Journal Article

Thymus-derived B cell clones persist in the circulation after thymectomy in myasthenia gravis

Pham, Minh C., Lee, Casey S., Kaminski, Henry J., O’Connor, Kevin C., Jacobson, Leslie, Kleinstein, Steven H., Vincent, Angela, Jiang, Ruoyi, Homer, Robert J., Nowak, Richard J., Aban, Inmaculada, Detterbeck, Frank C., Hoehn, Kenneth B.

2020

Overview

Myasthenia gravis (MG) is a neuromuscular, autoimmune disease caused by autoantibodies that target postsynaptic proteins, primarily the acetylcholine receptor (AChR) and inhibit signaling at the neuromuscular junction. The majority of patients under 50 y with AChR autoantibody MG have thymic lymphofollicular hyperplasia. The MG thymus is a reservoir of plasma cells that secrete disease-causing AChR autoantibodies and although thymectomy improves clinical scores, many patients fail to achieve complete stable remission without additional immunosuppressive treatments. We speculate that thymus-associated B cells and plasma cells persist in the circulation after thymectomy and that their persistence could explain incomplete responses to resection. We studied patients enrolled in a randomized clinical trial and used complementary modalities of B cell repertoire sequencing to characterize the thymus B cell repertoire and identify B cell clones that resided in the thymus and circulation before and 12 mo after thymectomy. Thymus-associated B cell clones were detected in the circulation by both mRNA-based and genomic DNA-based sequencing. These antigen-experienced B cells persisted in the circulation after thymectomy. Many circulating thymus-associated B cell clones were inferred to have originated and initially matured in the thymus before emigration from the thymus to the circulation. The persistence of thymus-associated B cells correlated with less favorable changes in clinical symptom measures, steroid dose required to manage symptoms, and marginal changes in AChR autoantibody titer. This investigation indicates that the diminished clinical response to thymectomy is related to persistent circulating thymus-associated B cell clones.

• Publisher: National Academy of Sciences
• Subject: Acetylcholine receptors / Adolescent / Adult / Antigens / Autoantibodies / Autoantibodies - immunology / Autoimmune diseases / B-Lymphocytes - immunology / B-Lymphocytes - metabolism / Biological Sciences / Biomarkers / Circulation / Clonal Evolution - genetics / Clonal Selection, Antigen-Mediated / Disease Susceptibility / DNA sequencing / Emigration / Female / Genomics / Humans / Hyperplasia / Immunology and Inflammation / Lymphocyte Count / Lymphocytes B / Male / Middle Aged / Models, Biological / mRNA / Myasthenia gravis / Myasthenia Gravis - blood / Myasthenia Gravis - etiology / Neuromuscular junctions / Plasma cells / Radioimmunoassay / Receptors, Cholinergic - immunology / Remission / Signs and symptoms / Steroids / Thymectomy / Thymus / Thymus gland / Thymus Gland - cytology / Thymus Gland - immunology / Thymus Gland - metabolism / V(D)J Recombination / Young Adult