The role of the complement system in arthritis and stroke

Complement is part of the innate immune system and functions primarily as a first line of defense against invading microorganisms. It is a complex cascade, which can be activated via three pathways: the classical, alternative and mannan-binding lectin pathway. To study the role of the complement system in disease pathogenesis, we have generated mice deficient in C3, which is the central protein in all three pathways, and mice deficient in factor B, which is critical for the activation of the alternative pathway. Using these complement deficient mice, we have found that complement activation by both the classical and the alternative pathways plays a critical role in two models of rheumatoid arthritis, namely collagen-induced arthritis and arthritis induced by arthritogenic monoclonal antibodies. Our findings indicate that antibody binding to collagen triggers the activation of the classical pathway, which is then amplified by the alternative pathway.When subjected to permanent focal brain ischemia by middle cerebral artery occlusion, the infarction volume in the C3 deficient mice was significantly larger than that in control mice. These results, together with the finding of reduced number of presumed neural progenitor cells in the penumbra and infarction area of C3 deficient mice, implicate the complement system as a positive regulator of neurogenesis in brain ischemia. Thus, besides its well-established role in host defense against pathogens, the complement system may have additional roles in disease pathogenesis: its activation appears to augment tissue damage in autoantibody-associated diseases such as arthritis, but may contribute to tissue repair after cerebral ischemia.Designing drugs targeting complement activation may be a rational therapeutic strategy. However, great care will have to be executed in defining and reaching the proper balance between the two contradictory effects of the complement system

Neuromyelitis optica spectrum disorder with increased aquaporin-4 microparticles prior to autoantibodies in cerebrospinal fluid: a case report

Abstract Background Neuromyelitis optica spectrum disorders are severe autoimmune inflammatory diseases of the central nervous system associated with the presence of immunoglobulin G antibodies against the water channel protein aquaporin-4. During exacerbation, specific aquaporin-4 immunoglobulin G may be produced intrathecally. We measured extracellular aquaporin-4 microparticles in the cerebrospinal fluid of a patient who later developed the typical symptoms and signs of a neuromyelitis optica spectrum disorder. Case presentation A 17-year-old South American girl developed acute severe motor and vocal tics and difficulties in walking, peripheral numbness, muscle pain, and bilateral headache. At age 22, she had a multitude of motor and psychiatric symptoms. Over the years, she fulfilled the diagnostic criteria for anorexia nervosa, depression, sleep disorder, obsessive-compulsive disorder, generalized anxiety disorder, panic disorder, agoraphobia, social anxiety disorder, development coordination disorder, attention-deficit/hyperactivity disorder, hypomania, pediatric autoimmune neuropsychiatric disorders associated with streptococcal infections, conversion disorder, psychosis, and schizotypal personality syndrome. At age 24, she was found to have elevated titers of aquaporin-4 antibodies in serum, suggestive of probable neuromyelitis optica. She subsequently developed visual impairment, and swollen optic nerves were verified by magnetic resonance imaging. She was thus treated with a chimeric monoclonal antibody targeted against the pan-B-cell marker CD20 (rituximab), and almost all symptoms, including the psychiatric symptoms, rapidly decreased. We found a significant increase of extracellular microparticles of aquaporin-4 in cerebrospinal fluid sampled from our patient when she was 22 years old, 2 years before the full clinical development of neuromyelitis optica. Conclusions Microparticles of aquaporin-4 represent subcellular arrangements that may influence the pathogenesis of neuromyelitis optica spectrum disorders and may serve as biomarkers for the underlying cellular disturbances. The increase of aquaporin-4 microparticles in cerebrospinal fluid may be used for early diagnostic purposes; for prevention; and for evaluation of effective treatment, long-term follow-up studies, and elucidating the pathophysiology in neuromyelitis optica spectrum disorders. Further studies of aquaporin-4 microparticles in cerebrospinal fluid of patients with neuromyelitis optica and similar neuropsychiatric disorders are thus called for

The Temporal Retinal Nerve Fiber Layer Thickness Is the Most Important Optical Coherence Tomography Estimate in Multiple Sclerosis

BackgroundReduced peripapillary retinal nerve fiber layer (pRNFL) and combined ganglion cell and inner plexiform layer (GCIP) thicknesses as measured by optical coherence tomography (OCT) have been observed in multiple sclerosis (MS) patients. The purpose was to determine the most associative OCT measure to level of cognitive and physical disability in MS.MethodsData were collected from 546 MS patients and 175 healthy controls (HCs). We compared the average pRNFL, temporal pRNFL (T-pRNFL), overall inner ganglion cell/inner plexiform layer (GCIP), and the overall ganglion cell complex (GCC) including macular RNFL and GCIP thicknesses measurements in differentiating MS subtypes from HCs. The association between OCT measures, Expanded Disability Status Scale (EDSS), and Symbol Digit Modalities Test (SDMT) were assessed using generalized estimating equations models.ResultsBoth peripapillary and macular OCT measurements could differentiate all MS subtypes from HCs. The SDMT score was significantly associated with reduced thickness of all OCT measures, mostly in average pRNFL (0.14 µm, P = 0.001) and T-pRNFL (0.17 µm, P < 0.001). The EDSS score was significantly associated with reduced inner retinal layer thickness. The largest reduction was seen in T-pRNFL (−1.52 μm, P < 0.001) and inner GCC (−1.78 μm, P < 0.001).ConclusionThe T-pRNFL is highly sensitive and associated with level of both cognitive and physical disability

Efficacy and Safety of Rituximab for New-Onset Generalized Myasthenia Gravis The RINOMAX Randomized Clinical Trial

IMPORTANCE Rituximab is a third-line option for refractory generalized myasthenia gravis (MG) based on empirical evidence, but its effect in new-onset disease is unknown. OBJECTIVE To investigate the efficacy and safety of rituximab compared with placebo as an add-on to standard of care for MG. DESIGN, SETTING, AND PARTICIPANTS This randomized, double-blind, placebo-controlled study took place throughout 48 weeks at 7 regional clinics in Sweden. Key inclusion criteria were age older than 18 years, onset of generalized symptoms within 12 months or less, and a Quantitative Myasthenia Gravis (QMG) score of 6 or more. Patients were screened from October 20, 2016, to March 2, 2020. Key exclusion criteria included pure ocular MG, suspected thymoma, previous thymectomy, and prior noncorticosteroid immunosuppressants or high doses of corticosteroids. INTERVENTIONS Participants were randomized 1:1 without stratification to a single intravenous infusion of 500 mg of rituximab or matching placebo. MAIN OUTCOMES AND MEASURES Minimal disease manifestations at 16 weeks defined as a QMG score of 4 or less with prednisolone, 10 mg or less daily, and no rescue treatment. RESULTS Of 87 potentially eligible patients, 25 were randomized to rituximab (mean [SD] age, 67.4 [13.4] years; 7 [28%] female) and 22 to placebo (mean [SD] age, 58 [18.6] years; 7 [32%] female). Compared with placebo, a greater proportion with rituximab met the primary end point; 71% (17 of 24) in the rituximab group vs 29% (6 of 21) in the placebo group (Fisher exact test P = .007; probability ratio, 2.48 [95% CI, 1.20-5.11]). Secondary end points, comparing changes in Myasthenia Gravis Activities of Daily Living and Myasthenia Gravis Quality of Life at 16 weeks with QMG at 24 weeks did not differ between groups with censoring for rescue treatment (per-protocol analysis) but were in favor of active treatment when rescue treatment was taken into account by worst rank imputation (post hoc analysis). Rescue treatments were also more frequent in the placebo arm (rituximab: 1 [4%]; placebo, 8 [36%]). One patient in the placebo arm had a myocardial infarction with cardiac arrest and 1 patient in the active arm experienced a fatal cardiac event. CONCLUSIONS AND RELEVANCE A single dose of 500 mg of rituximab was associated with greater probability of minimal MG manifestations and reduced need of rescue medications compared with placebo. Further studies are needed to address long-term benefit-risk balance with this treatment.Funding Agencies|Swedish Medical Research Council [2015-00887, 2020-02700]</p

Complement: a novel factor in basal and ischemia-induced neurogenesis

Through its involvement in inflammation, opsonization, and cytolysis, the complement protects against infectious agents. Although most of the complement proteins are synthesized in the central nervous system (CNS), the role of the complement system in the normal or ischemic CNS remains unclear. Here we demonstrate for the first time that neural progenitor cells and immature neurons express receptors for complement fragments C3a and C5a (C3a receptor (C3aR) and C5a receptor). Mice that are deficient in complement factor C3 (C3(−/−)) lack C3a and are unable to generate C5a through proteolytic cleavage of C5 by C5-convertase. Intriguingly, basal neurogenesis is decreased both in C3(−/−) mice and in mice lacking C3aR or mice treated with a C3aR antagonist. The C3(−/−) mice had impaired ischemia-induced neurogenesis both in the subventricular zone, the main source of neural progenitor cells in adult brain, and in the ischemic region, despite normal proliferative response and larger infarct volumes. Thus, in the adult mammalian CNS, complement activation products promote both basal and ischemia-induced neurogenesis