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

Immunology of amyotrophic lateral sclerosis - role of the innate and adaptive immunity

This review aims to summarize the latest evidence about the role of innate and adaptive immunity in Amyotrophic Lateral Sclerosis (ALS). ALS is a devastating neurodegenerative disease affecting upper and lower motor neurons, which involves essential cells of the immune system that play a basic role in innate or adaptive immunity, that can be neurotoxic or neuroprotective for neurons. However, distinguishing between the sole neurotoxic or neuroprotective function of certain cells such as astrocytes can be challenging due to intricate nature of these cells, the complexity of the microenvironment and the contextual factors. In this review, in regard to innate immunity we focus on the involvement of monocytes/macrophages, microglia, the complement, NK cells, neutrophils, mast cells, and astrocytes, while regarding adaptive immunity, in addition to humoral immunity the most important features and roles of T and B cells are highlighted, specifically different subsets of CD4+ as well as CD8+ T cells. The role of autoantibodies and cytokines is also discussed in distinct sections of this review.

Evaluation of Peripheral Immune Activation in Amyotrophic Lateral Sclerosis

Accumulating evidence has revealed that immunity plays an important role in amyotrophic lateral sclerosis (ALS) progression. However, the results regarding the serum levels of immunoglobulin and complement are inconsistent in patients with ALS. Although immune dysfunctions have also been reported in patients with other neurodegenerative diseases, few studies have explored whether immune dysfunction in ALS is similar to that in other neurodegenerative diseases. Therefore, we performed this study to address these gaps. In the present study, serum levels of immunoglobulin and complement were measured in 245 patients with ALS, 65 patients with multiple system atrophy (MSA), 60 patients with Parkinson's disease (PD), and 82 healthy controls (HCs). Multiple comparisons revealed that no significant differences existed between patients with ALS and other neurodegenerative diseases in immunoglobulin and complement levels. Meta-analysis based on data from our cohort and eight published articles was performed to evaluate the serum immunoglobulin and complement between patients with ALS and HCs. The pooled results showed that patients with ALS had higher C4 levels than HCs. In addition, we found that the IgG levels were lower in early-onset ALS patients than in late-onset ALS patients and HCs, and the correlations between age at onset of ALS and IgG or IgA levels were significant positive. In conclusion, our data supplement existing literature on understanding the role of peripheral immunity in ALS.

Complement Profiles in Patients with Amyotrophic Lateral Sclerosis: A Prospective Observational Cohort Study

Background

The complement system has been suggested to be involved in the pathophysiology of amyotrophic lateral sclerosis (ALS), a progressive motor neuron disease. In the present study, we compared levels of selected complement markers to clinical outcome in ALS patients.

Methods

This observational, explorative cohort study included 92 ALS patients, 61 neurological controls (NCs) admitted for suspected aneurysmal subarachnoid haemorrhage, and 96 neurologically healthy controls (NHCs). Peripheral blood and cerebrospinal fluid (CSF) were obtained for the measurement of ficolin-1, −2, and −3; collectin-11, MBL, MASP-3, MAP-1, C4, C3, PTX-3, and complement activation products C4c, C3bc, and sC5b-9. We recorded clinical outcomes of ALS patients for 24 to 48 months after inclusion in order to analyse the effects of the complement markers on survival time.

Results

Compared with both control groups, ALS patients exhibited increased collectin-11, C4 and sC5b-9 in plasma, as well as increased ficolin-3 in CSF. Ficolin-2 was significantly decreased in plasma of the ALS patients compared with NHCs, but not with NCs. The concentration of collectin-11, C3 and C3bc correlated negatively with the revised ALS functional rating scale (ALSFRS-R). No association was found between levels of complement markers and survival as estimated by hazard ratios.

Conclusion

ALS patients exhibit aberrant expression of selected mediators of the lectin complement pathway as well as increased activation of the terminal complement pathway, corroborating the notion that the complement system might be involved in the pathophysiology of ALS.

An Ultrahigh-Affinity Complement C4b-Specific Nanobody Inhibits In Vivo Assembly of the Classical Pathway Proconvertase

The classical and lectin pathways of the complement system are important for the elimination of pathogens and apoptotic cells and stimulation of the adaptive immune system. Upon activation of these pathways, complement component C4 is proteolytically cleaved, and the major product C4b is deposited on the activator, enabling assembly of a C3 convertase and downstream alternative pathway amplification. Although excessive activation of the lectin and classical pathways contributes to multiple autoimmune and inflammatory diseases and overexpression of a C4 isoform has recently been linked to schizophrenia, a C4 inhibitor and structural characterization of the convertase formed by C4b is lacking. In this study, we present the nanobody hC4Nb8 that binds with picomolar affinity to human C4b and potently inhibits in vitro complement C3 deposition through the classical and lectin pathways in human serum and in mouse serum. The crystal structure of the C4b:hC4Nb8 complex and a three-dimensional reconstruction of the C4bC2 proconvertase obtained by electron microscopy together rationalize how hC4Nb8 prevents proconvertase assembly through recognition of a neoepitope exposed in C4b and reveals a unique C2 conformation compared with the alternative pathway proconvertase. On human induced pluripotent stem cell-derived neurons, the nanobody prevents C3 deposition through the classical pathway. Furthermore, hC4Nb8 inhibits the classical pathway-mediated immune complex delivery to follicular dendritic cells in vivo. The hC4Nb8 represents a novel ultrahigh-affinity inhibitor of the classical and lectin pathways of the complement cascade under both in vitro and in vivo conditions.

Innate Immunity: A Common Denominator between Neurodegenerative and Neuropsychiatric Diseases

The intricate relationships between innate immunity and brain diseases raise increased interest across the wide spectrum of neurodegenerative and neuropsychiatric disorders. Barriers, such as the blood–brain barrier, and innate immunity cells such as microglia, astrocytes, macrophages, and mast cells are involved in triggering disease events in these groups, through the action of many different cytokines. Chronic inflammation can lead to dysfunctions in large-scale brain networks. Neurodegenerative diseases, such as Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, amyotrophic lateral sclerosis, and frontotemporal dementia, are associated with a substrate of dysregulated immune responses that impair the central nervous system balance. Recent evidence suggests that similar phenomena are involved in psychiatric diseases, such as depression, schizophrenia, autism spectrum disorders, and post-traumatic stress disorder. The present review summarizes and discusses the main evidence linking the innate immunological response in neurodegenerative and psychiatric diseases, thus providing insights into how the responses of innate immunity represent a common denominator between diseases belonging to the neurological and psychiatric sphere. Improved knowledge of such immunological aspects could provide the framework for the future development of new diagnostic and therapeutic approaches.

Complement dysregulation in the central nervous system during development and disease

The complement cascade is an important arm of the immune system that plays a key role in protecting the central nervous system (CNS) from infection. Recently, it has also become clear that complement proteins have fundamental roles in the developing and aging CNS that are distinct from their roles in immunity. During neurodevelopment, complement signalling is involved in diverse processes including neural tube closure, neural progenitor proliferation and differentiation, neuronal migration, and synaptic pruning. In acute neurotrauma and ischamic brain injury, complement drives inflammation and neuronal death, but also neuroprotection and regeneration. In diseases of the aging CNS including dementias and motor neuron disease, chronic complement activation is associated with glial activation, and synapse and neuron loss. Proper regulation of complement is thus essential to allow for an appropriately developed CNS and prevention of excessive damage following neurotrauma or during neurodegeneration. This review provides a comprehensive overview of the evidence for functional roles of complement in brain formation, and its dysregulation during acute and chronic disease. We also provide working models for how complement can lead to neurodevelopmental disorders such as schizophrenia and autism, and either protect, or propagate neurodegenerative diseases including Alzheimer's disease and amyotrophic lateral sclerosis.

Therapeutic Inhibition of the Complement System in Diseases of the Central Nervous System

The complement system plays critical roles in development, homeostasis, and regeneration in the central nervous system (CNS) throughout life; however, complement dysregulation in the CNS can lead to damage and disease. Complement proteins, regulators, and receptors are widely expressed throughout the CNS and, in many cases, are upregulated in disease. Genetic and epidemiological studies, cerebrospinal fluid (CSF) and plasma biomarker measurements and pathological analysis of post-mortem tissues have all implicated complement in multiple CNS diseases including multiple sclerosis (MS), neuromyelitis optica (NMO), neurotrauma, stroke, amyotrophic lateral sclerosis (ALS), Alzheimer's disease (AD), Parkinson's disease (PD), and Huntington's disease (HD). Given this body of evidence implicating complement in diverse brain diseases, manipulating complement in the brain is an attractive prospect; however, the blood-brain barrier (BBB), critical to protect the brain from potentially harmful agents in the circulation, is also impermeable to current complement-targeting therapeutics, making drug design much more challenging. For example, antibody therapeutics administered systemically are essentially excluded from the brain. Recent protocols have utilized "Trojan horse" techniques to transport therapeutics across the BBB or used osmotic shock or ultrasound to temporarily disrupt the BBB. Most research to date exploring the impact of complement inhibition on CNS diseases has been in animal models, and some of these studies have generated convincing data; for example, in models of MS, NMO, and stroke. There have been a few recent clinical trials of available anti-complement drugs in CNS diseases associated with BBB impairment, for example the use of the anti-C5 monoclonal antibody (mAb) eculizumab in NMO, but for most CNS diseases there have been no human trials of anti-complement therapies. Here we will review the evidence implicating complement in diverse CNS disorders, from acute, such as traumatic brain or spine injury, to chronic, including demyelinating, neuroinflammatory, and neurodegenerative diseases. We will discuss the particular problems of drug access into the CNS and explore ways in which anti-complement therapies might be tailored for CNS disease.

Amyotrophic lateral sclerosis: The complement and inflammatory hypothesis

Amyotrophic lateral sclerosis (ALS) is a devastating, neurodegenerative motor neuron disease. The aetiology of ALS remains an enigma which hinders the design of an effective treatment to prevent, postpone, or reverse the pathophysiological changes occurring during the aggressive progression of this disease. During the last decade, basic research within the innate immune system, and in particular the complement system, has revealed new, important roles of the innate immune system during development, homeostasis, and ageing within as well as outside the central nervous system. Several lines of evidence indicate that aberrant activation of the complement system locally in the central nervous system as well as systemically may be involved in the pathophysiology of ALS. This exciting new knowledge could point towards the innate immune system as a potential target of medical intervention in ALS. Recently, the historic perception of ALS as a central neurodegenerative disease has been challenged due to the significant amount of evidence of a dying-back mechanism causing the selective destruction of the motor neurons, indicating that disease onset occurs outside the borders of the blood-brain-barrier. This review addresses the function of the innate immune system during ALS. We emphasize the role of the complement system and specifically suggest the involvement of ficolin-3 from the lectin pathway in the pathophysiology of ALS.

Let's make microglia great again in neurodegenerative disorders

All of the common neurodegenerative disorders-Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis and prion diseases-are characterized by accumulation of misfolded proteins that trigger activation of microglia; brain-resident mononuclear phagocytes. This chronic form of neuroinflammation is earmarked by increased release of myriad cytokines and chemokines in patient brains and biofluids. Microglial phagocytosis is compromised early in the disease process, obfuscating clearance of abnormal proteins. This review identifies immune pathologies shared by the major neurodegenerative disorders. The overarching concept is that aberrant innate immune pathways can be targeted for return to homeostasis in hopes of coaxing microglia into clearing neurotoxic misfolded proteins.

Versatility of the complement system in neuroinflammation, neurodegeneration and brain homeostasis

The immune response after brain injury is highly complex and involves both local and systemic events at the cellular and molecular level. It is associated to a dramatic over-activation of enzyme systems, the expression of proinflammatory genes and the activation/recruitment of immune cells. The complement system represents a powerful component of the innate immunity and is highly involved in the inflammatory response. Complement components are synthesized predominantly by the liver and circulate in the bloodstream primed for activation. Moreover, brain cells can produce complement proteins and receptors. After acute brain injury, the rapid and uncontrolled activation of the complement leads to massive release of inflammatory anaphylatoxins, recruitment of cells to the injury site, phagocytosis and induction of blood brain barrier (BBB) damage. Brain endothelial cells are particularly susceptible to complement-mediated effects, since they are exposed to both circulating and locally synthesized complement proteins. Conversely, during neurodegenerative disorders, complement factors play distinct roles depending on the stage and degree of neuropathology. In addition to the deleterious role of the complement, increasing evidence suggest that it may also play a role in normal nervous system development (wiring the brain) and adulthood (either maintaining brain homeostasis or supporting regeneration after brain injury). This article represents a compendium of the current knowledge on the complement role in the brain, prompting a novel view that complement activation can result in either protective or detrimental effects in brain conditions that depend exquisitely on the nature, the timing and the degree of the stimuli that induce its activation. A deeper understanding of the acute, subacute and chronic consequences of complement activation is needed and may lead to new therapeutic strategies, including the ability of targeting selective step in the complement cascade.

Proteome analysis of body fluids for amyotrophic lateral sclerosis biomarker discovery

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder of motor neurons leading to death of the patients, mostly within 2-5 years after disease onset. The pathomechanism of motor neuron degeneration is only partially understood and therapeutic strategies based on mechanistic insights are largely ineffective. The discovery of reliable biomarkers of disease diagnosis and progression is the sine qua non of both the revelation of insights into the ALS pathomechanism and the assessment of treatment efficacies. Proteomic approaches are an important pillar in ALS biomarker discovery. Cerebrospinal fluid is the most promising body fluid for differential proteome analyses, followed by blood (serum, plasma), and even urine and saliva. The present study provides an overview about reported peptide/protein biomarker candidates that showed significantly altered levels in certain body fluids of ALS patients. These findings have to be discussed according to proposed pathomechanisms to identify modifiers of disease progression and to pave the way for the development of potential therapeutic strategies. Furthermore, limitations and advantages of proteomic approaches for ALS biomarker discovery in different body fluids and reliable validation of biomarker candidates have been addressed.

Biomarkers for amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is the most common form of motor neuron disease. ALS is a fatal neurodegenerative disease and clinical diagnosis typically takes many months to complete. Early disease diagnosis through the use of biomarkers may aid in correct clinical management of patients and possibly delay time to ventilator and morbidity. This review explores the progress of biomarker discovery efforts for ALS and the many challenges that remain. Included are different technologies utilized in biomarker discovery efforts (proteomic, genomic and metabolomic) and putative biomarkers uncovered using these techniques. These studies have discovered genetic mutations leading to familial forms of ALS, and specific protein alterations that occur in biological fluids (cerebrospinal fluid and blood) and/or tissues of ALS subjects. More recent high-throughput technologies have revealed panels of proteomic or metabolic biomarkers that can discriminate between ALS and control groups. The identification of disease-specific biomarkers will provide opportunities to develop early diagnostic measures as well as surrogate markers to monitor disease progression and test drug efficacy in clinical trials.

C1q induction and global complement pathway activation do not contribute to ALS toxicity in mutant SOD1 mice

Accumulating evidence from mice expressing ALS-causing mutations in superoxide dismutase (SOD1) has implicated pathological immune responses in motor neuron degeneration. This includes microglial activation, lymphocyte infiltration, and the induction of C1q, the initiating component of the classic complement system that is the protein-based arm of the innate immune response, in motor neurons of multiple ALS mouse models expressing dismutase active or inactive SOD1 mutants. Robust induction early in disease course is now identified for multiple complement components (including C1q, C4, and C3) in spinal cords of SOD1 mutant-expressing mice, consistent with initial intraneuronal C1q induction, followed by global activation of the complement pathway. We now test if this activation is a mechanistic contributor to disease. Deletion of the C1q gene in mice expressing an ALS-causing mutant in SOD1 to eliminate C1q induction, and complement cascade activation that follows from it, is demonstrated to produce changes in microglial morphology accompanied by enhanced loss, not retention, of synaptic densities during disease. C1q-dependent synaptic loss is shown to be especially prominent for cholinergic C-bouton nerve terminal input onto motor neurons in affected C1q-deleted SOD1 mutant mice. Nevertheless, overall onset and progression of disease are unaffected in C1q- and C3-deleted ALS mice, thus establishing that C1q induction and classic or alternative complement pathway activation do not contribute significantly to SOD1 mutant-mediated ALS pathogenesis in mice.

Plasma and Cerebrospinal Fluid-Based Protein Biomarkers for Motor Neuron Disease

Motor neuron diseases (MNDs) and, in particular, amyotrophic lateral sclerosis (ALS), are a heterogeneous group of neurologic disorders characterized by the progressive loss of motor function. In ALS, a selective and relentless degeneration of both upper and lower motor neurons occurs, culminating in mortality typically within 5 years of symptom onset. However, survival rates vary among individual patients and can be from a few months to >10 years from diagnosis. Inadequacies in disease detection and treatment, along with a lack of diagnostic and prognostic tools, have prompted many to turn to proteomics-based biomarker discovery efforts. Proteomics refers to the study of the proteins expressed by a genome at a particular time, and the proteome can respond to and reflect the status of an organism, including health and disease states. Although an emerging field, proteomic applications promise to uncover biomarkers critical for differentiating patients with ALS and other MNDs from healthy individuals and from patients affected by other diseases. Ideally, these studies will also provide mechanistic information to facilitate identification of new drug targets for subsequent therapeutic development. In addition to proper experimental design, standard operating procedures for sample acquisition, preprocessing, and storage must be developed. Biological samples typically analyzed in proteomic studies of neurologic diseases include both plasma and cerebrospinal fluid (CSF). Recent studies have identified individual proteins and/or protein panels from blood plasma and CSF that represent putative biomarkers for ALS, although many of these proteins are not unique to this disease. Continued investigations are required to validate these initial findings and to further pursue the role of these proteins as diagnostic biomarkers or surrogate markers of disease progression. Protein biomarkers specific to ALS will additionally function to evaluate drug efficacy in clinical trials and to identify novel targets for drug design. It is hoped that proteomic technologies will soon integrate the basic biology of ALS with mechanistic disease information to achieve success in the clinical setting.

Biomarkers in frontotemporal lobar degenerations--progress and challenges

Neuronal and glial changes associated with tau, TAR DNA binding protein of ∼43 kDa (TDP-43), and fused in sarcoma (FUS) together constitute the pathologic spectrum of frontotemporal lobar degeneration (FTLD). Most patients with FTLD present with prominent behavior or language changes, sometimes accompanied by extrapyramidal symptoms or motor neuron disease. Identification of FTLD patients with mutations in genes for tau, TDP-43, and FUS lends strong support for their pathogenic roles in FTLD, and elucidation of their dysfunction will pave the way for development of substrate specific therapy. However, there remains no reliable biomarker for early detection of FTLD or prediction of underlying FTLD pathologic change. Clinical syndromes usually reflects the earliest affected brain regions where atrophy can be visualized on structural MRI, but neither clinical nor structural imaging-based biomarkers has been accurately correlated with underlying pathology on the individual patient level. Biochemical markers in the cerebrospinal fluid (CSF) have also been investigated in FTLD and related disorders, including amyotrophic lateral sclerosis (ALS) and progressive supranuclear palsy (PSP). However, their accuracy and pathologic significance need to be confirmed in future multi-center studies. Here we review the progress made in FTLD biomarkers, including clinical phenotype/feature characterization, neuropsychological analysis, CSF and plasma analytes, and patterns of brain atrophy and network dysfunction detectable on brain imaging. Given the pathologic overlap of FTLD with ALS and PSP, collaboration with specialists in those fields will be essential in the translation of promising FTLD biomarkers into clinical practice.

Innate immunity in the nervous system

The complement (C) system plays a central role in innate immunity and bridges innate and adaptive immune responses. A fine balance of C activation and regulation mediates the elimination of invading pathogens and the protection of the host from excessive C deposition on healthy tissues. If this delicate balance is disrupted, the C system may cause injury and contribute to the pathogenesis of various diseases, including neurodegenerative disorders and neuropathies. Here we review evidence indicating that C factors and regulators are locally synthesized in the nervous system and we discuss the evidence supporting the protective or detrimental role of C activation in health, injury, and disease of the nerve.

Neuroprotection in stroke by complement inhibition and immunoglobulin therapy

Activation of the complement system occurs in a variety of neuroinflammatory diseases and neurodegenerative processes of the CNS. Studies in the last decade have demonstrated that essentially all of the activation components and receptors of the complement system are produced by astrocytes, microglia, and neurons. There is also rapidly growing evidence to indicate an active role of the complement system in cerebral ischemic injury. In addition to direct cell damage, regional cerebral ischemia and reperfusion (I/R) induces an inflammatory response involving complement activation and generation of active fragments, such as C3a and C5a anaphylatoxins, C3b, C4b, and iC3b. The use of specific inhibitors to block complement activation or their mediators such as C5a, can reduce local tissue injury after I/R. Consistent with therapeutic approaches that have been successful in models of autoimmune disorders, many of the same complement inhibition strategies are proving effective in animal models of cerebral I/R injury. One new form of therapy, which is less specific in its targeting of complement than monodrug administration, is the use of immunoglobulins. Intravenous immunoglobulin (IVIG) has the potential to inhibit multiple components of inflammation, including complement fragments, pro-inflammatory cytokine production and leukocyte cell adhesion. Thus, IVIG may directly protect neurons, reduce activation of intrinsic inflammatory cells (microglia) and inhibit transendothelial infiltration of leukocytes into the brain parenchyma following an ischemic stroke. The striking neuroprotective actions of IVIG in animal models of ischemic stroke suggest a potential therapeutic potential that merits consideration for clinical trials in stroke patients.

The complement factor C5a contributes to pathology in a rat model of amyotrophic lateral sclerosis

Complement activation products are elevated in the cerebrospinal fluid and spinal cord of patients with amyotrophic lateral sclerosis (ALS). In this study, we demonstrate complement system involvement in a rodent model of ALS (human SOD1(G93A) transgenic rats). With end-stage disease, SOD1(G93A) rats displayed marked deposition of C3/C3b, and a significant up-regulation of the C5aR in the lumbar spinal cord. This was associated with increased numbers of C5aR-positive astrocytes. However, expression of C5L2, the alternative receptor for C5a, was highest on motor neurons early in the disease process. To determine the contribution of C5a to the pathology displayed by this model of ALS, rats were administered an orally active, selective C5aR antagonist (PMX205; 1 mg/kg/day, oral). Animals treated with PMX205 displayed a significant extension of survival time and a reduction in end-stage motor scores, as compared with vehicle-treated rats. PMX205-treated animals also displayed reduced levels of astroglial proliferation in the lumbar spinal cord. This study provides the first demonstration of an involvement of C5a in an ALS model and suggests that inhibitors of complement activation could be beneficial in the treatment of this neurodegenerative disease.

Shifting the balance: cell-based therapeutics as modifiers of the amyotrophic lateral sclerosis–specific neuronal microenvironment

✓ Recent advances in the laboratory have improved the current understanding of neurobiological mechanisms underlying the initiating events and pathological progression observed in amyotrophic lateral sclerosis (ALS). Whereas initial studies have revealed the late-stage intracellular cascades contributing to neuronal dysfunction and cell death, more recently collected data have begun to elucidate the presence and importance of a “non–cell autonomous” component indicating that affected glial cell subtypes may serve distinct and required roles. Pharmacological interventions for ALS have largely been disappointing likely in part because they have failed to address either the proximate events contributing to neuronal dysfunction and death or the deleterious contributions of non-neuronal cells within the local microenvironment. Alternatively, cell-based therapeutics offer the potential of a multifaceted approach oriented toward the dual ends of protecting remaining viable neurons and attempting to restore neuronal function lost as a manifestation of disease progression. The authors review the evolving knowledge of disease initiation and progression, with specific emphasis on the role of affected glia as crucial contributors to the observed ALS phenotype. This basis is used to underscore the potential roles of cell-based therapeutics as modifiers of the ALS-specific microenvironment.

Early complement activation increases in the brain in some aged normal subjects

Complement activation is increased in Alzheimer's disease (AD) and may contribute to the development and progression of this disorder. To compare early complement activation between normal and AD brain specimens, C4d and iC3b concentrations were measured in hippocampus, entorhinal cortex, temporal cortex, parietal cortex, and cerebellum from aged normal and AD subjects n=10-14 for both), and in hippocampus and entorhinal cortex from younger normal subjects (n=5-6). C4d and iC3b levels increased 2.3- to 4.6-fold in AD versus aged normal specimens (all P <0.05), with lowest concentrations of these activation proteins generally in cerebellum. No significant differences were present between aged and younger normal C4d and iC3b levels in hippocampus or entorhinal cortex. However, the concentrations of these proteins were markedly increased in several aged normal specimens. Normal subject age was moderately associated with both C4d (r=0.49) and iC3b (r=0.53) concentrations in the hippocampus. Increased brain complement activation in some elderly individuals may promote the subsequent development of AD.

Inflammatory processes in amyotrophic lateral sclerosis

Neuroinflammation is a characteristic of pathologically affected tissue in several neurodegenerative disorders. These changes can be observed in the brainstem and spinal cord of amyotrophic lateral sclerosis (ALS) cases and in mouse models of the disease. They include an accumulation of large numbers of activated microglia and astrocytes, as well as small numbers of T cells, mostly adhering to postcapillary venules. Accompanying biochemical alterations include the appearance of numerous molecules characteristic of free-radical attack, the occurrence of proteins associated with activation of the complement cascade, and a sharp upregulation of the enzyme cyclooxygenase 2 (COX-2). Anti-inflammatory agents may have a role to play in treating ALS. COX-2 is a particularly attractive target because of its marked increase in ALS spinal cord.

Cerebrospinal fluid filtration in amyotrophic lateral sclerosis

By means of a randomized, controlled and open study the authors wanted to find out if cerebrospinal (CSF)-filtration was of substantial benefit to patients with sporadic amyotrophic lateral sclerosis (SALS). Five SALS patients, aged 51-75 years, being treated with riluzole underwent CSF-filtration daily over five days (group A). Five other SALS patients, aged 52-70 years, were treated only with riluzole (group B). Although all five patients in the first group reported a subjective benefit following CSF- filtration, the Norris score, the Frenchay score, the vital capacity, the ulnar nerve F-wave persistence and the peak-ratio of the brachial biceps and anterior tibial muscles did not change significantly after five days of therapy, either in group A or in group B. In conclusion, filtration of 200-250 ml CSF daily, over five days, does not seem to have a substantial therapeutic effect in patients with SALS.

Cerebrospinal fluid complement activation in neurological diseases

Laser nephelometry (LN) is a rapid and very sensitive method for simultaneous determination of albumin, immunoglobulins, C3c and C4 in diluted serum and paired cerebrospinal fluid (CSF) samples. It is very useful in routine analyses. Determination of C3c and C4 covers classical as well as alternative pathways of complement activation. In CSF, they are mostly derived from and related to serum values. Under physiological conditions, the addition of intrathecal C4 synthesis is likely. The incidence of complement activation within CSF is also influenced by the method of choice (native molecules, activation products and complexes, inhibitors) and the mode of interpretation of results according to the functional state of the blood-brain barrier (BBB). Calculation of indexes and the modified Reiber's graph method are valid means of detection of complement activation within CSF. Complement activation within CSF was confirmed in 36% (111/302) of neurological patients examined; in 55% (48/87) of patients with inflammatory and demyelinating diseases, in 40% (37/94) of patients with CNS infections and complications, in 33% (4/12) of patients with motor neuron diseases, in 27% (11/40) of patients with spinal cord compression and sequelae, in 25% (8/32) of patients with neoplastic disease, and in 17% (6/37) of patients with cerebrovascular accidents.

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.