Complement component C4 levels in the cerebrospinal fluid and plasma of patients with schizophrenia.

Abnormalities in the complement system have been described in patients with schizophrenia, with those individuals having greater frequency of complement component 4A (C4A) alleles and higher C4A transcript levels in postmortem brain tissue. Importantly, abnormalities in C4A and other complement molecules have been associated with synaptic pruning abnormalities that occur during neurodevelopment. A few studies have investigated C4 levels in living patients with schizophrenia, but all of them did so using peripheral blood samples. No studies have examined C4 levels in cerebrospinal fluid (CSF), presumably a better biofluid choice given its intimate contact with the brain. Therefore, we report for the first time on C4 levels in CSF and plasma of patients with schizophrenia. In this study, we obtained CSF in 32 patients with schizophrenia spectrum disorders and 32 healthy volunteers and peripheral blood samples in 33 SSD and 31 healthy volunteers. C4 levels were measured using Abcam ELISA assays. Univariate analysis did not show a statistically significant difference in CSF C4 values between groups. However, a multivariable analysis showed a statistically significant increase in CSF C4 levels between groups after adjusting for sex and age. We also observed a high correlation between CSF C4 levels and age. By contrast, plasma C4 levels were not significantly different between groups. CSF and plasma C4 levels were not significantly correlated. Therefore, the use of CSF samples is critical and should be complementary to the use of peripheral blood samples to allow for a comprehensive understanding of complement C4 abnormalities in schizophrenia.

Complement genes contribute sex-biased vulnerability in diverse disorders.

Many common illnesses, for reasons that have not been identified, differentially affect men and women. For instance, the autoimmune diseases systemic lupus erythematosus (SLE) and Sjögren's syndrome affect nine times more women than men1, whereas schizophrenia affects men with greater frequency and severity relative to women2. All three illnesses have their strongest common genetic associations in the major histocompatibility complex (MHC) locus, an association that in SLE and Sjögren's syndrome has long been thought to arise from alleles of the human leukocyte antigen (HLA) genes at that locus3-6. Here we show that variation of the complement component 4 (C4) genes C4A and C4B, which are also at the MHC locus and have been linked to increased risk for schizophrenia7, generates 7-fold variation in risk for SLE and 16-fold variation in risk for Sjögren's syndrome among individuals with common C4 genotypes, with C4A protecting more strongly than C4B in both illnesses. The same alleles that increase risk for schizophrenia greatly reduce risk for SLE and Sjögren's syndrome. In all three illnesses, C4 alleles act more strongly in men than in women: common combinations of C4A and C4B generated 14-fold variation in risk for SLE, 31-fold variation in risk for Sjögren's syndrome, and 1.7-fold variation in schizophrenia risk among men (versus 6-fold, 15-fold and 1.26-fold variation in risk among women, respectively). At a protein level, both C4 and its effector C3 were present at higher levels in cerebrospinal fluid and plasma8,9 in men than in women among adults aged between 20 and 50 years, corresponding to the ages of differential disease vulnerability. Sex differences in complement protein levels may help to explain the more potent effects of C4 alleles in men, women's greater risk of SLE and Sjögren's syndrome and men's greater vulnerability to schizophrenia. These results implicate the complement system as a source of sexual dimorphism in vulnerability to diverse illnesses.

Cerebrospinal fluid levels of complement proteins C3, C4 and CR1 in Alzheimer's disease.

Alzheimer's disease (AD) is strongly associated with loss of synapses. The complement system has been shown to be involved in synaptic elimination. Several studies point to an association between AD and the complement system. The purpose of this study was to examine the association of cerebrospinal fluid (CSF) levels of complement components 3 and 4 (C3 and C4, respectively), and complement receptor 1 (CR1) with AD in 43 patients with AD plus dementia, 42 patients with mild cognitive impairment (MCI) who progressed to AD during follow-up (MCI-AD), 42 patients with stable MCI and 44 controls. Complement levels were also applied in a multivariate model to determine if they provided any added value to the core AD biomarkers Aß42, T-tau and P-tau. We found elevated CSF levels of C3 and C4 in AD compared with MCI without progression to AD, and elevated CSF levels of CR1 in MCI-AD and AD when these groups were merged. These results provide support for aberrant complement regulation as a part in the AD process, but the changes are not diagnostically useful.

A novel peptidomics approach to detect markers of Alzheimer's disease in cerebrospinal fluid.

Sensitive and specific diagnosis and monitoring of disease progression are of prime importance to develop new therapies for Alzheimer's disease patients. Although the diagnostic accuracy, verified by pathological examination is high, it is currently not possible to diagnose Alzheimer's disease with a high degree of certainty until relatively late in the disease process. Here, we have undertaken a peptidome analysis of postmortem cerebrospinal fluid of neuropathologically confirmed Alzheimer's disease patients and non-demented controls using a combination of methods and technologies. This includes novel sample preparation based on the enrichment of endogenous, proteolytically derived peptides as well as peptides non-covalently bound to abundant proteins. We observed differences in peptide profiles associated with Alzheimer's disease in the endogenous peptide fraction and in the protein-bound peptide fraction. The discriminating peptides in the unbound peptide fraction were identified as VGF nerve growth factor inducible precursor, and complement C4 precursor, whereas the discriminating peptides in the protein-bound fraction were identified as VGF nerve growth factor inducible precursor, and alpha-2-HS-glycoprotein.

Reibergram of intrathecal synthesis of C4 in patients with eosinophilic meningitis caused by Angiostrongylus cantonensis.

Angiostrongylus cantonensis produces eosinophilic meningitis in humans and is endemic in Thailand, Taiwan, China, and the Caribbean region. During infection with this parasite, it is important to know if the complement system may be activated by the classical or lectin pathway. Cerebrospinal fluid and serum samples from 20 patients with meningitic angiostrongyliasis were used to quantify C4 levels and albumin. Results were plotted on a C4 CSF/serum quotient diagram or Reibergram. Twelve patients showed intrathecal synthesis of C4. Antibody-dependent complement cytotoxicity should be considered as a possible mechanism that destroys third-stage larvae of this helminth in cerebrospinal fluid of affected patients.

Intrathecal synthesis of complement components C3c and C4 in the central nervous system infections with signs of the acute serous meningitis syndrome.

Two hundred and ten patients with meningismus and the infections of the central nervous system (CNS) with the clinical symptoms and signs of the acute serous meningitis syndrome, were divided in to groups according to etiology (enterovirus meningitis-ENTERO, serous meningitis various etiology-SM and tuberculous meningitis-TBC). Intrathecal synthesis (ITS) of C3c and C4 complement components and IgG were determined by the method of cerebrospinal indexes (I), to examine their role in differential diagnosis of this syndrome. Correlative study between the CSF/serum ratio (Q) for albumin (Alb) and QC3c and QC4 in patients with no proven ITS of this two complement proteins, and the comparative study of the increased value of C3cI and C4I (and IgGI) between the examined groups of the patients was done. Highly significant correlations were found between QAlb and QC3c (r = 0.89, p < 0.001) and QC4 (r = 0.85, p < 0.001). In 22.4% of the examined patients ITS of C3c and C4 were found. There was no difference in frequency of ITS of the two complement proteins between the examined groups, nor inside any particular group. TBC group had significantly lower (p < 0.05) intensity of ITS of C3c and C4 than MNG and ENTERO, and significantly higher intensity of ITS of IgG (p < 0.05) than the other tested groups. CSF index was confirmed as a valid method to detect intrathecal C3c and C4 production. Determination of ITS C3c and C4 could not be of great help in differential diagnosis in the acute serous meningitis syndrome. The intensity of ITS of C3c and C4, related to the intensity of ITS of IgG, could be of help in the determination of the duration of the disease.

Activation of complement and contact system in Alzheimer's disease.

beta-Amyloid protein (betaA) has been implicated in the pathogenesis of Alzheimer's disease (AD) because of its neurotoxicity and ability to trigger a local inflammatory response. Although assembly of betaA in particular aggregates seems to be crucial event in AD pathogenesis, soluble, non-fibrillar betaA may also be involved. Non-fibrillar betaA1-42, and truncated peptide 1-28, induced dose-dependent activation of C4 sparing C3. The mechanism of C4 activation was not dependent on C1q, because non-fibrillar betaA can still activate C4 in plasma genetically deficient in C1q. A C1q independent mechanism of complement classical pathway activation could be via the activation of contact/kinin system. The possible involvement of contact system in AD is suggested by the finding that this system is massively activated in CSF of AD patients. The mechanism of activation of contact system could be the result of an anionic interaction of residues within the region 1-11 of betaA1-42 with factor XII, and of kallikrein generation. Concomitant incubation of a small cationic peptide (lysine4) with betaA abrogated its ability to trigger the cleavage of high molecular weight kininogen. In vivo, prevention of contact system activation beside the reduction of kallikrein generation, can also decrease the activation of complement system and the release of interleukin-6, both factors being considered to play an important role in the inflammatory reactions in AD brain.

Cerebrospinal fluid C3 and C4 indexes in immunological disorders of the central nervous system.

OBJECTIVES: Validation of cerebrospinal fluid (CSF) indexes as a measure for intrathecal C3 and C4 production. Examination of their role in differential diagnosis of immunological disorders of the central nervous system (CNS). MATERIAL AND METHODS: Correlative study in controls (low back pain without disk herniation) between the CSF/serum ratio (Q) for albumin, and Q C3 and Q C4. Comparative study of C3 and C4 indexes in patients with CNS dysfunction due to relapsing-remitting (RR) multiple sclerosis (MS), secondary progressive (SP) MS, systemic lupus erythematosus (SLE), and human immunodeficiency virus (HIV) infection. RESULTS: Strong and statistically highly significant correlations between Q albumin and Q C3 (r=0.89, P=0.0001), and Q C4 (r=0.68, P= 0.0001). In MS patients decreased mean values for serum (RR, SP) and CSF (RR) C3, and increased C3 index mean value (RR, SP). In CNS SLE increase of mean C3 and C4 index values. In CNS HIV increase of mean C3 and C4 index values, and CSF C3 and C4 concentrations. Most individual index values were within the reference range. CONCLUSION: CSF index is a valid tool to detect intrathecal C3 or C4 production. C3 or C4 index contributes little to the differential diagnosis of immunological CNS disorders. C3 might play a pathogenic role in various immunological CNS disorders.

Increased CSF C4d in demyelinating neuropathy indicates the radicular involvement.

Plasma and cerebrospinal fluid (CSF) levels of C4d and the circulating immune complex (CIC) to C1q were measured in 12 patients with chronic inflammatory demyelinating polyneuropathy and Guillain-Barré syndrome. CSF C4d values more than 2 SD from the mean of 8 cervical spongylosis cases were demonstrated in the patients with proximal demyelination. The CSF C4d probably originated from both intrathecal synthesis and the systemic circulation. CSF levels of C4d may serve as a sensitive indicator for the radicular involvement in demyelinating polyneuropathy.

Increased concentration of C4d complement protein in CSF in amyotrophic lateral sclerosis.

Plasma and CSF concentrations of C4d and the circulating immune complex to C1q were measured in 27 patients with amyotrophic lateral sclerosis (ALS) or cervical spondylosis. There was no significant difference among groups in plasma C4d or in plasma or CSF concentrations of the circulating immune complex to C1q. The ALS group, however, had a significantly higher CSF concentration of C4d than the group with cervical spondylosis, as well as a higher C4d index (CSF to plasma C4d ratio x serum to CSF albumin ratio). These results suggest that augmented complement activation in the CNS occurs in ALS. Increased CSF concentration of C4d or raised C4d index may serve as a basis for differentiating ALS from cervical spondylosis.

Increased concentration of C4d complement protein in the cerebrospinal fluids in progressive supranuclear palsy.

Plasma and CSF levels of C4d and the circulating immune complex (CIC) to C1q were measured in 27 patients with progressive supranuclear palsy (PSP), Parkinson's disease (PD) and cervical spondylosis (CS). There was no significant difference among groups in plasma C4d or in plasma or CSF CIC to C1q. However, the PSP group had significantly higher CSF levels of C4d than the PD and CS groups. Higher CSF C4d index in the PSP group was also shown compared with PD and CS groups. These results suggest that augmented complement activation in the wide areas of the central nervous system occurs in PSP. CSF levels of C4d or C4d index may serve as a basis for differentiating PSP from PD.

Serum and CSF immunological findings in ALS.

Serum and CSF immunological findings were analysed in 37 patients with amyotrophic lateral sclerosis (ALS). ALS patients had significantly higher mean values of serum IgG and complement component C4 and significantly lower mean value of total haemolytic titre of complement (THC) compared with normal controls. Incidence of immune complexes (ICs) was significantly higher in sera of ALS patients than in normal controls. There was no significant difference regarding mean serum levels of IgM, IgA, and complement components C3 and Factor B between patients and controls. The blood-brain barrier (BBB) damage was found in 46% of patients. Intrathecal IgG synthesis was detected in six patients (16%). These results support the hypothesis of immune system involvement in ALS.

Diffuse CNS involvement in systemic lupus erythematosus: intrathecal synthesis of the 4th component of complement.

In extracerebral systemic lupus erythematosus (SLE), the complement system plays a prominent pathogenic role, and decreased serum concentration of the 4th component (C4) is a reliable indicator of systemic disease activity. In diffuse CNS-SLE, however, the pathogenic role of complement is less clear. In 12 patients with active diffuse CNS-SLE presenting with delirium (4), organic personality syndrome (3), or generalized seizures (5), we determined the CSF indexes of the complement components C3, C4, and factor B, and of IgG, IgA, and IgM. There was a significant increase of the C4 index in these patients compared with controls and a significantly higher CSF C4 index in patients with an increased IgM index. We conclude that intrathecal C4 is being produced in diffuse CNS-SLE.

Humoral immune response in patients with cerebral parenchymal cysticercosis treated with praziquantel.

The humoral immune response to treatment with praziquantel (PZQ) was studied in eight patients with parenchymal cerebral cysticercosis (CC). In the serum and in the cerebrospinal fluid (CSF) before, during and after the administration of the drug, the following were quantitated (a) levels of specific anticysticercous antibodies measured in optical densities by the ELISA method; (b) levels of IgG, IgM, IgA and IgE; (c) levels of complement fraction C3, C4; (d) presence of immune complexes; (e) total number of white blood cells in the CSF. It was found that after treatment with PZQ, the level of specific anticysticercous antibodies and the level of IgG rose significantly in the CSF but not in the blood. The levels of the fractions of the complement and the immunoglobulins IgM, IgA and IgE did not change significantly either in the serum or in the CSF. The blood-brain barrier was found ruptured in three patients before therapy and in five patients after the therapy as measured by the albumin index. Nevertheless, the IgG index showed that there was local production of IgG in five patients before treatment and in seven after the end of it. The relative specific antibody index was greater than 1.0 in five patients before therapy and in seven after therapy. This data strongly supports the idea that the specific antibodies are produced intrathecally and are not derived from the serum pool through a ruptured blood-brain barrier. It was concluded that patients with parenchymal CC have an elevation of specific anticysticercous probably due to a combination of a ruptured blood-brain barrier and intrathecal synthesis. The relatively small rupture of the blood-brain barrier and the high IgG and relative specific antibody index suggest that intrathecal synthesis is the most important mechanism. The humoral immune response may be of importance not only in the elimination of the parasite but also in the genesis of the illness.

Association of Guillain-Barré syndrome and Henoch-Schönlein purpura: is immunoglobulin a responsible for the neurologic syndrome?

Guillain-Barré syndrome and Henoch-Schönlein purpura (HSP) appeared simultaneously in a 35-year-old woman. During the course of the Guillain-Barré syndrome, the presence of IgA aggregates and a decrease in complement components were noted in the cerebrospinal fluid. These abnormalities disappeared when the neurologic syndrome remitted. This suggests the responsibility of IgA immune complexes, characteristic of HSP, in the occurrence of the associated Guillain-Barré syndrome.

High levels of C3c in the cerebrospinal fluid from amyotrophic lateral sclerosis patients.

A study of several parameters of the humoral immunity in the serum and the cerebrospinal fluid (CSF) of thirteen Amyotrophic Lateral Sclerosis (ALS) patients was carried out. A significant increase in CSF C3c was shown. This feature was found to be significantly correlated to the CSF albumin/serum albumin ration (r = 0.70; p less than 0.05) and to the total CSF proteins (r = 0.86; p less than 0.01). The possible effect of the blood-brain barrier breakdown on the CSF complement levels was evaluated. On the basis of the recently found biochemical changes in ALS cell membranes it is proposed that the high levels of the CSF C3c may also be due to a defective binding to the lymphocytes C3 receptors.

The determination of the complement components C1q, C4 and C3 in serum and cerebrospinal fluid by radioimmunoassay.

Non-competitive 2-site radioimmunoassays (RIA) for the determination of the complement proteins C1q, C4 and C3 in cerebrospinal fluid (CSF) are described. The quantitative results of the RIAs were the same as those obtained by other assay methods: radial immunodiffusion and turbidimetry and, in the case of C4, the haemolytic assay. The concentrations of the complement proteins in paired CSF and serum samples from a group of 60 patients were measured, as well as those of albumin and IgG. The ratios (concentration in CSF)/(concentration in serum) of the complement proteins correlated poorly with that of albumin. In contrast, the ratio of IgG was significantly correlated with that of albumin. The ratios of the complement proteins were higher than might be expected on the basis of their molecular masses. This suggests that these proteins may be synthesized within the normal central nervous system.