How to improve the sensitivity and specificity of cell-based assays in detecting autoantibodies in neuroimmune diseases.

Autoantibodies are associated with neuroimmune diseases that affect the central and peripheral nervous systems. There are many methods for detecting autoantibodies, among which cell-based assay (CBA) is a relatively novel and important technology that is widely used. CBAs, as novel indirect immunofluorescence assays with known antigen epitopes, have revolutionized the identification of autoantibodies compared with the traditional immunoassays, such as the radioimmunoprecipitation and enzyme-linked immunosorbent assays, as well as the tissue-based assays (TBAs). However, the results of the same sample might exhibit obvious differences between different laboratories, or among repeated testing in the same laboratory, which influence the sensitivity and specificity in the diagnostic performance for a specific neuroimmune disease. In this paper, we review the establishment of CBA technology, and discuss potential interfering factors in CBA methods on its sensitivity and specificity for the autoantibodies associated with neuroimmune diseases.

Clinical characteristics of anti-AChR-MuSK-LRP4 antibody-negative myasthenia gravis in China.

INTRODUCTION/AIMS: Descriptions of the clinical characteristics of anti-AChR-MuSK-LRP4 antibody-negative myasthenia gravis (triple-negative myasthenia gravis, TNMG) are lacking in the current literature. Therefore, we investigated the clinical characteristics of TNMG in Chinese patients. METHODS: We retrospectively analyzed 925 patients with MG registered in the Department of Neuroimmunology, Henan Institute of Medical and Pharmaceutical Sciences from January 2015 to March 2021. RESULTS: One hundred six patients diagnosed with TNMG were included in the study. The average age of onset was 32.4 y, with a male-to-female ratio of 1:1. The age of onset showed a bimodal distribution: 0-9 y and 40-49 y. Adult patients were more likely to have weakness of limb and bulbar muscles (p < .05). Thymic hyperplasia was found in 20.2% of the patients. Younger patients were more likely to relapse. The rate of adult early-onset myasthenia gravis reaching complete stable remission and pharmacological remission was 47.6%, and the prognosis was better than that in juvenile-onset myasthenia gravis (p = .019). Older age of onset was the only risk factor for the development of generalized TNMG from ocular TNMG (R = 1.046, p = .002, 95% confidence interval 1.017-1.077). DISCUSSION: This study showed that the clinical characteristics of patients with TNMG varied among the different age groups. Significant findings included a bimodal distribution of onset age, coexisting thymic hyperplasia, and a generally favorable prognosis.

Sorting nexin 17 increases low-density lipoprotein receptor-related protein 4 membrane expression: A novel mechanism of acetylcholine receptor aggregation in myasthenia gravis.

Myasthenia gravis (MG) is characterized by autoimmune damage to the postsynaptic membrane of the neuromuscular junction (NMJ) with impaired postsynaptic acetylcholine receptor (AChR) aggregation. Low-density lipoprotein receptor-related protein 4 (LRP4) plays an important role in AChR aggregation at endplate membranes via the Agrin-LRP4-muscle-specific receptor tyrosine kinase (MuSK) cascade. Sorting nexin 17 (SNX17) regulates the degradation and recycling of various internalized membrane proteins. However, whether SNX17 regulates LRP4 remains unclear. Therefore, we examined the regulatory effects of SNX17 on LRP4 and its influence on AChR aggregation in MG. We selected C2C12 myotubes and induced LRP4 internalization via stimulation with anti-LRP4 antibody and confirmed intracellular interaction between SNX17 and LRP4. SNX17 knockdown and overexpression confirmed that SNX17 promoted MuSK phosphorylation and AChR aggregation by increasing cell surface LRP4 expression. By establishing experimental autoimmune MG (EAMG) mouse models, we identified that SNX17 upregulation improved fragmentation of the AChR structure at the NMJ and alleviated leg weakness in EAMG mice. Thus, these results reveal that SNX17 may be a novel target for future MG therapy.