The role of complement in myasthenia gravis: serological evidence of complement consumption in vivo

BACKGROUND: Antibodies to the acetylcholine receptor (AChR) titin and the ryanodine receptor (RyR) occur in myasthenia gravis (MG). These antibodies are capable of complement activation in vitro. The involvement of the complement system should cause consumption of complement components such as C3 and C4 in vivo. MATERIALS AND METHODS: Complement components C3 and C4 were assayed in sera from 78 AChR antibody-positive MG patients and 52 healthy controls. Forty-eight of the patient sera contained titin antibodies as well, and 20 were also RyR antibody-positive. RESULTS: MG patients with AChR antibody concentrations above the median (11.2 nmol/l) had significantly lower mean C3 and C4 concentrations in serum compared to those with AChR antibody concentrations below the median. Titin antibody-positive MG patients, titin antibody-negative early-onset MG patients, titin antibody-negative late-onset MG patients, and controls had similar C3 and C4 concentrations. Nor did mean C3 and C4 concentrations differ in MG patients with RyR antibodies. Patients with severe MG (grades 4 and 5) had similar C3 and similar C4 levels compared to those with mild MG (grades 1 and 2). CONCLUSION: An increased in vivo complement consumption was detected in MG patients with high AChR antibody concentrations, unrelated to MG severity and non-AChR muscle antibodies.     

Role of complement and potential of complement inhibitors in myasthenia gravis and neuromyelitis optica spectrum disorders: a brief review

Journal of Neurology - The complement system is a powerful member of the innate immune system. It is highly adept at protecting against pathogens, but exists in a delicate balance between its...     

Amyloid myopathy presenting with rhabdomyolysis: evidence of complement activation

At age of 57 years, a man experienced an episode of rhabdomyolysis. On that occasion muscle biopsy was not performed, however monoclonal gammopathy of undetermined significance (MGUS) was diagnosed. Further he developed a moderate proximal muscle weakness with CK level persistently elevated (1000-1200U/l). When he came to our observation, at age 67, a muscle biopsy revealed an amyloid myopathy and multiple myeloma was at the same time disclosed. Terminal complement complex C5b9 (membrane attack complex) deposits were found in the vessel walls and muscle fibers surface depicted by amyloid. Our case suggests to keep in mind the possibility that amyloid myopathy may begin as an isolate episode of rhabdomyolysis. The detection of complement complex C5b9 suggests that complement cascade is implicated in the muscular damage of amyloid myopathy.     

Innate and adaptive immunity in amyotrophic lateral sclerosis: evidence of complement activation

Increasing evidence suggests a role for the immune system in amyotrophic lateral sclerosis (ALS). To determine the extent of the immune activation in ALS we analyzed the expression and cellular distribution of components of innate and adaptive immunity in spinal cord (SC) and motor cortex (MCx) from patients with rapid and slow sporadic ALS and controls. High levels of mRNA and protein of classical complement pathway, C1q and C4, as well as the downstream complement components C3 and C5b-9 were found in all ALS samples. Furthermore, we found higher numbers of activated microglia, reactive astrocytes, dendritic cells (DCs) and CD8(+) T-cells in ALS than in control tissue. Rapid ALS cases had more dendritic cells than slow ALS cases, whereas slow ALS cases had more activated microglia than rapid cases. Our findings demonstrate a persistent and prominent activation of both innate and adaptive immunity in ALS. We propose a complement-driven immune response which may contribute to the progression of the inflammation and ultimately lead to even more motor neuron injury.     

Plasma exchange in myasthenia gravis: changes in serum complement and immunoglobulins

Serum concentrations of C4, IgG, IgA, and IgM were followed in 8 selected patients with myasthenia gravis (MG) during a 5-day course of plasma exchange (PE), using donor plasma as a replacement solution. C3 activation products (C3b, iC3b and C3c) and the terminal SC5b-9 complement complex were measured in 4 of the patients. All patients improved during the treatment, including 2 patients without detectable antibodies to AChR in serum. The main findings of the study were marked complement activation and an approximately 50% fall in the serum concentrations of IgM and C4 during PE, independent of the concentrations in the donor plasma. The concentrations of IgG and IgA did not change significantly. The fall in C4 during PE is presumably caused by C4 consumption. We postulate that the fall in IgM is an effect of a complement-induced vasodilatation and that PE-induced complement consumption may influence the effect of PE in patients with MG.     

Antisulfatide polyneuropathy: antibody-mediated complement attack on peripheral myelin

Increased titers of circulating antisulfatide antibodies are consistently associated with a variety of chronic axonal and demyelinating polyneuropathy syndromes. Previous studies have shown that the pattern of antisulfatide binding to neural tissues correlates with the type of neuropathy. This suggests a possible role for antisulfatide antibodies in inducing peripheral nerve dysfunction, although their exact contribution to the pathogenesis of neuropathy is still unknown. We examined sural nerve biopsy specimens from two patients with sensorimotor and small fiber sensory neuropathy associated with high titers of IgM monoclonal antibodies to sulfatide. Electrophysiological and pathological findings were consistent with predominant demyelination in the patient with sensorimotor involvement, whereas evidence of demyelination was obtained only by teased fiber examination in the other patient. The ultrastructural study disclosed in both cases the presence of myelinated fibers with widely spaced myelin, due to a separation of leaflets of the intraperiod lines. Immunocytochemistry, performed on frozen sections, demonstrated the presence of IgM and complement product C3d bound to myelin sheaths of almost all fibers. Few fibers were immunoreactive for complement components C1q and C5. In addition, the terminal complement complex neoantigen C5b-C9, not associated with S protein, was detected on some myelinated fibers. The results suggest that, at the least in some forms of demyelinating neuropathy associated with antisulfatide antibodies, pathological changes are complement mediated. Our data further confirm previous clinical and experimental observations that complement activation initiates separation of myelin intraperiod lines. Received: 26 January 1998 / Revised, accepted: 25 May 1998     

Thermal response to zymosan: the differential role of complement

OBJECTIVES: This study was designed to determine whether the complement (C) system may be involved in the febrile response to zymosan (Zym), a glycan derived from yeast cell walls. METHODS: Cobra venom factor (CVF) at 100 U/animal or its vehicle, pyrogen-free saline (PFS), was injected intravenously (i.v.) into guinea pigs to deplete serum C. Eighteen hours later, a low or high dose of Zym or its vehicle, PFS, was administered i.v. or intraperitoneally (i.p.) to these animals. The core temperature (T(c)) was measured continuously by thermocouples. Serum C levels were determined by sheep erythrocyte hemolytic assay. RESULTS: Zym at 1 mg/kg caused a 1 degrees C T(c) rise that was not significantly affected by CVF pretreatment. However, CVF-induced hypocomplementation converted the T(c) fall ( approximately 1.2 degrees C) produced by 100 mg/kg of Zym i.p. into a 1 degrees C T(c) rise. Similarly, CVF pretreatment did not affect the T(c) rise caused by 0.5 mg/kg of Zym i.v., but converted the T(c) fall induced by 25 mg/kg i.v. into a 1 degrees C T(c) rise. A separate experiment showed that 25, but not 0.5 mg/kg of Zym i.v., decreased serum C by 34% in 15 min; C did not recover over the next 6 h. A second i.v. injection of 25 mg Zym/kg 210 min later, when the T(c) had recovered but the serum C had not, yielded a smaller and briefer T(c) fall. CONCLUSION: These results suggest that Zym is inherently pyrogenic, but this effect is manifested only when the dose of zymosan is too small to activate C or when C has been reduced by prior activation.     

Immunohistology of temporal arteritis: phenotyping of infiltrating cells and deposits of complement components

Summary Deposition of complement factors, immunoglobulins and infiltrating cells was evaluated by immunohistochemical staining in 30 temporal artery biopsy specimens from patients suffering from temporal arteritis and/or polymyalgia rheumatica and in controls. In the temporal arteritis group infiltrating cells, classic complement, alternative complement and lytic complex activation were detected. In specimens from patients suffering from only polymyalgia rheumatica there was unexpected evidence of classic complement and lytic complex activation. We conclude that immuno-histochemistry provides support for the concept of temporal arteritis and polymyalgia being based on the same pathological process.     

Two new cases of XYY chromosome complement: and a review of the literature

Two cases with XYY chromosome complement are presented and compared with 153 cases described in the literature. Some patients with abnormalities of personality development and manifest psychopathology may have sex chromosome abnormalities and should be studied further for the interaction of genetic and environmental factors in personality development. In particular, tall, schizoid impulsive men with a history of criminality, arson or sexual offences should be screened for this particular genetic configuration. Because of the biased manner by which most of the cases are found, it is not yet known whether an XYY genotype results in a characteristic phenotype. What is needed is a genetic study of a normal population and a prospective study of newborns with various genotypes which would, unfortunately, create complex research and ethical problems.     

Effect of tranexamic acid, t-AMCHA, and its cis-isomer on the complement system in vitro and in vivo: possible relationship between coagulation and complement systems.

In vivo and in vitro effects of tranexamic acid, t-AMCHA, on the complement system were studied. Trans-AMCHA scarcely inhibited CH50 and Cl$\text{s}$ up to 30 mM in vitro. Inhibitions of AP50 and C(1,4,2)H50 were about 20 % and 40 % at 30 mM, respectively. No inhibition of CH50 was shown at the concentration of less than 5 mM of t-AMCHA in vitro. When 1 gr. of t-AMCHA was injected intravenously, and blood was drawn at intervals, CH50 was suppressed to 92 % of normal level at 10 min, then returned to normal at 120 min. The concentration of t-AMCHA in serum at 10 min was about 0.6 mM. Since CH50 was measured by diluting serum 150 to 300 times, the concentration of t-AMCHA in the assay system was at the order of μM. Direct effects of t-AMCHA on complement components, therefore, are improbable at such low concentrations.Blood clotted in the presence of 1 to 5 mM of t-AMCHA, and serum was obtained. CH50 of such sera was suppressed. When blood clotted, ATEe hydrolyzing enzyme, possibly Cl$\text{s}$, was activated. Both t- and cis-AMCHA increased the activation at the concentration of up to 5 mM. Although coagulation processes enhanced the activation of plasminogen by streptokinase (SK), plasmin did not have much influence on the activation of ATEe hydrolyzing enzyme at low concentration, but at the high concentration plasmin seemed to destroy this enzyme. Differences in the effects of t-AMCHA on the complement in vivo and in vitro may be due to the consumption of the complement system during coagulation processes, and t-AMCHA facilitated the consumption. Since both trans- and cis-forms of AMCHA were effective, the enhancement of the consumption in the presence of AMCHA was not due to inhibition of plasmin.     

Intrathecal complement activation in neurological diseases evaluated by analysis of the terminal complement complex

The terminal complement complex (TCC) was determined in plasma and cerebrospinal fluid (CSF) from 208 neurological patients. Elevated CSF TCC levels were observed in higher frequencies in patients with infectious diseases (80%), radiculoneuritis (62%), multiple sclerosis (30%), and miscellaneous autoimmune diseases (27%) than in patients with miscellaneous non-inflammatory diseases (2-13%). The plasma level of TCC was significantly increased only in the infectious group. No positive correlation was observed between the plasma and the CSF TCC concentration in the whole patient population nor in subgroups divided according to blood-brain barrier function. Furthermore, the CSF TCC concentration did not correlate with the serum/CSF albumin ratio or with CSF total protein concentration when this was below 1.0 g/l. It is concluded that an elevated TCC concentration in CSF reflects intrathecal complement activation and that quantification of TCC in CSF may be a valuable supplement in the examination of neurological diseases.     

Immunoglobulins and complement factors in senile plaques

Summary Immunoperoxidase techniques were used to obtain information about the possible presence of serum factors in senile plaques. We found only in plaques consisting of an amyloid core surrounded by a corona of degenerating neurites small amounts of IgG and light chains (kappa and labda). These immunoglobulins were principally localized in the corona and not in the central amyloid core. further it was found that all plaques contain the complement factors C₁q, C₃b, C₃c, C₃d and C₄. Senile plaques lacked C₅, C₃ pro-activator and properdin. The possible significance of these findings in the gensis of the senile plaques and amyloid formation is discussed.     

精神分裂症患者血清免疫球蛋白及补体含量分析

目的探讨体液免疫异常在精神分裂症发病过程中的作用。方法利用速率散射比浊法测定25例首发精神分裂症患者、30例经抗精神病药物治疗患者血清中IgG、IgA、IgM及补体C3、C4含量,并与正常人作对照分析。结果未治疗组血清中IgG、IgA含量显著高于正常人及治疗组(P<0.01),而IgM则无显著性差异(P>0.05),治疗组及未治疗组血清C3含量显著低于正常对照组(P<0.01)。结论精神分裂症患者存在一定程度的体液免疫异常,对其发病可能有一定影响。     

Reaction of complement factors and proteasomes in experimental encephalitis

Herpes simplex virus type 1 (HSV-1) encephalitis causes a deleterious inflammation and elevated intracranial pressure. As a step towards examining the origin of the inflammation, we here report the response of circulating proteasomes and complement factors in blood and cerebrospinal fluid (CSF) in rats infected with HSV-1. Infection was via the nasal route, with 1.1 × 10⁴ plaque-forming units of HSV-1 strain 2762 given in one or both nostrils. A sandwich enzyme-linked immunosorbent assay was used to study the level of 26S proteasomes and their complex formation with complement factors 3 and 4. HSV-1 infection in the rat causes a complex formation between complement factors and proteasomes, which we designate compleasomes. In the first experiment, with HSV-1 given in both nostrils, compleasomes containing complement factors 3 and 4 increased significantly in both blood plasma and CSF. The concentration of proteasomes in plasma was similar in controls and infected rats (320 ± 163 vs. 333 ± 125 ng/ml). In the second experiment, with HSV-1 given in one nostril, CSF levels were 1 ± 1 ng/ml in controls and 56 ± 22 ng/ml in the HSV-1 group, whereas the total protein concentration in CSF remained the same in the two groups. The compleasome response was limited to CSF, with a highly significant difference between infected rats and controls (n = 11, p < 0.001). It was possible to mimic the reaction between proteasomes and complements 3 and 4 in vitro in the presence of ATP.     

Association of factor H of the alternative pathway of complement with agrin and complement receptor 3 in the Alzheimer's disease brain

Factor H, a regulatory protein of the alternative pathway of complement (APC), is present in amyloid-beta (Abeta) plaques in Alzheimer's disease (AD). Abeta plaques also contain significant amounts of heparan sulfate proteoglycans (HSPGs), such as agrin, as well as numerous activated microglia expressing increased levels complement receptor 3 (CR3). Here, we show the colocalization of each of these molecules in the AD brain and the functional capacity for these molecules to bind to one another in vitro. We propose that CR3 receptors expressed by microglia are used for ligand binding to factor H bound to HSPGs and Abeta in plaques in the AD brain.     

Serum complement composition of myasthenia gravis

Serum complements of C1q C1, C4, BF, C1-INH and C5 were measured by single immunodiffusion in 54 patients with myasthenia gravis (MG), 46 normal control (NC) and 42 cases of other neurological disorders. It was found that C1-INH, C5 levels in MG were significantly higher than that in other groups (P less than 0.01). The serum levels of C1-INH, C5 were not related to the clinical type and the stage of the illness. These data suggest that endplate receptors might be disrupted through complement mediated immunoreaction.     

The complement and immunoglobulin levels in NMO patients

Since the discovery of aquaporin-4 (AQP4) antibody a decade ago, neuromyelitis optica (NMO) has been distinguished from multiple sclerosis (MS). MS mainly features T lymphocyte-oriented autoimmune responses while NMO is more precisely influenced by humoral immunity, among which the complement activation has always been reckoned as an important mechanism. The AQP4 antibody, namely NMO-IgG, adds to new evidence of how complement affects the severity of NMO. We compared the levels of complement (C3, C4, CH50) and immunoglobulins (IgG, IgM, IgA) between NMO patients and controls. Groups with AQP4 antibody positive and negative NMO patients were also compared with controls, respectively, aiming to elaborate on the relationship between complement activation and immunoglobulins. We also compared these indexes together with expanded disability status scale (EDSS) between two different groups in NMO patients and endeavored to figure out their correlations with each other. Complement and immunoglobulins were compared between NMO patients in acute phase and non-acute phase of the disease to find out the level fluctuation of CH50 and other indexes during different stages of NMO. We analyzed NMO patients (n = 88) and controls (n = 44) for IgG, IgM, IgA, other indexes like CH50, C3, C4 have also been explored between the two groups. Furthermore, we investigated whether these antibodies could mediate complement-dependent cytotoxicity. Thus, the NMO patients were split into two groups with or without AQP4 antibody to find out the status of NMO-IgG in the development and severity of the disease. EDSS was used as criteria for the evaluating the seriousness of NMO. Comparison between NMO patients in acute stage and non-acute stage of the disease was also made for a better understanding of the disease. Compared with controls, NMO patients had much higher IgG (13.984 ± 5.981 mg/ml, 11.430 ± 3.254 mg/ml, P < 0.01) but lower CH50 (respectively, 43.55 ± 12.172 U/L, 50.66 ± 12.523 U/L, P < 0.01). While IgG increased in Anti-AQP4 antibody-positive NMO patients, CH50 dropped in this group when compared with AQP4-negative patients. When compared with controls, both of the NMO groups had enhanced IgG and decreased CH50 though only AQP4-positive NMO patients showed significance (IgG 15.004 ± 6.613 mg/ml, 11.430 ± 3.254 mg/ml, P < 0.01) (CH50, respectively, 41.12 ± 12.581U/L, 50.66 ± 12.523 U/L, P < 0.01). C4 was also decreased though without evident significance (0.215 ± 0.118 mg/ml, 0.260 ± 0.133 mg/ml, P = 0.069). Those NMO patients in acute phase (with the course of newly attack of less than 1 month) had increased immunoglobulin (IgG 14.991 ± 6.639 mg/ml, 12.460 ± 4.490 mg/ml) but decreased complement (CH50 42.755 ± 12.403 U/L, 44.743 ± 11.890 U/L) than those who passed the acute phase. There was correlation between IgG and CH50 (R = ?0.402, P < 0.01) in NMO patients. Relationship was also found between IgG and EDSS (R = 0.609, P < 0.001), CH50 and EDSS (R = ?0.333, P < 0.01). These results indicate that NMO patients had enhanced immunoglobulin in acute phase but decreased complement. The complement was correlated with immunoglobulin. Among the two NMO groups, the complement system was only activated in NMO-IgG positive patients, which might indicate a potential different pathogenetic mechanism in NMO-IgG negative patients. Also, patients’ disability of the former group was more serious than their counterparts. Those patients in acute phase obviously had increased immunoglobulin but decreased complement. Thus, we have come to the conclusion that in AQP4-positive NMO patients, immunoglobulin activates complement system, which influences the functions of NMO patients.     

Immunoglobulins and the complement system in Horton's headache

In 39 patients with Horton's headache (bgh) and 70 controls the total complement level and the levels of its C3 and C4 fractions, as well as IgG, IgA and IgM levels were determined. It was found that in bgh patients the mean level of the C3 fraction was significantly below that in the control group, while the C4 level was still within normal range. The levels of immunoglobulins were not statistically significantly different in these groups with the exception of IgA which was significantly lower in bgh cases. The author thinks that low C3 fraction level may be a part of the clinical pattern of bgh and is due to activation of the complement system on the alternative pathway. On the other hand, bgh attacks could not be qualified into any known type of allergic reaction.