Paraneoplastic and Other Autoimmune Encephalitides: Antineuronal Antibodies, T Lymphocytes, and Questions of Pathogenesis

Autoimmune and paraneoplastic encephalitides represent an increasingly recognized cause of devastating human illness as well as an emerging area of neurological injury associated with immune checkpoint inhibitors. Two groups of antibodies have been detected in affected patients. Antibodies in the first group are directed against neuronal cell surface membrane proteins and are exemplified by antibodies directed against the N-methyl-D-aspartate receptor (anti-NMDAR), found in patients with autoimmune encephalitis, and antibodies directed against the leucine-rich glioma-inactivated 1 protein (anti-LGI1), associated with faciobrachial dystonic seizures and limbic encephalitis. Antibodies in this group produce non-lethal neuronal dysfunction, and their associated conditions often respond to treatment. Antibodies in the second group, as exemplified by anti-Yo antibody, found in patients with rapidly progressive cerebellar syndrome, and anti-Hu antibody, associated with encephalomyelitis, react with intracellular neuronal antigens. These antibodies are characteristically found in patients with underlying malignancy, and neurological impairment is the result of neuronal death. Within the last few years, major advances have been made in understanding the pathogenesis of neurological disorders associated with antibodies against neuronal cell surface antigens. In contrast, the events that lead to neuronal death in conditions associated with antibodies directed against intracellular antigens, such as anti-Yo and anti-Hu, remain poorly understood, and the respective roles of antibodies and T lymphocytes in causing neuronal injury have not been defined in an animal model. In this review, we discuss current knowledge of these two groups of antibodies in terms of their discovery, how they arise, the interaction of both types of antibodies with their molecular targets, and the attempts that have been made to reproduce human neuronal injury in tissue culture models and experimental animals. We then discuss the emerging area of autoimmune neuronal injury associated with immune checkpoint inhibitors and the implications of current research for the treatment of affected patients.publishedVersio

High level of agreement in a fixed vs. live cell-based assay for antibodies to myelin oligodendrocyte glycoprotein in a real-world clinical laboratory setting

IntroductionAs recognition of myelin oligodendrocyte glycoprotein (MOG) antibody-associated disease becomes more widespread, the importance of appropriately ordering and interpreting diagnostic testing for this antibody increases. Several assays are commercially available for MOG testing, and based on a few small studies with very few discrepant results, some have suggested that live cell-based assays (CBA) are superior to fixed CBA for clinical MOG antibody testing. We aimed to determine the real-world agreement between a fixed and live CBA for MOG using two of the most commonly available commercial testing platforms.MethodsWe compared paired clinical samples tested at two national clinical reference laboratories and determined the real-world agreement between the fixed CBA and live CBA.ResultsOf 322 paired samples tested on both platforms, 53 were positive and 246 were negative by both methodologies (agreement 92.9%, Cohen’s kappa 0.78, [0.69-0.86]). Spearman correlation coefficient was 0.80 (p < 0.0001). Of the discrepant results, only 1 of 14 results positive by the live CBA had a titer greater than 1:100, and only 1 of 9 results positive by the fixed CBA had a titer of greater than 1:80. Lower titers on the fixed CBA correlate to higher titers on the live CBA.ConclusionOverall, there is excellent agreement between fixed and live CBA for MOG antibody testing in a real-world clinical laboratory setting. Clinicians should be aware of which method they use to assess any given patient, as titers are comparable, but not identical between the assays

Autoimmune Neurology

Autoimmune neurology is a rapidly developing specialty driven by an increasing recognition of autoimmunity as the cause for a broad set of neurologic disorders and ongoing discovery of new neural autoantibodies associated with recognizable clinical syndromes. The diversity of clinical presentations, unique pathophysiology, and the complexity of available treatments requires a dedicated multidisciplinary team to diagnose and manage patients. In this article, we focus on antibody-associated autoimmune encephalitis (AE) to illustrate broader themes applicable to the specialty. We discuss common diagnostic challenges including the utilizat

Paraneoplastic and Other Autoimmune Encephalitides: Antineuronal Antibodies, T Lymphocytes, and Questions of Pathogenesis

Autoimmune and paraneoplastic encephalitides represent an increasingly recognized cause of devastating human illness as well as an emerging area of neurological injury associated with immune checkpoint inhibitors. Two groups of antibodies have been detected in affected patients. Antibodies in the first group are directed against neuronal cell surface membrane proteins and are exemplified by antibodies directed against the N-methyl-D-aspartate receptor (anti-NMDAR), found in patients with autoimmune encephalitis, and antibodies directed against the leucine-rich glioma-inactivated 1 protein (anti-LGI1), associated with faciobrachial dystonic seizures and limbic encephalitis. Antibodies in this group produce non-lethal neuronal dysfunction, and their associated conditions often respond to treatment. Antibodies in the second group, as exemplified by anti-Yo antibody, found in patients with rapidly progressive cerebellar syndrome, and anti-Hu antibody, associated with encephalomyelitis, react with intracellular neuronal antigens. These antibodies are characteristically found in patients with underlying malignancy, and neurological impairment is the result of neuronal death. Within the last few years, major advances have been made in understanding the pathogenesis of neurological disorders associated with antibodies against neuronal cell surface antigens. In contrast, the events that lead to neuronal death in conditions associated with antibodies directed against intracellular antigens, such as anti-Yo and anti-Hu, remain poorly understood, and the respective roles of antibodies and T lymphocytes in causing neuronal injury have not been defined in an animal model. In this review, we discuss current knowledge of these two groups of antibodies in terms of their discovery, how they arise, the interaction of both types of antibodies with their molecular targets, and the attempts that have been made to reproduce human neuronal injury in tissue culture models and experimental animals. We then discuss the emerging area of autoimmune neuronal injury associated with immune checkpoint inhibitors and the implications of current research for the treatment of affected patients

Anti-Yo antibody uptake and interaction with its intracellular target antigen causes Purkinje cell death in rat cerebellar slice cultures: a possible mechanism for paraneoplastic cerebellar degeneration in humans with gynecological or breast cancers.

Anti-Yo antibodies are immunoglobulin G (IgG) autoantibodies reactive with a 62 kDa Purkinje cell cytoplasmic protein. These antibodies are closely associated with paraneoplastic cerebellar degeneration in the setting of gynecological and breast malignancies. We have previously demonstrated that incubation of rat cerebellar slice cultures with patient sera and cerebrospinal fluid containing anti-Yo antibodies resulted in Purkinje cell death. The present study addressed three fundamental questions regarding the role of anti-Yo antibodies in disease pathogenesis: 1) Whether the Purkinje cell cytotoxicity required binding of anti-Yo antibody to its intraneuronal 62 kDa target antigen; 2) whether Purkinje cell death might be initiated by antibody-dependent cellular cytotoxicity rather than intracellular antibody binding; and 3) whether Purkinje cell death might simply be a more general result of intracellular antibody accumulation, rather than of specific antibody-antigen interaction. In our study, incubation of rat cerebellar slice cultures with anti-Yo IgG resulted in intracellular antibody binding, and cell death. Infiltration of the Purkinje cell layer by cells of macrophage/microglia lineage was not observed until extensive cell death was already present. Adsorption of anti-Yo IgG with its 62 kDa target antigen abolished both antibody accumulation and cytotoxicity. Antibodies to other intracellular Purkinje cell proteins were also taken up by Purkinje cells and accumulated intracellularly; these included calbindin, calmodulin, PCP-2, and patient anti-Purkinje cell antibodies not reactive with the 62 kDa Yo antigen. However, intracellular accumulation of these antibodies did not affect Purkinje cell viability. The present study is the first to demonstrate that anti-Yo antibodies cause Purkinje cell death by binding to the intracellular 62 kDa Yo antigen. Anti-Yo antibody cytotoxicity did not involve other antibodies or factors present in patient serum and was not initiated by brain mononuclear cells. Purkinje cell death was not simply due to intraneuronal antibody accumulation

Macrophage/microglial cells infiltrate the Purkinje cell layer after cell death has already begun.

<p>The Purkinje cell layer is shown at three points in time. Cells of macrophage/monocyte lineage were not detected within the Purkinje cell layer at 48 hours, or at 72 hours, when cell death was already apparent. Macrophage/mononuclear infiltration did not begin until 96 hours (data not shown) and was more extensive at 120 hours. These data indicate that initiation of Purkinje cell death did not involve antibody-mediated cellular cytotoxicity. Scale bar = 20μ.</p

Comparison of uptake and cytotoxicity of anti-Yo antibody versus three other antibodies specific for the intracellular Purkinje cell proteins: calbindin, calmodulin, and PCP-2.

<p>The top row of panels demonstrates uptake and accumulation of IgG (red) within Purkinje cells after 96 hours in cultures incubated with anti-calmodulin, anti-calbindin, anti PCP-2, or anti-Yo IgGs. Entry of SYTOX green into Purkinje cells containing IgG, indicative of cell membrane injury and death (yellow), was seen in only in cultures incubated with anti-Yo IgGs (examples shown by arrows). The lower panels show only SYTOX green staining of Purkinje cells in cultures incubated with the antibodies indicated. In the culture incubated with anti-PCP-2. SYTOX staining indicative of cell death is seen in a single cell outside the Purkinje cell layer (asterisk) but not in Purkinje cells. Cultures were followed through 144 hours. There was progression of cell death in cultures incubated with anti-Yo antibodies. In contrast, cultures incubated calbindin, calmodulin, and PCP-2 did not exhibit Purkinje cell death above background levels seen in controls incubated with normal human IgG (data not shown). Scale bar = 20μ.</p

Rat cerebellar slice culture incubated with serum from Patient 3, a neurologically normal individual with mixed mesodermal ovarian sarcoma.

<p><b>Panels A and B</b> demonstrate. extensive accumulation of IgG not only within Purkinje cells (arrow) but also in other neurons within and near the Purkinje cell layer (asterisks). <b>Panels C and D</b>: Purkinje and other neurons exhibiting Cy5 labeling for human IgG do not contain SYTOX green, indicating that IgG uptake had occurred in viable cells. Scale bars = 20μ.</p