Biology subjects

Thaler, F.

Publications and source records attributed to Thaler, F..

3 recordsLinked to original sources

bioRxiv2025

CSF single-cell RNA sequencing reveals clonally expanded CD4+ stem cell-like memory T cells in GAD65-antibody associated neurological syndromes

BackgroundGlutamic acid decarboxylase (GAD) antibody-associated autoimmune neurological syndromes (AINS) are a spectrum of autoimmune-mediated CNS disorders. While antibodies targeting the 65 kDa isoform of GAD are of high diagnostic value, T cell mediated cytotoxicity has been identified as a key component of disease pathogenesis. The precise pathophysiological mechanisms by which the disease is triggered and maintained, however, remain incompletely understood. MethodsWe performed single-cell transcriptome and immune repertoire sequencing (sc-seq) in CSF and blood of 8 anti-GAD65 AINS patients compared to 8 non-inflammatory controls. Monoclonal antibodies (mAbs) were synthesized from B cell receptor (BCR) data to evaluate the B cellular immune response. FindingsWe identified an increase and expansion of activated CD4+ stem cell-like memory T cells (TSCM) in the CSF of anti-GAD65 AINS patients. Expanded T cells showed increased expression of proinflammatory genes. The mAb analysis revealed a high frequency of GAD65-reactive BCRs in the CSF of anti-GAD65 AINS patients with increased somatic hypermutations compared to non-GAD-reactive BCRs and BCRs from controls. ConclusionsSc-seq identified clonally expanded CD4+ TSCM in the CSF of anti-GAD65 AINS patients harboring cytotoxic properties likely contributing to disease pathogenesis. GAD-reactive B cells circulate in the CSF of anti-GAD65 AINS patients further supporting the concept of an antigen-specific intrathecal immune response. Future studies need to clarify the actual pathogenicity of these immune cells and the link between T and B cellular immune mechanisms in the pathogenesis of anti-GAD65 AINS. FundingGerman Research Foundation (ERARE18-202 UltraAIE), German Federal Ministry of Education and Research (CONNECT GENERATE (2.0); 01GM1908A and 01GM2208A).

immunology↗

bioRxiv2024

Neuropathic pain and distinct CASPR2 autoantibody IgG subclasses drive neuronal hyperexcitability

Patients with autoantibodies (aAbs) against the contactin-associated protein-like 2 (CASPR2) suffer from a variety of clinical syndromes including neuropathic pain, in some patients even as the only symptom. CASPR2 is an adhesion protein of the neurexin IV family and part of the voltage-gated potassium channel complex (VGKC) in neurons of dorsal root ganglia (DRG). The subsequent pathological mechanisms following the binding of CASPR2 aAbs and their association with pain are only partially understood. CASPR2 aAbs are mainly of the IgG4 subclass. Previous studies have neglected subclass-dependent effects. Here we investigated 49 subclassified patient serum samples positive for CASPR2 aAbs. To unravel underlying molecular mechanisms, we used a combination of super-resolution lattice structural illumination microscopy (SIM2) and functional readouts by calcium imaging and electrophysiological recordings. CASPR2-positive patient sera subclassified in IgG4 together with at least one other IgG subclass (IgGX) and patients with only IgG4 were further subdivided into the pain and no pain group. Patient subclassification shed further light on the pathological mechanisms of CASPR2 aAbs. A decrease of CASPR2 expression after long-term exposure to CASPR2 aAbs was only observed for the patient group without pain. Upon withdrawal of the CASPR2 aAbs, CASPR2 expression returned to normal level. Structural alterations were obtained by increased distances between CASPR2 and associated potassium channels along DRG axons using high-resolution lattice SIM2 microscopy but only following binding of CASPR2 aAbs from patients with pain. Similarly, CASPR2 aAbs of patients with pain significantly increased overall neuronal excitability of cultured DRG neurons as measured by calcium imaging. Patch-clamp recordings revealed significantly decreased current amplitudes of voltage-gated potassium (Kv) channels after incubation with all four CASPR2 aAbs subclassifications with the most prominent effect of serum samples harboring IgG4 aAbs. Notably, a patient serum sample lacking IgG4 did not alter Kv channel function. Withdrawal of aAbs rescued Kv channel function to normal levels suggesting that the affected potassium channel function is rather due to a functional block of the VGKC rather than altered structural integrity of the VGKC. Taken together, we found IgG4 aAbs to be a major modifier of potassium channel function. The increase in DRG excitability is primarily due to impaired Kv channel conductance as a consequence of CASPR2 aAbs binding but additional and so far unidentified signal pathways contribute to this process in patients with neuropathic pain.

neuroscience↗

bioRxiv2022

Single-cell RNA sequencing analyses of primary cutaneous B-cell disorders reveal distinct molecular patterns consistent with clinical behavior

Primary cutaneous B-cell lymphomas comprise a heterogeneous group of extranodal non-Hodgkin lymphomas. While primary cutaneous diffuse large B-cell lymphoma leg type (pcDLBCL-LT) is highly aggressive, the two other subtypes, primary cutaneous follicle centre lymphoma (pcFCL) and primary cutaneous marginal zone lymphoma (pcMZL), usually follow an indolent course. To better understand the molecular landscape of these entities, we performed single-cell RNA sequencing of pcFCL, pcMZL, and pcDLBCL-LT skin lesions and compared them to B-cell rich lymphoid proliferation (rB-LP) lesions, gastric MALT lymphoma, nodal FCL, and nodal DLBCL. Our data show that these lymphomas can be clearly distinguished from each other on a transcriptomic level based on scRNA-seq. pcMZL, pcFCL, and rB-LP all exhibited a persistent germinal centre reaction as evidenced by the presence of required support cells and continuous somatic hypermutation within the expanded clone. By contrast, malignant clones of pcDLBCL-LT and gastric MALT lymphoma lesions lacked these features. Further, pcMZL top expanded clones were developing within lesions from naive and not post-germinal centre B cells as currently presumed. Therefore, pcMZL may represent a non-malignant reaction against a yet to be determined antigen. Conversely, in pcFCL, B cells showed a larger amount of clonal expansion. The lack of further differentiation of these B cells may explain its indolent clinical course. In contrast to pcDLCBL-LT, our data thus indicate that pcMZL and pcFCL, similar to rB-LP are characterised by a functional germinal centre reaction likely driven by (a yet unknown) antigen recognition, which supports the classification of pcMZL as a lymphoproliferative disease. Key pointsO_LIIndolent B cell neoplasms are uniquely characterised by ongoing, antigen-driven germinal centre reactions. C_LIO_LIPrimary cutaneous B cell lymphomas are distinct entities compared to their systemic counterparts. C_LI

cancer biology↗