Background: Immune dysregulation is a hallmark of autoimmune diseases of the central nervous system (CNS), characterized by an excessive immune response, and primary CNS tumors (pCNS-tumors) showing a highly immunosuppressive parenchymal microenvironment.
Methods: Aiming to provide novel insights into the pathogenesis of CNS autoimmunity and cerebral tumor immunity, we analyzed the peripheral blood (PB) and cerebrospinal fluid (CSF) of 81 autoimmune limbic encephalitis (ALE), 148 relapsing-remitting multiple sclerosis (RRMS), 33 IDH-wildtype glioma, 9 primary diffuse large B cell lymphoma of the CNS (CNS-DLBCL), and 110 controls by flow cytometry (FC). Additionally, an in-depth immunophenotyping of the PB from an independent cohort of 20 RRMS and 18 IDH-wildtype glioblastoma patients compared to 19 controls was performed by FC combined with unsupervised computational approaches.
Autoimmune limbic encephalitis (ALE) represents a heterogeneous disease associated with antibodies targeting extracellular (ALE) epitopes, intracellular (ALE) epitopes, anti-glutamic acid decarboxylase65 ALE (ALE), and ALE without detectable antibodies (ALE). Combining analysis of cellular parameters, investigated by flow cytometry, and soluble parameters in the blood and cerebrospinal fluid (CSF) from a large cohort of 148 ALE patients (33 ALE, 12 ALE, 28 ALE-GAD65, 37 ALE) in comparison to paradigmatic examples for neuro-inflammatory (51 relapsing remitting MS patients (RRMS)), and neuro-degenerative (34 Alzheimer's disease patients (AD)) diseases revealed discrete immune signatures in ALE subgroups. Identification of ALE-subtype specific markers facilitated classification of rare ALE-associated tumors, which may prompt further diagnostic efforts in clinical practice.
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