IgLON5-IgG: Innocent Bystander or Perpetrator?

Anti-IgLON5 (IgLON5-IgG)-associated disease is a newly defined clinical entity. This literature review aims to evaluate its pathogenesis, which remains a pivotal question. Features that favour a primary neurodegenerative mechanism include the non-inflammatory tauopathy neuropathological signature and overrepresentation of microtubule-associated protein tau (MAPT) H1/H1 genotype as seen in other sporadic tauopathies. In contrast, the cell-surface localisation of IgLON5, capability of anti-IgLON5 antibodies to exert direct in vitro pathogenicity and disrupt IgLON5 interactions with its binding partners, human leukocyte antigen (HLA)-DRB1*10:01 and HLA-DQB1*05:01 allele preponderance with high affinity binding of IgLON5 peptides, and responsiveness to immunotherapy favour a primary autoimmune process. The presentation and course of anti-IgLON5-associated disease is heterogenous; hence, we hypothesise that a multitude of immune mechanisms are likely simultaneously operational in this disease cohort.

HLA dependency and possible clinical relevance of intrathecally synthesized anti-IgLON5 IgG4 in anti-IgLON5 disease.

Background: Anti-IgLON5 disease is a rare chronic autoimmune disorder characterized by IgLON5 autoantibodies predominantly of the IgG4 subclass. Distinct pathogenic effects were described for anti-IgLON5 IgG1 and IgG4, however, with uncertain clinical relevance. Methods: IgLON5-specific IgG1-4 levels were measured in 46 sera and 20 cerebrospinal fluid (CSF) samples from 13 HLA-subtyped anti-IgLON5 disease patients (six females, seven males) using flow cytometry. Intervals between two consecutive serum or CSF samplings (31 and 10 intervals, respectively) were categorized with regard to the immunomodulatory treatment active at the end of the interval, changes of anti-IgLON5 IgG1 and IgG4 levels, and disease severity. Intrathecal anti-IgLON5 IgG4 synthesis (IS) was assessed using a quantitative method. Results: The median age at onset was 66 years (range: 54-75), disease duration 10 years (range: 15-156 months), and follow-up 25 months (range: 0-83). IgLON5-specific IgG4 predominance was observed in 38 of 46 (83%) serum and 11 of 20 (55%) CSF samples. Anti-IgLON5 IgG4 levels prior clinical improvement in CSF but not serum were significantly lower than in those prior stable/progressive disease. Compared to IgLON5 IgG4 levels in serum, CSF levels in HLA-DRB1*10:01 carriers were significantly higher than in non-carriers. Indeed, IgLON5-specific IgG4 IS was demonstrated not only in four of five HLA-DRB1*10:01 carriers but also in one non-carrier. Immunotherapy was associated with decreased anti-IgGLON5 IgG serum levels. In CSF, lower anti-IgLON5 IgG was associated with immunosuppressive treatments used in combination, that is, corticosteroids and/or azathioprine plus intravenous immunoglobulins or rituximab. Conclusion: Our findings might indicate that CSF IgLON5-specific IgG4 is frequently produced intrathecally, especially in HLA-DRB1*10:01 carriers. Intrathecally produced IgG4 may be clinically relevant. While many immunotherapies reduce serum IgLON5 IgG levels, more intense immunotherapies induce clinical improvement and may be able to target intrathecally produced anti-IgLON5 IgG. Further studies need to confirm whether anti-IgLON5 IgG4 IS is a suitable prognostic and predictive biomarker in anti-IgLON5 disease.

Anti-IgLON5 disease as a differential diagnosis of multiple system atrophy.

INTRODUCTION: Anti-immunoglobulin-like cell adhesion molecule 5 (IgLON5) disease is a rare autoimmune encephalitis that can mimic progressive supranuclear palsy or corticobasal syndrome. Moreover, anti-IgLON5 disease can present with symptoms characteristic of multiple system atrophy (MSA), such as cerebellar ataxia and autonomic dysfunction. However, the clinical features of anti-IgLON5 disease resembling MSA have not been well established. METHODS: We enrolled 35 patients with suspected MSA for whom anti-IgLON5 antibody tests were requested. We evaluated immunoglobulin G (IgG) against IgLON5 using cell-based assays. We also summarized the clinical characteristics of patients who were positive for anti-IgLON5 antibodies. RESULTS: We identified serum and cerebrospinal fluid anti-IgLON5 antibodies in three patients. These patients had many clinical features characteristic of MSA, including parkinsonism, cerebellar ataxia, severe orthostatic hypotension, acute respiratory failure, sleep parasomnia, vocal cord paralysis, and pyramidal tract signs. Clinical features atypical for MSA were myorhythmia, horizontal eye movement restriction, fasciculations, and painful muscle cramps. CONCLUSION: Anti-IgLON5 disease may be an important differential diagnosis of MSA. A comprehensive physical examination, including assessments of eye movement, lower motor neuron signs, and atypical involuntary movements, is important to avoid misdiagnosis.

New knowledge on anti-IgLON5 disease.

PURPOSE OF REVIEW: Anti-IgLON5 disease is characterized by a distinctive sleep disorder, associated with a heterogeneous spectrum of neurological symptoms. Initial autopsies showed a novel neuronal tauopathy predominantly located in the tegmentum of the brainstem. Recently, new diagnostic red flags, biomarkers predictors of response to immunotherapy, and novel insights into the autoimmune pathogenesis of the disease have been reported. RECENT FINDINGS: Patients with diagnosis of neurodegenerative dementia, progressive supranuclear palsy (PSP) or with motor-neuron disease (MND)-like syndrome have been reported to have IgLON5 antibodies, which are the hallmark of anti-IgLON5 disease. Second, low levels of neurofilament light chain in serum and cerebrospinal fluid of patients at disease onset could be a predictor of immunotherapy response. Recent neuropathological studies indicate that the neuronal tau deposits occur late in the course of the disease. Moreover, IgLON5 antibodies induce cytoskeletal changes in cultured hippocampal neurons suggesting that the tauopathy could be secondary of the IgLON5 antibody effects. SUMMARY: Anti-IgLON5 disease can mimic and should be considered in atypical presentations of MND, neurodegenerative dementia and PSP. Neurofilament light chain levels seem promising biomarker for disease prognosis. Finally, the neuropathological and in vitro experimental studies strengthen the autoimmune hypothesis of the disease.

HLA-DQB1*05 subtypes and not DRB1*10:01 mediates risk in anti-IgLON5 disease.

Anti-IgLON5 disease is a rare and likely underdiagnosed subtype of autoimmune encephalitis. The disease displays a heterogeneous phenotype that includes sleep, movement and bulbar-associated dysfunction. The presence of IgLON5-antibodies in CSF/serum, together with a strong association with HLA-DRB1*10:01∼DQB1*05:01, supports an autoimmune basis. In this study, a multicentric human leukocyte antigen (HLA) study of 87 anti-IgLON5 patients revealed a stronger association with HLA-DQ than HLA-DR. Specifically, we identified a predisposing rank-wise association with HLA-DQA1*01:05∼DQB1*05:01, HLA-DQA1*01:01∼DQB1*05:01 and HLA-DQA1*01:04∼DQB1*05:03 in 85% of patients. HLA sequences and binding cores for these three DQ heterodimers were similar, unlike those of linked DRB1 alleles, supporting a causal link to HLA-DQ. This association was further reflected in an increasingly later age of onset across each genotype group, with a delay of up to 11 years, while HLA-DQ-dosage dependent effects were also suggested by reduced risk in the presence of non-predisposing DQ1 alleles. The functional relevance of the observed HLA-DQ molecules was studied with competition binding assays. These proof-of-concept experiments revealed preferential binding of IgLON5 in a post-translationally modified, but not native, state to all three risk-associated HLA-DQ receptors. Further, a deamidated peptide from the Ig2-domain of IgLON5 activated T cells in two patients, compared with one control carrying HLA-DQA1*01:05∼DQB1*05:01. Taken together, these data support a HLA-DQ-mediated T-cell response to IgLON5 as a potentially key step in the initiation of autoimmunity in this disease.

Inhibiting membrane rupture with NINJ1 antibodies limits tissue injury.

Plasma membrane rupture (PMR) in dying cells undergoing pyroptosis or apoptosis requires the cell-surface protein NINJ11. PMR releases pro-inflammatory cytoplasmic molecules, collectively called damage-associated molecular patterns (DAMPs), that activate immune cells. Therefore, inhibiting NINJ1 and PMR may limit the inflammation that is associated with excessive cell death. Here we describe an anti-NINJ1 monoclonal antibody that specifically targets mouse NINJ1 and blocks oligomerization of NINJ1, preventing PMR. Electron microscopy studies showed that this antibody prevents NINJ1 from forming oligomeric filaments. In mice, inhibition of NINJ1 or Ninj1 deficiency ameliorated hepatocellular PMR induced with TNF plus D-galactosamine, concanavalin A, Jo2 anti-Fas agonist antibody or ischaemia-reperfusion injury. Accordingly, serum levels of lactate dehydrogenase, the liver enzymes alanine aminotransaminase and aspartate aminotransferase, and the DAMPs interleukin 18 and HMGB1 were reduced. Moreover, in the liver ischaemia-reperfusion injury model, there was an attendant reduction in neutrophil infiltration. These data indicate that NINJ1 mediates PMR and inflammation in diseases driven by aberrant hepatocellular death.

Increased Intrathecal B and Plasma Cells in Patients With Anti-IgLON5 Disease: A Case Series.

BACKGROUND AND OBJECTIVES: Despite detection of autoantibodies, anti-IgLON5 disease was historically considered a tau-associated neurodegenerative disease, with limited treatment options and detrimental consequences for the patients. Observations in increasing case numbers hint toward underlying inflammatory mechanisms that, early detection provided, open a valuable window of opportunity for therapeutic intervention. We aimed to further substantiate this view by studying the CSF of patients with anti-IgLON5. METHODS: We identified 11 patients with anti-IgLON5 from our database and compared clinical, MRI, and CSF findings with a cohort of 20 patients with progressive supranuclear palsy (PSP) (as a noninflammatory tauopathy) and 22 patients with functional neurologic disorder. RESULTS: Patients with anti-IgLON5 show inflammatory changes in routine CSF analysis, an increase in B-lymphocyte frequency, and the presence of plasma cells in comparison to the PSP-control group and functional neurologic disease controls. Patients with intrathecal plasma cells showed a clinical response to rituximab. DISCUSSION: Our findings indicate the importance of inflammatory mechanisms, in particular in early and acute anti-IgLON5 cases, which may support the use of immune-suppressive treatments in these cases. The main limitation of the study is the small number of cases due to the rarity of the disease.

The CD6/ALCAM pathway promotes lupus nephritis via T cell-mediated responses.

T cells are central to the pathogenesis of lupus nephritis (LN), a common complication of systemic lupus erythematosus (SLE). CD6 and its ligand, activated leukocyte cell adhesion molecule (ALCAM), are involved in T cell activation and trafficking. Previously, we showed that soluble ALCAM is increased in urine (uALCAM) of patients with LN, suggesting that this pathway contributes to disease. To investigate, uALCAM was examined in 1038 patients with SLE and LN from 5 ethnically diverse cohorts; CD6 and ALCAM expression was assessed in LN kidney cells; and disease contribution was tested via antibody blockade of CD6 in murine models of SLE and acute glomerulonephritis. Extended cohort analysis offered resounding validation of uALCAM as a biomarker that distinguishes active renal involvement in SLE, irrespective of ethnicity. ALCAM was expressed by renal structural cells whereas CD6 expression was exclusive to T cells, with elevated numbers of CD6+ and ALCAM+ cells in patients with LN. CD6 blockade in models of spontaneous lupus and immune-complex glomerulonephritis revealed significant decreases in immune cells, inflammatory markers, and disease measures. Our data demonstrate the contribution of the CD6/ALCAM pathway to LN and SLE, supporting its use as a disease biomarker and therapeutic target.

Ocular Motor Abnormalities in Anti-IgLON5 Disease.

Objective: Anti-IgLON5 disease forms an interface between neuroinflammation and neurodegeneration and includes clinical phenotypes that are often similar to those of neurodegenerative diseases. An early diagnosis of patients with anti-IgLON5 disease and differentiation from neurodegenerative diseases is necessary and may have therapeutic implications. Methods: In our small sample size study we investigated oculomotor function as a differentiating factor between anti-IgLON5 disease and neurodegenerative disorders. We examined ocular motor and vestibular function in four patients suffering from anti-IgLON5 disease using video-oculography (VOG) and a computer-controlled rotational chair system (sampling rate 60 Hz) and compared the data with those from ten age-matched patients suffering from progressive supranuclear palsy (PSP) and healthy controls (CON). Results: Patients suffering from anti-IgLON5 disease differed from PSP most strikingly in terms of saccade velocity and accuracy, the presence of square wave jerks (SWJ) (anti-IgLON5 0/4 vs. PSP 9/10) and the clinical finding of supranuclear gaze palsy (anti-IgLON5 1/4). The presence of nystagmus, analysis of smooth pursuit eye movements, VOR and VOR suppression was reliable to differentiate between the two disease entities. Clear differences in all parameters, although not always significant, were found between all patients and CON. Discussion: We conclude that the use of VOG as a tool for clinical neurophysiological assessment can be helpful in differentiating between patients with PSP and patients with anti-IgLON5 disease. VOG could have particular value in patients with suspected PSP and lack of typical Parkinson's characteristics. future trials are indispensable to assess the potential of oculomotor function as a biomarker in anti-IgLON5 disease.

Prospective Isolation and Characterization of Chondroprogenitors from Human Chondrocytes Based on CD166/CD34/CD146 Surface Markers.

PURPOSE: Chondrocytes, isolated from articular cartilage, are routinely utilized in cell-based therapeutics for the treatment of cartilage pathologies. However, restoration of the biological tissue faces hindrance due to the formation of primarily fibrocartilaginous repair tissue. Chondroprogenitors have been reported to display superiority in terms of their chondrogenic potential and lesser proclivity for hypertrophy. In line with our recent results, comparing chondroprogenitors and chondrocytes, we undertook isolation of progenitors from the general pool of chondrocytes, based on surface marker expression, namely, CD166, CD34, and CD146, to eliminate off-target differentiation and generate cells of stronger chondrogenic potential. This study aimed to compare chondrocytes, chondroprogenitors, CD34-CD166+CD146+ sorted chondrocytes, and CD34-CD166+CD146- sorted chondrocytes. METHODS: Chondrocytes obtained from 3 human osteoarthritic knee joints were subjected to sorting, to isolate CD166+ and CD34- subsets, and then were further sorted to obtain CD146+ and CD146- cells. Chondrocytes and fibronectin adhesion-derived chondroprogenitors served as controls. Assessment parameters included reverse transcriptase polymerase chain reaction for markers of chondrogenesis and hypertrophy, trilineage differentiation, and total GAG/DNA content. RESULTS: Based on gene expression analysis, CD34-CD166+CD146+ sorted chondrocytes and chondroprogenitors displayed comparability and significantly higher chondrogenesis with a lower tendency for hypertrophy when compared to chondrocytes and CD34-CD166+CD146- sorted chondrocytes. The findings were also reiterated in multilineage potential differentiation with the 146+ subset and chondroprogenitors displaying lower calcification and chondroprogenitors displaying higher total GAG/DNA content compared to chondrocytes and 146- cells. CONCLUSION: This unique progenitor-like population based on CD34-CD166+CD146+ sorting from chondrocytes exhibits efficient potential for cartilage repair and merits further evaluation for its therapeutic application.

Leucine-Rich Glioma-Inactivated 1 versus Contactin-Associated Protein-like 2 Antibody Neuropathic Pain: Clinical and Biological Comparisons.

Pain is a under-recognized association of leucine-rich glioma-inactivated 1 (LGI1) and contactin-associated protein-like 2 (CASPR2) antibodies. Of 147 patients with these autoantibodies, pain was experienced by 17 of 33 (52%) with CASPR2- versus 20 of 108 (19%) with LGI1 antibodies (p = 0.0005), and identified as neuropathic in 89% versus 58% of these, respectively. Typically, in both cohorts, normal nerve conduction studies and reduced intraepidermal nerve fiber densities were observed in the sampled patient subsets. In LGI1 antibody patients, pain responded to immunotherapy (p = 0.008), often rapidly, with greater residual patient-rated impairment observed in CASPR2 antibody patients (p = 0.019). Serum CASPR2 antibodies, but not LGI1 antibodies, bound in vitro to unmyelinated human sensory neurons and rodent dorsal root ganglia, suggesting pathophysiological differences that may underlie our clinical observations. ANN NEUROL 2021;90:683-690.

Stabilin-1 plays a protective role against Listeria monocytogenes infection through the regulation of cytokine and chemokine production and immune cell recruitment.

Scavenger receptors are part of a complex surveillance system expressed by host cells to efficiently orchestrate innate immune response against bacterial infections. Stabilin-1 (STAB-1) is a scavenger receptor involved in cell trafficking, inflammation, and cancer; however, its role in infection remains to be elucidated. Listeria monocytogenes (Lm) is a major intracellular human food-borne pathogen causing severe infections in susceptible hosts. Using a mouse model of infection, we demonstrate here that STAB-1 controls Lm-induced cytokine and chemokine production and immune cell accumulation in Lm-infected organs. We show that STAB-1 also regulates the recruitment of myeloid cells in response to Lm infection and contributes to clear circulating bacteria. In addition, whereas STAB-1 appears to promote bacterial uptake by macrophages, infection by pathogenic Listeria induces the down regulation of STAB-1 expression and its delocalization from the host cell membrane.We propose STAB-1 as a new SR involved in the control of Lm infection through the regulation of host defense mechanisms, a process that would be targeted by bacterial virulence factors to promote infection.

Spinal Ninjurin2 contributes to the neuropathic pain via NF-κB-mediated neuroinflammation in the spared sciatic nerve injury rats.

OBJECT: Ninjurin2 (nerve injury induced protein 2, NINJ2) is a molecule which mediates cell-to-cell and cell-to-extracellular matrix interactions in the nervous system. Clinical study shows NINJ2 is associated with the development of postherpetic neuralgia. However, it is lack of direct evidence that NINJ2 participated in neuropathic pain. In this study, we aim to investigate the role of NINJ2 in the development of neuropathic pain in spared sciatic nerve injury rats and the underlying mechanism. METHOD: Spared sciatic nerve injury (SNI) models were established. The level of NINJ2 and p-p65 (a NF-κB family member) were measured in SNI rats by western blots and immunofluorescent staining. Lentivirus encoding small interfering RNA targeting NINJ2 (RNAi) was intrathecally injected into rats. Then the change of pain behavior of rats induced by NINJ2 RNAi was tested by Von-Frey hairs. The change of p-p65 in the spinal cord in rats after NINJ2 RNAi treatment was also measured by western blots. inhibitor of p-p65-induced change of TNF-α, IL-1ß, and IL-6 levels were measured by ELISA. RESULTS: NINJ2 and p-p65 were increased in the spinal cord of SNI rats on the 3, 7, 14th days after modeling. NINJ2 were mainly expressed in neurons, and co-located with p-p65 in the spinal dorsal horn. When down regulating the level of NINJ2 by RNAi, the development of pain in SNI rats was partially blocked. Phosphorylation of p65 was also inhibited by NINJ2 RNAi. Blocking the phosphorylation of NF-κB pathway could inhibit the increase of TNF-α, IL-1ß, and IL-6 in the spinal cord of SNI rats. CONCLUSION: NINJ2 protein was increased in the spinal cord of SNI rats. It participated in the development of nerve injury-induced neuropathic pain by activating neuroinflammation in the spinal cord via NF-κB pathway. This study provides a new target to investigate the mechanism of neuropathic pain.

Longitudinal CSF Findings in Autoimmune Encephalitis-A Monocentric Cohort Study.

Autoimmune encephalitis (AIE) poses a diagnostic challenge due to its heterogeneous clinical presentation, which overlaps with various neurological and psychiatric diseases. During the diagnostic work-up, cerebrospinal fluid (CSF) is routinely obtained, allowing for differential diagnostics as well as for the determination of antibody subclasses and specificities. In this monocentric cohort study, we describe initial and serial CSF findings of 33 patients diagnosed with antibody-associated AIE (LGI1 (n=8), NMDA (n=7), CASPR2 (n=3), IgLON5 (n=3), AMPAR (n=1), GAD65/67 (n=4), Yo (n=3), Ma-1/2 (n=2), CV2 (n=2)). Routine CSF parameters of 12.1% of AIE patients were in normal ranges, while 60.6% showed elevated protein levels and 45.4% had intrathecal oligoclonal bands (OCBs). Repeated CSF analyses showed a trend towards normalization of initial pathological CSF findings, while relapses were more likely to be associated with increased cell counts and total protein levels. OCB status conversion in anti-NMDARE patients coincided with clinical improvement. In summary, we show that in routine CSF analysis at diagnosis, a considerable number of patients with AIE did not exhibit alteration in the CSF and therefore, diagnosis may be delayed if antibody testing is not performed. Moreover, OCB status in anti-NMDAR AIE patients could represent a potential prognostic biomarker, however further studies are necessary to validate these exploratory findings.

Antibodies to the Caspr1/contactin-1 complex in chronic inflammatory demyelinating polyradiculoneuropathy.

Previous studies have described the clinical, serological and pathological features of patients with chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) and antibodies directed against the paranodal proteins neurofascin-155, contactin-1 (CNTN1), contactin-associated protein-1 (Caspr1), or nodal forms of neurofascin. Such antibodies are useful for diagnosis and potentially treatment selection. However, antibodies targeting Caspr1 only or the Caspr1/CNTN1 complex have been reported in few patients with CIDP. Moreover, it is unclear if these patients belong to the same pathophysiological subgroup. Using cell-based assays in routine clinical testing, we identified sera from patients with CIDP showing strong membrane reactivity when both CNTN1 and Caspr1 were co-transfected (but not when CNTN1 was transfected alone). Fifteen patients (10 male; aged between 40 and 75) with antibodies targeting Caspr1/CNTN1 co-transfected cells were enrolled for characterization. The prevalence of anti-Caspr1/CNTN1 antibodies was 1.9% (1/52) in the Sant Pau CIDP cohort, and 4.3% (1/23) in a German cohort of acute-onset CIDP. All patients fulfilled European Federation of Neurological Societies/Peripheral Nerve Society (EFNS/PNS) definite diagnostic criteria for CIDP. Seven (47%) were initially diagnosed with Guillain-Barré syndrome due to an acute-subacute onset. Six (40%) patients had cranial nerve involvement, eight (53%) reported neuropathic pain and 12 (80%) ataxia. Axonal involvement and acute denervation were frequent in electrophysiological studies. Complete response to intravenous immunoglobulin was not observed, while most (90%) responded well to rituximab. Enzyme-linked immunosorbent assay (ELISA) and teased nerve fibre immunohistochemistry confirmed reactivity against the paranodal Caspr1/CNTN1 complex. Weaker reactivity against Caspr1 transfected alone was also detected in 10/15 (67%). Sera from 13 of these patients were available for testing by ELISA. All 13 samples reacted against Caspr1 by ELISA and this reactivity was enhanced when CNTN1 was added to the Caspr1 ELISA. IgG subclasses were also investigated by ELISA. IgG4 was the predominant subclass in 10 patients, while IgG3 was predominant in other three patients. In conclusion, patients with antibodies to the Caspr1/CNTN1 complex display similar serological and clinical features and constitute a single subgroup within the CIDP syndrome. These antibodies likely target Caspr1 primarily and are detected with Caspr1-only ELISA, but reactivity is optimal when CNTN1 is added to Caspr1 in cell-based assays and ELISA.

Neurodegeneration Induced by Anti-IgLON5 Antibodies Studied in Induced Pluripotent Stem Cell-Derived Human Neurons.

Anti-IgLON5 disease is a progressive neurological disorder associated with autoantibodies against a neuronal cell adhesion molecule, IgLON5. In human postmortem brain tissue, the neurodegeneration and accumulation of hyperphosphorylated tau (p-tau) are found. Whether IgLON5 antibodies induce neurodegeneration or neurodegeneration provokes an immune response causing inflammation and antibody formation remains to be elucidated. We investigated the effects of anti-IgLON5 antibodies on human neurons. Human neural stem cells were differentiated for 14-48 days and exposed from Days 9 to 14 (short-term) or Days 13 to 48 (long-term) to either (i) IgG from a patient with confirmed anti-IgLON5 antibodies or (ii) IgG from healthy controls. The electrical activity of neurons was quantified using multielectrode array assays. Cultures were immunostained for ß-tubulin III and p-tau and counterstained with 4',6-Diamidine-2'-phenylindole dihydrochloride (DAPI). To study the impact on synapses, cultures were also immunostained for the synaptic proteins postsynaptic density protein 95 (PSD95) and synaptophysin. A lactate dehydrogenase release assay and nuclei morphology analysis were used to assess cell viability. Cultures exposed to anti-IgLON5 antibodies showed reduced neuronal spike rate and synaptic protein content, and the proportion of neurons with degenerative appearance including p-tau (T205)-positive neurons was higher when compared to cultures exposed to control IgG. In addition, cell death was increased in cultures exposed to anti-IgLON5 IgG for 21 days. In conclusion, pathological anti-IgLON5 antibodies induce neurodegenerative changes and cell death in human neurons. This supports the hypothesis that autoantibodies may induce the neurodegenerative changes found in patients with anti-IgLON5-mediated disease. Furthermore, this study highlights the potential use of stem cell-based in vitro models for investigations of antibody-mediated diseases. As anti-IgLON5 disease is heterogeneous, more studies with different IgLON5 antibody samples tested on human neurons are needed.

Lymphatic Endothelial Cell Activation and Dendritic Cell Transmigration Is Modified by Genetic Deletion of Clever-1.

Clever-1 also known as Stabilin-1 and FEEL-1 is a scavenger molecule expressed on a subpopulation of anti-inflammatory macrophages and lymphatic endothelial cells (LECs). However, its role in regulating dendritic cell (DC) trafficking and subsequent effects on immunity have remained unexplored. In this study, we demonstrate that DC trafficking from the skin into the draining lymph nodes is compromised in the absence of Clever-1. By adoptive transfer approaches we further show that the poor trafficking is due to the impaired entrance of DCs into afferent lymphatics. Despite this, injections of ovalbumin-loaded DCs into the footpads induced a stronger proliferative response of OT II T cells in the draining lymph nodes. This could be explained by the increased MHC II expression on DCs and a less tolerogenic phenotype of LECs in lymph nodes of Clever-1 knockout mice. Thus, although fewer DCs reach the nodes, they are more active in creating antigen-specific immune responses. This suggests that the DCs migrating to the draining lymph node within Clever-1 positive lymphatics experience immunosuppressive interactions with LECs. In conclusion, besides being a trafficking molecule on lymphatic vasculature Clever-1 is immunosuppressive towards migrating DCs and thus, regulates the magnitude of immune responses created by incoming DCs in the draining lymph nodes.