) no se encontraron diferencias significativas entre casos con y sin NL. Un anti-C1q > 40 U/ml tuvo una especificidad del 80% y mostró una asociación estadísticamente significativa con NL. Al aplicar curvas Receiver Operating Characteristic (ROC) para NL, se identificaron valores de corte más altos para anti-ADNdc (> 455 IU/ml) y anti-nucleosoma (> 107 U/ml), más bajo para CH50 (< 150 UCH50%) y para el anti-C1q (> 41 U/ml) coincidió con el aceptado para diagnóstico de LES. Un anti-C1q > 134 U/ml presentó una sensibilidad del 56%, una especificidad del 92% y se asoció con quince veces más riesgo de NL. La presencia simultánea de anti-C1q > 134 U/ml y anti-nucleosoma > 107 U/ml se asoció 27 veces más riesgo de NL. De acuerdo a estos resultados los valores de corte empleados para actividad en pacientes con LES podrían resultar inadecuados para identificar pacientes con mayor riesgo de NL grave.

Complement systems C4, C3 and CH50 not subject to a circadian rhythm.

BACKGROUND: The circadian fluctuations in the blood levels of selected components of the complement system are ill-defined. Some authors found nadir serum levels of C4 and C3 components, together with C3a at nighttime, while others reported insomnia when pro-inflammatory components exhibited increased serum levels. In this study, we quantitatively estimate the morning and evening daytime serum levels of CH50, C4, C3, put into context with C-reactive protein (CRP), cortisol, parathyroid hormone (PTH) and 25(OH)vitamin D at 07:00 A.M. and at 07:00 P.M. METHODS: Seven healthy adult women and 11 men who were voluntary participants agreed to a fasting venipuncture in the morning after having normally eaten through the day and in the evening. The C4 and C3 serum levels were measured on a Cobas (Roche Diagnostics, Switzerland) modular analyzer, CH50 was estimated using the COMPL300 enzyme-linked immunosorbent assay (ELISA) of Wieslab (Malmö, Sweden). CRP, 25(OH)vitamin D, PTH and cortisol concentrations were assessed with electro-chemiluminescence immunoassay (ECLIA) on the Roche Cobas 6000 platform; IgG was measured using nephelometry (Siemens, Germany). RESULTS: With the exception of higher PTH levels in the evening [3.12-5.46, 95% confidence interval (CI)] compared to the morning (2.93-4.65, 95% CI), the mean and median values of C4, C3, CH50 as well as CRP, PTH and 25(OH)vitamin D fell within the established reference intervals. Cortisol levels were measured as an internal positive control for diurnal fluctuations (morning: 294-522 nmol/L, 95% CI; evening: 106-136 nmol/L, 95% CI). CONCLUSIONS: The concentrations of the assessed complement components C4 and C3 as well as CH50 surrogate assay did not yield significantly different values between early morning and evening. This does not exclude their participation in the circadian metabolome; this pilot study with healthy participants suggests that patients with an autoimmune disease in remission can give their blood samples independently during daytime with or without fasting.

Maximum Likelihood Estimation of Titer via a Power Family of Four-Parameter Logistic Model.

For many laboratory assays, the readouts are presence or absence of a particular function, and the binary outcomes are correlated. The research interest is often focused on the estimation of titers, at which 50% positivity occurs. The classical approach by Reed and Muench (RM) assumes linear dose-response relationship around the potential titer, and uses only information from two points around the potential titer, which is inefficient in both precision and accuracy. While the model-based methods such as four-parameter logistic regression (4PL) use all the data, they do not consider the correlation among binary outcomes from same identities, which may lead to estimates with overstated precision. We propose estimating titers from two different anchors: independent responses from same identities or exchangeable responses from same identities. Marginal distributions of responses are linked to covariates of dilution factors by the 4PL model for independent responses and by a power family of the 4PL models for exchangeable responses. The maximum-likelihood procedure is used to get estimates of parameters and titers. The superiority of proposed methods over the classical approach is demonstrated both in simulation studies and in analysis of real data from hemagglutination assays.

Complement Factor 3 Could Be an Independent Risk Factor for Mortality in Patients with HBV Related Acute-on-Chronic Liver Failure.

The complement is thought to be involved in the pathogenesis of multiple liver disorders. However, its role in patients with HBV related acute-on-chronic liver failure (HBV-ACLF) remains unclear. Serum levels of the third and fourth complement components (C3, C4) and complement function (CH50) were examined in this prospective, observational study. Associations between their expression and disease activity were analyzed. Survival was analyzed by Kaplan-Meier curves. Predictors of clinical outcome were determined by Cox regression analysis. C3, C4, and CH50 levels were significantly lower in HBV-ACLF patients compared to controls. C3, C4, and CH50 levels were negatively correlated with Tbil levels but positively associated with PTA levels. C3 levels were negatively associated with MELD-Na. C3 levels were significantly lower in HBV-ACLF patients who died compared to patients who survived. In a median hospital stay of 39 days, mortality occurred in 41 patients with a progressive increase based on C3 grade (P = 0.008). The actuarial probability of developing mortality was significantly higher in patients with low C3 grade compared to those with high C3 grade (P < 0.001). Multivariate Cox regression analysis showed that C3 levels were an independent predictor of mortality. Complement played a pathogenic role in HBV-ACLF patients and C3 was an independent predictor of mortality.

Early Serologic Diagnosis of Mycoplasma pneumoniae Pneumonia: An Observational Study on Changes in Titers of Specific-IgM Antibodies and Cold Agglutinins.

There have been some limitations on early diagnosis of Mycoplasma pneumoniae (MP) infection because of no immunoglobulin M (IgM) responses and variable detection rates of polymerase chain reaction in the early stage of the disease. We wanted to discuss regarding early diagnostic method using short-term paired titration of MP-specific IgM and cold agglutinins (CAs) in the early stage of MP pneumonia.The participants of this study were 418 children with MP pneumonia during 2 recent epidemics (2006-2007 and 2011), and they were diagnosed by an anti-MP IgM antibody test (Serodia Myco II) examined twice during hospitalization at presentation and around discharge (mean of 3.4 ±â€Š1.3 days apart). CA titers were simultaneously examined twice during study period. Anti-MP IgM antibody titer ≥1:40 and CA titer ≥1:4 were considered positive, respectively. The relationships between 2 IgM antibodies in the early stage were evaluated.Regarding MP-specific antibody titers, 148 patients showed a seroconversion, 245 patients exhibited increased titers, and 25 patients had unchanged higher titers (≥1:640) during hospitalization. The median MP-specific antibody titers at each examination time were 1:80 and 1:640, respectively; those of CAs were 1:8 and 1:32, respectively. Illness duration prior to admission showed a trend of association with both titers, and patients with shorter illness duration had a higher rate of negative titers or lower titers at each examination time. CAs and MP-specific antibody titers were correlated in the total patients at presentation and at 2nd examination (P < 0.001, respectively), and the diagnostic corresponding rates of CAs to IgM antibody test were 81% to 96% in patient subgroups.Short-term paired MP specific-IgM determinations in the acute stage may be used as a definitive diagnostic method for MP pneumonia. Paired CA titers showed a correlation with MP-specific antibody titers, suggesting they can be used as an adjuvant diagnostic method.

A novel quantitative hemolytic assay coupled with restriction fragment length polymorphisms analysis enabled early diagnosis of atypical hemolytic uremic syndrome and identified unique predisposing mutations in Japan.

For thrombotic microangiopathies (TMAs), the diagnosis of atypical hemolytic uremic syndrome (aHUS) is made by ruling out Shiga toxin-producing Escherichia coli (STEC)-associated HUS and ADAMTS13 activity-deficient thrombotic thrombocytopenic purpura (TTP), often using the exclusion criteria for secondary TMAs. Nowadays, assays for ADAMTS13 activity and evaluation for STEC infection can be performed within a few hours. However, a confident diagnosis of aHUS often requires comprehensive gene analysis of the alternative complement activation pathway, which usually takes at least several weeks. However, predisposing genetic abnormalities are only identified in approximately 70% of aHUS. To facilitate the diagnosis of complement-mediated aHUS, we describe a quantitative hemolytic assay using sheep red blood cells (RBCs) and human citrated plasma, spiked with or without a novel inhibitory anti-complement factor H (CFH) monoclonal antibody. Among 45 aHUS patients in Japan, 24% (11/45) had moderate-to-severe (≥50%) hemolysis, whereas the remaining 76% (34/45) patients had mild or no hemolysis (<50%). The former group is largely attributed to CFH-related abnormalities, and the latter group has C3-p.I1157T mutations (16/34), which were identified by restriction fragment length polymorphism (RFLP) analysis. Thus, a quantitative hemolytic assay coupled with RFLP analysis enabled the early diagnosis of complement-mediated aHUS in 60% (27/45) of patients in Japan within a week of presentation. We hypothesize that this novel quantitative hemolytic assay would be more useful in a Caucasian population, who may have a higher proportion of CFH mutations than Japanese patients.

[Chemical constituents of Rabdosia japonica var. glaucocalyx and their anti-complementary activity].

To study the chemical constituents of Rabdosia japonica var. glaucocalyx and their anti-complementary activity on the basis of preliminary studies. Target isolation guided by anti-complementary activity test, compounds in the chloroform and n-butanol fractions were isolated and purified by silica gel and Sephadex LH-20 column chromatographies, and preparative HPLC. The structures were identified by various spectroscopic data including ESI-MS, 1H-NMR and 13C-NMR data. The compounds were evaluated for anti-complementary activity in vitro. Eleven compounds were isolated from the chloroform and n-butanol soluble fractions and identified as stigmasterol (1), stigmas-9 (11) -en-3-ol (2), glaucocalyxin D (3), kamebakaurin (4), maslinic acid (5), corosolic acid (6), minheryins I (7), diosmetin (8), caffeic acid ethylene ester (9), caffeic acid (10) and vitexin (11). Isoquercetrin, rutin, quercetin, 3-methylquercetin, luteolin, 7-methylluteolin, and apigenin which were isolated from the preliminary studies together with compounds 9 and 10 showed inhibition of the complement system by the classical pathway. Compounds 2, 4, 6-9 and 11 were obtained from this plant for the first time. Caffeic acid (10) showed the strongest activity in vitro with a CH50 value of 0.041 g x L(-1).

Complement factor H functional assay may help to monitor atypical haemolytic uraemic syndrome: a pilot study.

BACKGROUND: Atypical haemolytic uraemic syndrome (aHUS) results from uncontrolled complement system activation. Complement factor H gene mutations are common causes of aHUS. Plasmatherapy, including plasma infusions and/or plasma exchanges, has been tried in this setting with various successes. At present, we lack a specific marker to monitor functional factor H deficiency-related aHUS. METHODS: We report the use of factor H functional assay in three patients with atypical haemolytic uraemic syndrome. This assay is based on the requirement of soluble complement regulators that bind sheep red cells to prevent haemolysis. As factor H is highly abundant in the plasma, its defect results in haemolysis. Factor H activity was also measured among plasma donors. RESULTS: One patient suffered from a plasma-dependent form of atypical haemolytic uraemic syndrome. Plasma exchanges restored higher factor H activity and were associated with a 15-months disease-free period. In the two other patients, one with a failing renal graft and the other on chronic dialysis, a bout of thrombotic microangiopathy was preceded by a drop of haemolytic activity below normal values. Plasma from healthy donors (N=65) showed only minimal variations of Factor H activity (mean activity: 98.3%, SD=4.0). CONCLUSION: These preliminary data suggest that factor H activity could be of interest in both the diagnosis and the treatment by plasmatherapy of factor H-related aHUS.

[Rapid assessment of the complement system reactivity].

The authors developed a new indicator of humoral immunity, which characterizes the complement system reactivity (CSR). Complement system reactivity has been investigated in haemolytic assay using sheep red blood cells, autologous heterophile antibodies and complement in a "load" as 0.29 M NaCl in the system. There has been made a study of blood sera of 10 healthy donors and 20 patients who undergo screening for chronic infections in clinical-diagnostic centers. Inhibition of complement--0.29 M NaCl at a level of 30-70% in healthy donors is taken as an indicator that characterizes normal complement system reactivity of a human serum. Investigations have revealed in 11 patients (55%) of the 20 examined people high complement system reactivity (lysis degree more than 70%), in 6 patients (30%)--normal complement system reactivity, and in 3 patients (15%)--low complement system reactivity (lysis degree less than 30%). Thus, the study of the complement system reactivity in a "load", in the presence of 0.29 M NaCl in the test sample, detects functional changes, both reinforcing and reducing complement activity.

The complement system of the goat: haemolytic assays and isolation of major proteins.

BACKGROUND: The aim of the present study was to develop a haemolytic assay for the study of the complement system in dairy goats (Capra aegagrus hircus) and to characterize the major goat complement system proteins. RESULTS: The commonly used sheep erythrocyte sensitized with rabbit antibodies were not sensitive to lysis by goat serum, but the combination of human red blood cells (RBC) plus rabbit antibodies was the best option found for goat complement assay. A buffer based on HEPES instead of the classical veronal (barbitone) was developed. Three proteins were isolated: factor H, C1q and C3 and these were compared with the corresponding human proteins. A novel affinity chromatography technique was developed for isolation of factor H. CONCLUSIONS: Human RBC plus rabbit antibodies were a suitable option for haemolytic assays. The isolated proteins are similar to the human counterparts.

Suero de conejo con actividad de complemento para tipificación del complejo mayor de histocompatibilidad humano / Rabbit serum with complement activity to typify human major histocompatibility complex

En el ensayo de microlinfocitotoxicidad, el suero de conejo como fuente de complemento desempeña un rol esencial en la clasificación del complejo mayor de histocompatibilidad humano, tanto para la tipificación antigénica como en el cross-match linfocitario de la pareja donante-receptor antes de realizar los trasplantes. En este trabajo, se obtuvieron 3 lotes experimentales de dicho hemoderivado con óptimos indicadores de rendimiento, actividad biológica y estabilidad. El exanguíneo de los animales se realizó por la técnica de yugulación. El suero fue separado por centrifugación en condiciones ambientales y de temperatura controladas. Posteriormente, el producto se sometió a filtración esterilizante y se tomaron muestras para los ensayos de calidad. El estudio mostró que el producto conserva la actividad biológica al menos durante 18 meses y que los valores de citotoxicidad se encuentran dentro de los límites de aceptación para su empleo en los ensayos de histocompatibilidad pretrasplante(AU)

Microlinfocitotoxicity assay is one of the serological methods used to classify human major histocompatibility complex. In this technique the rabbit´s serum as complement source, plays an essential role in antigens determination and in lymphocytes cross match assay as necessary stage before the selection of the best donor-receiver pair to realize the organ transplant. Three experimental lots of normal rabbit serum were developed with excellent indicators of efficiency, biological activity and stability. Rabbit's blood was obtained through jugulating technique and serum was separated by centrifugation in controlled environment and temperature´s conditions. The sterilization process was performed by filtration and the samples were taken for quality´s control assays. Stability studies showed that the product kept the biological activity at least during 18 months after it was processed and cytotoxicity's values were adequate for its employment in histocompatibility pre-transplant assays(AU)