Systemic delivery of human GlyR IgG antibody induces GlyR internalization into motor neurons of brainstem and spinal cord with motor dysfunction in mice

Aims

Progressive encephalomyelitis with rigidity and myoclonus (PERM) is a life‐threatening condition often associated with highly raised serum antibodies to glycine receptors (GlyRs); these bind to the surface of large neurons and interneurons in rodent brain and spinal cord sections and, in vitro, inhibit function and reduce surface expression of the GlyRs. The effects in vivo have not been reported.

Methods

Purified plasma IgG from a GlyR antibody‐positive patient with PERM, and a healthy control (HC), was injected daily into the peritoneal cavity of mice for 12 days; lipopolysaccharide (LPS) to open the blood–brain barrier, was injected on days 3 and 8. Based on preliminary data, behavioural tests were only performed 48 h post‐LPS on days 5–7 and 10–12.

Results

The GlyR IgG injected mice showed impaired ability on the rotarod from days 5 to 10 but this normalized by day 12. There were no other behavioural differences but, at termination (d13), the GlyR IgG‐injected mice had IgG deposits on the neurons that express GlyRs in the brainstem and spinal cord. The IgG was not only on the surface but also inside these large GlyR expressing neurons, which continued to express surface GlyR.

Conclusions

Despite the partial clinical phenotype, not uncommon in passive transfer studies, the results suggest that the antibodies had accessed the GlyRs in relevant brain regions, led to antibody‐mediated internalization and increased GlyR synthesis, compatible with the temporary loss of function.

CSF findings in patients with voltage gated potassium channel antibody associated limbic encephalitis

Recently, a new subtype of limbic encephalitis (LE) has been described, serologically characterized by the presence of antibodies against voltage gated potassium channels (VGKC, to be called VGKC-LE). Only little is known about CSF findings in this new disorder. Here we report the results of 29 lumbar punctures in 17 patients with VGKC-LE. Slight pleocytosis, mainly consisting of lymphocytes and monocytes, and elevated total protein concentrations were present in 41 and 47%, respectively. Intrathecal immunoglobulin (Ig) synthesis as defined by the presence of CSF-specific oligoclonal IgG bands, an increased IgG index, or an elevated IgG, IgA, or IgM ratio, was not detected in any of the patients, but dysfunction of the blood-CSF barrier was found in 35%. CSF findings were normal in 23%.

CONCLUSIONS

Unlike paraneoplastic LE, VGKC-LE is not frequently associated with intrathecal Ig production or markedly elevated white cell counts. Thus, normal CSF findings do not preclude the disease. VGKC-Ab should, therefore, be determined whenever LE is clinically suspected, irrespective of the presence or absence of inflammatory CSF changes.

Hypothermia in VGKC antibody-associated limbic encephalitis

Voltage-gated potassium channel antibody (VGKC-Ab)-associated limbic encephalitis (LE) is a recently described syndrome that broadens the spectrum of immunotherapy-responsive central nervous system disorders. Limbic encephalitis is typically characterised by a sub-acute onset of disorientation, amnesia and seizures, but the clinical spectrum is not yet fully defined and the syndrome could be under-diagnosed. We here describe the clinical profile of four patients with VGKC-Ab-associated LE who had intermittent, episodic hypothermia. One of the patients also described a prodrome of severe neuropathic pain preceding the development of limbic symptoms. Both of these novel symptoms responded well to immunosuppressive therapy, with concurrent amelioration of amnesia/seizures.

Absence of antibodies to glutamate receptor type 3 (GluR3) in Rasmussen encephalitis

OBJECTIVE

To determine the prevalence of serum antibodies to the ionotropic glutamate receptor 3 (GluR3) in patients with Rasmussen encephalitis (RE), a severe epileptic disorder, and to compare with serum from control subjects and patients with intractable epilepsy (IE).

METHODS

The authors looked for serum immunoglobulin (Ig) G antibodies to GluR3 in 30 patients with RE, including two patients who had plasma exchange and 12 who had been treated with IV Igs with varying results, and 49 patients with IE and 23 healthy individuals, using ELISA with GluR3B peptide, Western blot analysis of recombinant full-length GluR3, immunoprecipitation of [35S]- and [125I]-labeled GluR3 extracellular domains, immunohistochemistry on rat brain sections, and electrophysiology of GluR3 expressed in Xenopus oocytes.

RESULTS

Low levels of antibodies to the GluR3B peptide were detected using ELISA in only 4 of the 79 patients with epilepsy (2 with RE and 2 with IE); binding to GluR3B in other sera was shown to be nonspecific. One other patient with IE had antibodies to recombinant GluR3 on Western blot analysis. However, none of the sera tested precipitated either the [35S]- or the [125I]-labeled GluR3 domains; none bound to rat brain sections in a manner similar to rabbit antibodies to GluR3; and none of the nine sera tested affected the electrophysiologic function of GluR3.

CONCLUSIONS

GluR3 antibodies were only infrequently found in Rasmussen encephalitis or intractable epilepsy.

Evidence of underdiagnosis of myasthenia gravis in older people

BACKGROUND

Myasthenia gravis is a potentially serious but treatable muscle disease caused by autoantibodies directed at the acetylcholine receptor (AChR) on the postsynaptic membrane of the neuromuscular junction. There is anecdotal evidence that the diagnosis is sometimes missed in older patients.

OBJECTIVE

To examine the incidence and age distribution of positive AChR antibodies in samples referred to diagnostic laboratories in the UK, and the prevalence of positive AChR antibodies in samples from a cohort of older individuals.

METHODS

Positive AChR antibody tests were identified from all UK centres registered for the assay with the European quality assurance scheme (EQAS) during 1997-99, and the age and sex specific incidence was calculated, based on the UK population. The prevalence of AChR antibodies in sera from a sample of 2000 individuals aged > or =60 years was determined.

RESULTS

3183 individuals had positive AChR antibody tests on routine screening during the years 1997 to 1999 in the UK, giving an annual incidence of 1.8/100 000. In both sexes, the age specific incidence rose steeply between the ages of 45 and 74, reaching 9.9/100 000 in men, and then fell, with a sharp decline above the age of 80. In the prevalence study, whereas only one serum from individuals aged 60-74 years was positive for AChR antibodies (0.12%), sera from eight individuals aged > or =75 years were positive (0.7%). Only one had a previous clinical diagnosis of myasthenia gravis but four others had histories of stroke or transient ischaemic attacks.

CONCLUSIONS

The sharp fall in the incidence of clinically recognised myasthenia gravis in people over 80 years of age in our national AChR antibody incidence study, and the high prevalence of previously unrecognised positive AChR antibodies in those > or =75 years old, suggest that myasthenia gravis may be substantially underdiagnosed in older people.

A role for autoantibodies in some cases of acquired non-paraneoplastic gut dysmotility

BACKGROUND

Antibody-mediated autoimmunity underlies a diverse range of disorders, particularly in the nervous system where domains of ion channels and receptors are potential targets. The aetiology of many adult-onset conditions of severe gut dysmotility is not known. We looked for antibodies to neuronal antigens in patients with severe (slow-transit-type) constipation (STC).

METHODS

Eleven sera from adult-onset STC patients and 18 from childhood onset cases were tested by routine immunoprecipitation assays for antibodies against neuronal antigens including voltage-gated potassium channels (VGKCs), calcium channels (VGCCs), both muscle and neuronal acetylcholine receptor and glutamic acid decarboxylase (GAD). Results were compared with positive and negative control populations.

RESULTS

Two of the 11 sera from patients with adult-onset STC showed highly positive anti-VGKC antibodies. Both had onset of symptoms de novo in adulthood without evidence of autoimmune, neoplastic or neurological disease. One of these patients, and one other, had anti-GAD antibodies. None of the childhood-onset STC had evidence of anti-neuronal antibodies.

CONCLUSIONS

Anti-neuronal antibodies are found in some patients with a condition of severe acquired gut dysmotility of previously unknown aetiology. Future studies may demonstrate an autoimmune role for such antibodies.

Morvan's syndrome: peripheral and central nervous system and cardiac involvement with antibodies to voltage-gated potassium channels

Morvan's 'fibrillary chorea' or Morvan's syndrome is characterized by neuromyotonia (NMT), pain, hyperhydrosis, weight loss, severe insomnia and hallucinations. We describe a man aged 76 years with NMT, dysautonomia, cardiac arrhythmia, lack of slow-wave sleep and abnormal rapid eye movement sleep. He had raised serum antibodies to voltage-gated K(+) channels (VGKC), oligoclonal bands in his CSF, markedly increased serum norepinephrine, increased serum cortisol and reduced levels and absent circadian rhythms of prolactin and melatonin. The neurohormonal findings and many of the clinical features were very similar to those in fatal familial insomnia, a hereditary prion disease that is associated with thalamic degenerative changes. Strikingly, however, all symptoms in our MFC patient improved with plasma exchange. The patient died unexpectedly 11 months later. At autopsy, there was a pulmonary adenocarcinoma, but brain pathology showed only a microinfarct in the hippocampus and no thalamic changes. The NMT and some of the autonomic features are likely to be directly related to the VGKC antibodies acting in the periphery. The central symptoms might also be due to the direct effects of VGKC antibodies, or perhaps of other autoantibodies still to be defined, on the limbic system with secondary effects on neurohormone levels. Alternatively, changes in secretion of neurohormones in the periphery might contribute to the central disturbance. The relationship between VGKC antibodies, neurohormonal levels, autonomic, limbic and sleep disorders requires further study.

Potassium channel antibodies in two patients with reversible limbic encephalitis

Limbic encephalitis (LE) is often associated with lung, thymic, or testicular tumours and antibodies to Hu, CV2, or Ma2 (Ta) antigens. In these cases, it generally has a poor prognosis. Here we describe two patients with symptoms of LE, negative for typical paraneoplastic antibodies, in whom antibodies to voltage-gated potassium channels (VGKC) were detected retrospectively in serial serum samples. Patient 1 had a thymoma recurrence, but in patient 2 no tumour has been detected in the years following presentation. Plasma exchange was effective in reducing VGKC antibody levels, with substantial improvement in mental symptoms in patient 1. In patient 2, the VGKC antibodies fell spontaneously over two years, with almost complete recovery of mental function. Although neither patient had obvious neuromyotonia at presentation, both showed excessive secretions. We suggest that patients with limbic symptoms and excessive secretions should be tested for VGKC antibodies, and, if they are present, prompt and effective immunosuppressive treatment should be considered.

Localization of tumour necrosis factor production in cells at the materno/fetal interface in human pregnancy

Biologically active tumour necrosis factor (TNF) was detected in medium conditioned by incubation with explants of human pregnancy decidua or fetal chorionic villous tissue, taken in the first trimester and at term. Addition of endotoxin increased TNF release in most cases. ELISA assays gave similar results for TNF-alpha and also demonstrated low levels of TNF-beta. Using cell populations purified by flow cytometry, secretion of biologically active TNF was shown to be localized to the macrophages. Cytotrophoblast purified from term amniochorion produced no TNF. Both decidual and chorionic villous tissue at term contained mRNA for TNF-alpha and TNF-beta. TNF-alpha mRNA was confined to decidual macrophages in first trimester tissue, and was not present in chorionic cytotrophoblast. TNF-beta mRNA, in contrast, was detected in both macrophage and non-macrophage populations in term decidua.

Prostaglandins in the umbilical and uterine circulations during late pregnancy in the ewe

Prostaglandins (PG) E and F, and 13,14-dihydro-15-keto-prostaglandin F (PGFM) were measured in plasma collected from the umbilical artery and vein, the maternal carotid artery, and the utero-ovarian vein of pregnant sheep between 116 and 139 days of gestation. PGE levels were greater than PGF levels in the umbilical artery and vein and the maternal carotid artery, but not in the utero-ovarian vein. PGFM exceeded PGF in samples from all vessels. There was a significant vein-to-artery concentration difference for PGF and PGFM, but not for PGE, in the umbilical circulation. Utero-ovarian concentrations of all 3 PGs generally exceeded their concentrations in the maternal caroitd artery.

Concentrations of 6-oxo-prostaglandin F 1 alpha in the maternal and foetal plasma of sheep during spontaneous and induced parturition

The concentrations of 6-oxo-prostaglandin F 1 alpha (6-oxo-PGF 1 alpha) have been determined in maternal and foetal plasma from nine chronically catheterized sheep during late pregnancy and parturition. Labour occurred either spontaneously (three sheep) or was induced by continous intrafoetal infusion of Synacthen (ACTH 1-24; 0.24 mg/24 h; three sheep) or dexamethasone (1 mg/24 h; three sheep). During spontaneous and Synacthen-induced parturition, concentrations of 6-oxo-PGF 1 alpha in maternal and foetal plasma remained at basal levels until 24 h before delivery. At varying times during the 24 h before delivery, levels of 6-oxo-PGF 1 alpha in maternal and foetal plasma were generally increased. When parturition was induced with dexamethasone, however, no increase was observed in the foetal plasma although the concentration of 6-oxo-PGF 1 alpha in maternal plasma was raised close to delivery.

The concentrations of the prostaglandins E and F, 13 14-dihydro-15-oxo-prostaglandin F and thromboxane B2. In tissues obtained from women with and without pre-eclampsia

The concentrations of prostaglandins E (PGE) and F (PGF), 13, 14-dihydro-15-oxo-prostaglandin F (PGFM) and thromboxane B2 (TXB2) were measured by specific radioimmunoassays in tissues obtained from women with and without pre-eclampsia. The concentrations of PGE in the amnion, chorion, decidua and placenta obtained from subjects with pre-eclampsia were significantly lower than those from subjects without pre-eclampsia. The concentration of PGE in these tissues increased significantly with gestational age and correlated with urinary oestrogen excretion. PGF concentrations were lower in the amnion and placenta of the pre-eclamptics compared to those without pre-eclampsia. The concentrations of PGFM in the amnion, decidua, and myometrium were lower in the pre-eclamptics. No significant difference in the TXB2 concentrations between the two groups of subjects were found. It is suggested that the altered tissue concentrations of prostaglandins in pre-eclamptics are due to the effects of gestational age and oestrogens and may or may not be involved in the pathogenesis of pre-eclampsia.

Prostaglandin E, thromboxane B2 and 6-oxo-prostaglandin F1 alpha in amniotic fluid and maternal plasma of rhesus monkeys (Macaca mulatta) during the latter third of gestation

The concentrations of prostaglandin E (PGE), thromboxane B2 (TXB2) and 6-oxo-prostaglandin F1 alpha (6-oxo-PGF1 alpha) were measured by radioimmunoassay in serial samples of amniotic fluid and maternal peripheral plasma in the latter third of pregnancy in rhesus monkeys (Macaca mulatta). The samples were collected under ketamine-induced anaesthesia. The concentration of PGE was undetectable in amniotic fluid until a few days before delivery when a large increase was observed in three of the five animals. There were small increases of TXB2 and 6-oxo-PGF1 alpha in amniotic fluid before delivery. In maternal plasma the concentrations of PGE, TXB2 and 6-oxo-PGF1 alpha were generally higher and more variable than in amniotic fluid and did not increase with advancing gestation. It is suggested that increased production of primary prostaglandins occurs before, and is involved in, the onset of parturition in the rhesus monkey.

Specific change in the direction of prostaglandin synthesis by intra-uterine tissues of the rhesus monkey (Macaca mulatta) during late pregnancy

The rates of production of prostaglandin E (PGE), prostaglandin F (PGF) and 13, 14-dihydro-15-oxo-prostaglandin F (PGFM) by intra-uterine tissues from pregnant monkeys in vitro have been determined using a method of tissue superfusion. The amnion, chorion, placenta, decidua basalis, decidua parietalis and myometrium were obtained at Caesarean section during late pregnancy. Production of PGE by all tissues was significantly lower at term than during late pregnancy, whereas production of PGF by the amnion, chorion, decidua parietalis and myometrium was significantly greater. All tissues produced significantly more PGE than PGF and also, excepting the decidua basalis and decidua parietalis, more PGFM than PGF. Close to parturition the amnion was quantitatively (per unit weight) the major source of prostaglandins. It is suggested that a specific change in the direction of prostaglandin synthesis by intra-uterine tissues occurs near parturition in the rhesus monkey.