Lower complement C1q levels in first-episode psychosis and in schizophrenia

Recent evidence has implicated complement component (C) 4A in excessive elimination of synapses in schizophrenia. C4A is believed to contribute to physiological synapse removal through signaling within the C1q initiated classical activation axis of the complement system. So far, a potential involvement of C1q in the pathophysiology of schizophrenia remains unclear. In this study, we first utilized large-scale gene expression datasets (n = 586 patients with schizophrenia and n = 986 controls) to observe lower C1QA mRNA expression in prefrontal cortex tissue of individuals with schizophrenia (P = 4.8x10-05), while C1QA seeded co-expression networks displayed no enrichment for schizophrenia risk variants beyond C4A. We then used targeted liquid chromatography-mass spectrometry (LS-MS) to measure cerebrospinal fluid (CSF) levels of C1qA in 113 individuals with first-episode psychosis (FEP), among which 66 individuals was later diagnosed with schizophrenia, and 87 healthy controls. CSF concentrations of C1qA were lower in individuals diagnosed with FEP (P = 0.0001), also after removing subjects with a short-term prescription of an antipsychotic agent (P = 0.0005). We conclude that C1q mRNA and protein levels are lower in schizophrenia and that further experimental studies are needed to understand the functional implications.

Antibody Mediated Rejection is not Associated with Worse Survival in Adherent Heart Transplant Patients in the Contemporary Era

Background

C4d immunostaining of surveillance endomyocardial biopsies (EMB) and testing for donor specific antibodies (DSA) are routinely performed in the first year of heart transplantation (HTx) in adult patients. C4d and DSA positivity have not been evaluated together with respect to clinical outcomes in the contemporary era (2010-current).

Methods

This was a single center, retrospective study of consecutive EMBs performed between November 2010 and April 2023. The primary objective was to determine whether history of C4d and/or DSA positivity could predict death, cardiac death, or retransplant. Secondary analyses included cardiac allograft dysfunction and cardiac allograft vasculopathy. Cox proportional hazards models were used for single predictor and multipredictor analyses.

Results

A total of 6,033 EMBs from 519 HTx patients were reviewed for the study. There was no significant difference (p = 0.110) in all-cause mortality or cardiac retransplant between four groups: C4d+/DSA+, C4d+/DSA-, C4d-/DSA+, and C4d-/DSA-. The risk for cardiac mortality or retransplant was significantly higher in C4d+/DSA+ versus C4d-/DSA- patients (HR = 4.73; pc = 0.042) but not significantly different in C4d+/DSA- versus C4d-/DSA- patients (pc = 1.000). Similarly, the risk for cardiac allograft dysfunction was significantly higher in C4d+/DSA+ versus C4d-/DSA- patients (HR 3.26; pc = 0.001) but not significantly different in C4d+/DSA- versus C4d-/DSA- patients (pc = 1.000). Accounting for nonadherence, C4d/DSA status continued to predict cardiac allograft dysfunction but no longer predicted cardiac death or retransplant.

Conclusions

Medically adherent C4d+/DSA+ HTx patients show significantly greater risk for cardiac allograft dysfunction but not cardiac mortality or retransplant. In contrast, C4d+/DSA- patients represent a new immunopathologic group with a clinical course similar to that of HTx patients without antibody mediated rejection.

Using complete blood count, serum immunoglobulins G/A/M and complement C3/C4 levels to predict the risk of COPD acute exacerbation: 2-year follow-up in a single-center prospective cohort study

Autoimmunity is present in patients with stable chronic obstructive pulmonary disease (COPD), playing a role in indirect and direct ways. We aimed to explore whether autoimmunity could play a role in COPD exacerbations and construct autoimmunity-related prediction models. This prospective, longitudinal, observational cohort study enrolled 155 patients with acute COPD exacerbations (AECOPD) followed for at least two years. The laboratory parameters, including complete blood count, serum immunoglobulins G/A/M and complement C3/C4 levels, were collected at enrollment. We studied the demographic characteristics, clinical characteristics and laboratory parameters to identify independent risk factors and build predictive models. The results showed that lower lymphocyte count was associated with noninvasive ventilation (NIV) in patients with AECOPD (the odds ratio [OR] 0.25, the 95% confidence interval [CI]: 0.08-0.81, P = 0.02). Lymphocyte count performed well with an area under the curves (AUC) of 0.75 (P < 0.0001, sensitivity: 78.1%, specificity: 62.3%, cutoff value [Cov] ≤ 1.1). The C index, calibration plot, decision curve analysis (DCA) and bootstrap repetitions indicated that this clinical prediction model based on lymphocyte count for NIV in patients with AECOPD performed well. Having prior home oxygen therapy (OR: 2.82, 95% CI: 1.25-6.36, P = 0.013) and higher COPD Assessment Test (CAT) scores (OR: 1.14, 95% CI: 1.03-1.25, P = 0.011) were associated with the increased risk for respiratory failure. For predicting respiratory failure, CAT scores and home oxygen therapy combined had an AUC-ROC of 0.73 (P < 0.0001). This clinical prediction model based on lymphocyte count may help to assist in treatment decisions for NIV in patients with AECOPD. Lower complement C3 seems to be associated with worse outcomes in patients with AECOPD.

Evaluation of serum complement C4 among COVID-19 patients in Khartoum state: a case control-based study

Background: The complement system is made up of an abundance of unique plasma proteins that play an important role in innate immunity and inflammation, aiding in the fight against pathogenic microbes and viral diseases. The purpose of this study was to evaluate the serum complement C4 concentration in COVID-19 patients in Khartoum and compare them to healthy controls. Methods: A total of 100 samples were collected, 50 samples from COVID-19 patients who presented as cases and 50 samples from people who were evidently healthy. Overall, 33 (66%) the patient populations in the case group were not in the hospital's intensive care unit (ICU), compared to 17 (34%) who were. The concentrations of C4 in each serum sample were calculated in milligrams per deciliter. SPSS version (20) was used to analyze the data. Results: The means level of complement C4 (mg/dL) were 37.44 ±18.618, 23.90 ±10.229 in the case group and in the control group, respectively. There was a statistically significant difference in complement C4 level between case and control (p-values ≤0.01). In addition, the mean complement C4 level in the ICU and non-ICU case groups was 25.00±17.85 and 43.85±15.712 mg/dL, respectively. There was a statistically significant variance in complement C4 level between ICU and non-ICU (p-values ≤0.01). Furthermore, the cases were divided into four age groups: 20-40, 40-60, 60-80, and over 80 years old. The one-way ANOVA test showed no statistically significant differences between age categories in complement C4 level (P = 0.735) Conclusions: The case group had a higher mean level of complement C4 than the control group, which could be understood by the stimulation of the complement cascade during the COVID-19 illness. Furthermore, the complement C4 level in severe COVID-19 patients was lower than in non-severe COVID-19.

Comparative analysis of complement C3 and C4 serum levels for outcome prediction in ANCA-associated renal vasculitis

BACKGROUND

The activation of the complement system contributes essentially to the pathogenesis of anti-neutrophil cytoplasmic antibody (ANCA)-associated renal vasculitis. We here aimed to directly compare levels of C3 and C4 for outcome prediction in ANCA-associated renal vasculitis.

METHODS

Serum levels of complement components C3 and C4 were directly compared in association with clinical and outcome data in a retrospective cohort of ANCA-associated renal vasculitis.

RESULTS

As compared to poor outcome prediction by low levels of complement C3 (p = 0.0093), low levels of complement C4 did not associate with early requirement of kidney replacement therapy (KRT) or death (p = 0.2396). In the subgroup that experienced KRT or death, low C3 levels identified 11/14 (78.6%, p = 0.0071) and C4 levels 9/14 (64.3%, p = 0.1786) cases. Interestingly, 2/14 (14.3%) patients that experienced KRT or death had isolated C4 lowering, and combining low C3 and/or C4 levels identified 13/14 (92.3%, p < 0.0001) cases in this subgroup. Non-superiority to predict poor outcome by low C3 and/or C4 as compared to C3 alone in the total cohort was attributed to 4/24 (16.7%) patients with isolated C4 lowering in the subgroup that did not experience KRT or death.

CONCLUSION

While low levels of complement C3 were superior in predicting poor outcome in ANCA-associated renal vasculitis, a minor fraction with poor outcome had isolated C4 lowering not captured by serum C3 measurements. Therefore, detailed knowledge of distinct complement components contributing to kidney injury could be of relevance to improve current strategies targeting the complement system in ANCA-associated renal vasculitis.

Relationship of selective complement markers with schizophrenia

Immune system dysregulation may be involved in schizophrenia, but biomarker studies have thus far reported inconsistent findings. The relationship of plasma levels of complement markers C3 and C4, with schizophrenia, sociodemographic and clinico-psychological factors were here studied in 183 patients and 212 controls. C3 and C4 levels were significantly higher in the patients and in subjects with elevated C-reactive protein (CRP), and positively correlated with body mass index (BMI) (p < 0.05). Schizophrenia, BMI, and CRP were significant predictors for C3 and C4 levels in multivariate analyses (p < 0.001). In conclusion, complements C3 and C4 are potential peripheral biomarkers in schizophrenia.

Purification of Human Complement Component C4 and Sample Preparation for Structural Biology Applications

Activated complement component C4 (C4b) is the nonenzymatic component of the classical pathway (CP) convertases of the complement system. Preparation of C4 and C4b samples suitable for structural biology studies is challenging due to low yields and complexity of recombinant C4 production protocols reported so far and heterogeneity of C4 in native sources. Here we present a purification protocol for human C4 and describe sample preparation methods for structural investigation of C4 and its complexes by crystallography, small angle X-ray scattering, and electron microscopy.

Complement C4A Regulates Autoreactive B Cells in Murine Lupus

Systemic lupus erythematosus (SLE) is a severe autoimmune disease mediated by pathogenic autoantibodies. While complement protein C4 is associated with SLE, its isoforms (C4A and C4B) are not equal in their impact. Despite being 99% homologous, genetic studies identified C4A as more protective than C4B. By generating gene-edited mouse strains expressing either human C4A or C4B and crossing these with the 564lgi lupus strain, we show that, overall, C4A-like 564Igi mice develop less humoral autoimmunity than C4B-like 564Igi mice. This includes a decrease in the number of GCs, autoreactive B cells, autoantibodies, and memory B cells. The higher efficiency of C4A in inducing self-antigen clearance is associated with the follicular exclusion of autoreactive B cells. These results explain how the C4A isoform is protective in lupus and suggest C4A as a possible replacement therapy in lupus.

Simoni et al. address a long-standing question about how complement C4A and C4B isoforms differ in function in vivo in autoimmunity. They find that C4A leads to an increased protection in humoral autoimmunity relative to C4B. Autoantibody diversity is likewise dependent on the C4 protein isotype.

Complement component C4-like protein in Atlantic cod (Gadus morhua L.) - Detection in ontogeny and identification of post-translational deimination in serum and extracellular vesicles

The complement system is a critical part of teleost immune defences, with complement component C4 forming part of the classical and lectin pathways. Cod C4-like protein was isolated from plasma, specific antibodies generated and C4-like protein was assessed in cod sera, mucus and in extracellular vesicles (EVs) from serum and mucus. Higher levels of C4-like protein were detected in serum- than mucus-derived EVs. Post-translational deimination, caused by conversion of arginine into citrulline, can affect protein structure and function. Here we detected deiminated forms of C4-like protein in cod serum and at lower levels in mucus. C4-like protein was also found in deiminated form at low levels in EVs from both serum and mucus. C4-like protein was assessed by immunohistochemistry in cod larvae and detected in a range of organs including in liver, kidney, gut, muscle, skin and mucus, as well as in neuronal tissues of the brain, spinal cord and eye. This abundance of C4-like protein during early development may indicate roles in tissue remodelling, in addition to immune defences. The presence of deiminated C4-like protein in serum and mucosa, as well as in EVs, may suggest C4 protein moonlighting via post-translational deimination.

Impact of C4, C4A and C4B gene copy number variation in the susceptibility, phenotype and progression of systemic lupus erythematosus

BACKGROUND

Complement component 4 (C4) gene copy number (GCN) affects the susceptibility to systemic lupus erythematosus (SLE) in different populations, however the possible phenotype significance remains to be determined. This study aimed to associate C4A, C4B and total C4 GCN and SLE, focusing on the clinical phenotype and disease progression.

METHODS

C4, C4A and C4B GCN were determined by real-time PCR in 427 SLE patients and 301 healthy controls, which underwent a detailed clinical evaluation according to a pre-established protocol.

RESULTS

The risk of developing SLE was 2.62 times higher in subjects with low total C4 GCN (< 4 copies, OR = 2.62, CI = 1.77 to 3.87, p < 0.001) and 3.59 times higher in subjects with low C4A GCN (< 2 copies; OR = 3.59, CI = 2.15 to 5.99, p < 0.001) compared to those subjects with normal or high GCN of total C4 (≥4) and C4A (≥2), respectively. An increased risk was also observed regarding low C4B GCN, albeit to a lesser degree (OR = 1.46, CI = 1.03 to 2.08, p = 0.03). Furthermore, subjects with low C4A GCN had higher permanent disease damage as assessed by the Systemic Lupus International Collaborating Clinics - Damage Index (SLICC-DI; median = 1.5, 95% CI = 1.2-1.9) than patients with normal or high copy number of C4A (median = 1.0, 95% CI = 0.8-1.1; p = 0.004). There was a negative association between low C4A GCN and serositis (p = 0.02) as well as between low C4B GCN and arthritis (p = 0.02).

CONCLUSIONS

This study confirms the association between low C4 GCN and SLE susceptibility, and originally demonstrates an association between low C4A GCN and disease severity.

Serum complement C4 is an important prognostic factor for IgA nephropathy: a retrospective study

Background

IgA nephropathy (IgAN) is the most common glomerulonephritis worldwide and is an important cause of end-stage renal disease (ESRD). Exploring novel biomarkers is necessary for predicting the disease activity and progression of IgAN patients. The present study sought to investigate the value of serum C4 for predicting the prognosis of IgAN patients.

Methods

The primary endpoint of this retrospective study was a composite event of either a ≥ 50% reduction in estimated glomerular filtration rate (eGFR) or end-stage renal disease (ESRD) or death. The associations between serum C4 and clinicopathological parameters and prognosis of this cohort of IgAN patients were evaluated.

Results

The present study included 1356 IgAN patients. Serum C4 levels correlated significantly with clinical prognostic factors. Serum C4 levels correlated positively with urinary protein excretion (r = 0.307, P < 0.001), and negatively correlated with estimated glomerular filtration rate (r = − 0.281, P < 0.001). Furthermore, serum C4 levels increased with aggravation of tubulointerstitial injury, crescents and ratios of global sclerosis (all P < 0.05). Prognostic analyses with the Cox proportional hazards regression model and Kaplan-Meier survival curves further identified serum C4 as an independent risk factor for the prognosis of IgAN.

Conclusions

The present study identified serum C4 as a useful predictor for the prognosis of IgAN patients. The mechanism of the trend of serum C4 in IgAN needs to be illustrated in further research.

Electronic supplementary material

The online version of this article (10.1186/s12882-019-1420-0) contains supplementary material, which is available to authorized users.

Deciphering microbiome and neuroactive immune gene interactions in schizophrenia

The body's microbiome represents an actively regulated network of novel mechanisms that potentially underlie the etiology and pathophysiology of a wide range of diseases. For complex brain disorders such as schizophrenia, understanding the cellular and molecular pathways that intersect the bidirectional gut-brain axis is anticipated to lead to new methods of treatment. The means by which the microbiome might differ across neuropsychiatric and neurological disorders are not known. Brain disorders as diverse as schizophrenia, major depression, Parkinson's disease and multiple sclerosis appear to share a common pathology of an imbalanced community of commensal microbiota, often measured in terms of a leaky gut phenotype accompanied by low level systemic inflammation. While environmental factors associated with these disease states might contribute to intestinal pathologies, products from a perturbed microbiome may also directly promote specific signs, symptoms and etiologies of individual disorders. We hypothesize that in schizophrenia, it is the putatively unique susceptibility related to genes that modulate the immune system and the gut-brain pleiotropy of these genes which leads to a particularly neuropathological response when challenged by a microbiome in dysbiosis. Consequences from exposure to this dysbiosis may occur during pre- or post-natal time periods and thus may interfere with normal neurodevelopment in those who are genetically predisposed. Here, we review the evidence from the literature which supports the idea that the intersection of the microbiome and immune gene susceptibility in schizophrenia is relevant etiologically and for disease progression. Figuring prominently at both ends of the gut-brain axis and at points in between are proteins encoded by genes found in the major histocompatibility complex (MHC), including select MHC as well as non-MHC complement pathway genes.

Insights on the relationship between complement component C4 serum concentrations and C4 gene copy numbers in a Western Australian systemic lupus erythematosus cohort

The relationship between serum concentration of complement C4 ([C4]) and C4 gene copy number (GCN) was investigated in 56 systemic lupus erythematosus (SLE) patients and 33 age and sex-matched controls in a Western Australian population. C4A and C4B gene copy numbers (C4A & B GCN) together with the presence or absence of the ≈6.4-kb human endogenous retroviral element type K (hereafter HERV-K) in intron 9 were estimated by two TaqMan™ real-time PCR (RT-PCR) assays that measured total C4 and HERV-K GCNs, respectively. There was good correlation between the two methods; however, the HERV-K GCN method showed a positive bias (≈6%) relative to the C4A & B total GCN. Despite individual variation, excellent correlation between total C4 GCN and mean [C4] per GCN was observed for both the SLE and control cohorts ( R²= 88% and R²= 99%, respectively). It was noted that serum [C4] was significantly lower in the SLE patients than the controls ( p = 0.006) despite there being no difference between C4A and C4B GCN in both cohorts. The data therefore confirm previous reports that the C4A genes are preferentially associated with the presence of the HERV-K insertion relative to C4B genes and does not support the hypothesis that low [C4] in SLE is explained by low C4A GCNs. There was no evidence also that the presence of the HERV-K insertion in C4 genes influenced [C4]. This study supports the view that low [C4] in SLE patients is due to consumption rather than deficient synthesis related to lower C4A & B GCN.

The Role of Immunological Factors on Sudden Sensoryneural Hearing Loss

INTRODUCTION

In this study, we examined the role of immunological factors on sudden sensory neural hearing loss (SSNHL).

MATERIALS AND METHODS

This prospective case-controlled study was performed in patients with SSNHL who referred to the ear, nose, and throat (ENT) ward. Fifty-six patients with SSNHLoccurring within a 72-hr period were selected as the case group and 56 participants who had no recent history of disease were assigned to the control group. Mean levels of immunological factors including erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), rheumatoid factor (RF), antinuclear antibody (ANA), anti-neutrophil cytoplasmic antibody (ANCA) (C, P), anti-cyclic citrullinated peptide (anti-CCP), DSM, hemoglobin (Hb), complement component 3 (C3), and complement component 4 (C4) were evaluated in the blood samples in each group.

RESULTS

There were 31 male and 25 female participants in the control group, while the case group had 26 male and 30 female participants. The mean age of the participants was 36.2 ± 13.4 years in the control group and 40.80 ± 13.37 years in the case group. The two groups differed significantly in terms of mean ESR, ANA, C3, C4 and monocytes, with higher levels in the case group (P<0.05). However, differences in mean CRP, anti-Ds DNA, Hb, anti-CCP, white blood cells (WBC), neutrophils, lymphocytes, eosinophils, and platelets were not statistically significant between the case and control groups (P>0.05).

CONCLUSION

Because some of the immunological factors investigated in this study were significantly higher in patients with SSNHL, it can be concluded that there is an association between these immunological factors and SSNHL. Further studies are recommended to accurately determine the effect of these factors on the development of SSNHL and its treatment.

[Comparison of age-based clinical and abnormal immune parameters in patients with Henoch-Schönlein purpura]

Objective: To explore age-based clinical and immune parameters in Henoch-Schönlein purpura (HSP) to determine clinically useful markers reflecting disease characteristic. Methods: A cohort of 502 patients with HSP were enrolled into this retrospective study to evaluate their clinical and immune data. Results: Majority HSP cases occurred at age ≤14 years and showed significant immune imbalances of ESR, CD3(+) cells, CD4(+) cells, CD3(-)CD16(+)CD56(+) cells, CD4(+)/CD8(+) cells, IgG, IgA, IgM, IgE, complements C3/C4 and ASO in the acute phase. Compared to patients aged >14 years, symptoms of joint were more frequent at disease onset in patients aged ≤14 years (20.8% vs 7.6%, χ(2)=13.547, P<0.001) , and involvement of digestive tract and joint were also more frequent (57.4% vs 33.8%, χ(2)=24.106, P<0.001; 55.9% vs 32.5%, χ(2)=23.768, P<0.001, respectively) , but not for involvement of kidney (21.4% vs 51.3%, χ(2)=42.440, P<0.001) . The patients aged ≤14 years had distinct immune state, reductions of CD3(+) cells, CD4(+) cells and IgG were more frequent than patients aged >14 years, also increase of ASO (33.1% vs 20.0%, χ(2)=6.656, P=0.010) , but not increase of IgA (2.6% vs 39.4%, χ(2)=15.582, P<0.001) . In addition, reduction of IgG and increase of IgE were positively associated with digestive tract involvement (P<0.001, P=0.001, respectively) , reduction of CD3(+)CD4(+) cells and normal IgM were positively associated with joint involvement (P=0.004, P=0.003, respectively) , increase of CD3(+)CD8(+) cells and normal CD3(+) cells were positively associated with kidney involvement (P=0.032, P=0.014, respectively) . Conclusion: HSP showed significant immune imbalance in the acute phase, patients between aged ≤14 and >14 years had distinct clinical and immune characteristic, and abnormal immune parameters were significantly associated with organ involvements.

Anti-C1q Antibody is Associated with Renal and Cutaneous Manifestations in Asian Indian Patients with Systemic Lupus Erythematosus

INTRODUCTION

C1q play an important role in clearance of immune complexes and apoptotic cell debris. Impaired clearance leads to exposure of C1 native antigen and development of anti-C1q antibody formation. Anti-C1q antibody is well studied in Systemic Lupus Erythematosus (SLE). Significance of anti-C1q Ab in Indian SLE patients and their clinical manifestations is not clear.

AIM

The aim of this study was to investigate associations between anti-C1q antibody and clinical as well as serological markers of SLE.

MATERIALS AND METHODS

Retrospective study of SLE patients fulfilling either American College of Rheumatology (ACR) 1990 or Systemic Lupus International Collaborating Clinics (SLICC) 2012 classification criteria were recruited from inpatients and outpatients services of the Clinical immunology and Rheumatology Department, Christian Medical College at Vellore, India between March 2013 and January 2015. Anti-C1q antibody was assayed by ELISA (Demeditec Diagnostics GmbH, Germany). Logistic regression analysis was performed to find the association of anti-C1q antibodies with serological and clinical parameters in SLE including Lupus Nephritis (LN).

RESULTS

Sixty nine patients (54.76%) out of 126 SLE patients had LN. Anti-C1q levels were higher in patients with LN as compared to those without (p<0.05). Anti-C1q antibody was also significantly associated with positive C1q immunofluorescence staining in renal biopsy specimens (p<0.05). Overall, renal Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) {OR 1.35 (1.08-1.69)}, low C4 {OR 3.11 (1.04-9.26)} and mucocutaneous manifestation {OR 4.72 (1.38-16.05)} were independently associated with anti-C1q levels in serum.

CONCLUSION

Renal SLEDAI, low C4 and mucocutaneous manifestations were independently associated with raised anti C1q antibody in SLE patients.

Clinical characteristics and real-life diagnostic approaches in all Danish children with hereditary angioedema

Background

With a potentially early onset, hereditary angioedema (HAE) requires special knowledge also in infancy and early childhood. In children from families with HAE, the diagnosis should be confirmed or refuted early, which can be difficult. Studies of childhood HAE and the diagnostic approaches are limited. Our aim was to investigate the entire Danish cohort of children with HAE and non-HAE children of HAE patients for diagnostic approaches and clinical characteristics.

Results

We included 41 children: 22 with HAE and 19 non-HAE. Of the HAE children, 14 were symptomatic—median age at onset was 4 [1–11] years. The first attack was peripheral in 8/14 children and abdominal in 6/14 children, i.e. no one had their first attacks in the upper airways. Most children had less than one attack per month. All of the symptomatic children had been treated with tranexamic acid and/or C1 inhibitor concentrate. Unlike in other countries, androgens were not used in our pediatric cohort. Home therapy with C1 inhibitor concentrate was established in 9 cases: 6 children were trained in self-administration and 3 children were treated by parents. Of the children, 10 had been diagnosed by symptoms, including 3 without family history—median age of diagnosis among these children was 5.35 [2–13.2] years. In 31 children, HAE was diagnosed or refuted before symptoms by blood samples. In 23 of these children, complement values were investigated, and in 9 cases genetic testing was added to the complement measurements. In 8 children recently investigated, genetic testing was first choice. Cord blood was used for complement measurements in 9 children and for genetic testing in 4 children. Results of complement measurements were equivocal in several cases, especially in the cord blood samples, and the sensitivity of low complement C4 for the diagnosis of HAE was 75%.

Conclusions

We investigated clinical characteristics in all Danish children with HAE. The rate of home therapy was high and androgens had been avoided. Complement values were often equivocal, especially in cord blood samples. Consequently, we have changed diagnostic practice to early genetic testing in children where the family mutation is known.

Evolutionary analysis of two complement C4 genes: Ancient duplication and conservation during jawed vertebrate evolution

The complement C4 is a thioester-containing protein, and a histidine (H) residue catalyzes the cleavage of the thioester to allow covalent binding to carbohydrates on target cells. Some mammalian and teleost species possess an additional isotype where the catalytic H is replaced by an aspartic acid (D), which binds preferentially to proteins. We found the two C4 isotypes in many other jawed vertebrates, including sharks and birds/reptiles. Phylogenetic analysis suggested that C4 gene duplication occurred in the early days of the jawed vertebrate evolution. The D-type C4 of bony fish except for mammals formed a cluster, termed D-lineage. The D-lineage genes were located in a syntenic region outside MHC, and evolved conservatively. Mammals lost the D-lineage before speciation, but D-type C4 was regenerated by recent gene duplication in some mammalian species or groups. Dual C4 molecules with different substrate specificities would have contributed to development of the antibody-dependent classical pathway.

Complement C4 induces regulatory T cells differentiation through dendritic cell in systemic lupus erythematosus

Background

Systemic lupus erythematosus (SLE) is a prototypic systemic autoimmune disease. Complement component 4 (C4) has be proved to play a role in pathogenesis of SLE. In the present study, we investigated the effect of C4 on T cells differentiation.

Methods

Thirty SLE patients were included in this study. CD4+ T cells were isolated from healthy subjects, and dendritic cells (DCs) were isolated from healthy subjects or SLE patients. C4 was supplemented to co-incubate with T cells and DCs.

Results

Serum C4 concentration was positively correlated with regulatory T cell (Treg) percentage (R² = 0.5907, p < 0.001) and TGFβ concentration (R² = 0.5641, p < 0.001) in SLE patients. Different concentrations of C4 had no effect on T cells differentiation. Co-incubated T cells with DCs and C4 for 7 days, the Treg percentage and TGF-β concentration were significantly elevated. In addition, pre-treated DCs (from healthy subjects or SLE patients) with C4 and then co-incubated with T cells, the increases of Treg percentage and TGF-β concentration were also observed.

Conclusion

C4 takes part in T cells differentiation to Treg cells via DCs.

Serum complements C3 and C4 in chronic HCV infection and their correlation with response to pegylated interferon and ribavirin treatment

BACKGROUND AND STUDY AIMS

To search for an immunological parameter that may correlate with the response to interferon (IFN) treatment is very crucial. The objective of this study was to correlate the levels of C3 and C4 complement components with the response to IFN treatment in patients with chronic hepatitis C virus (HCV) infection.

PATIENTS AND METHODS

This study was conducted on 100 patients and control subjects classified into three groups. Group (I) consisted of 50 patients with chronic hepatitis C who were receiving IFN treatment and showed various responses; group (II) included 25 patients with chronic hepatitis C naive to IFN treatment; and group (III) included 25 healthy subjects matched for age and sex who served as controls. Measurement of the level of complement C3 and C4 was done by a quantitative turbidimetric test. Measurement of complement levels in group (I) was done at the end of treatment at the 48th week.

RESULTS

Serum levels of C3 and C4 were found to be significantly reduced in all patients with chronic HCV infection in both groups (I and II) compared to the healthy control group (III) (p<0.05). Moreover, chronic HCV patients treated with IFN and ribavirin had significantly lower levels of C3 and C4 compared with patients naive to IFN and ribavirin treatment. At the end of treatment, both C3 and C4 had significantly increased in responders to IFN when compared to non-responders (p=0.025 and 0.05, respectively). There was a significant negative correlation between C3 and C4 levels and the concentration of serum alanine aminotransferase (ALT) measured simultaneously.

CONCLUSION

Higher C3 and C4 serum concentrations were found to be positively correlated to the end-of-treatment response in patients with chronic HCV infection treated with IFN and ribavirin.