Introduction: Myasthenia gravis (MG) is an autoimmune neuromuscular disorder caused by autoantibodies against the acetylcholine receptor (AChR), leading to impaired synaptic transmission and muscle fatigue. Conventional immunosuppressants like corticosteroids and anti-CD20 antibodies can reduce symptoms but increase infection and malignancy risks due to broad immune suppression. Chimeric autoantibody receptor T (CAAR-T) cell therapy offers a targeted approach by eliminating autoreactive B cells while preserving immune function.
Methods and Results: We designed AChR-CAAR-T cells by fusing the AChR α-subunit extracellular domain with CD137 and CD3ζ signaling modules, using either CD8α or CD28 transmembrane domains (TMDs). In vitro assays with anti-AChR BCR-expressing Nalm-6 cells showed that both constructs effectively eliminated target cells. However, CD8α-TMD CAAR-T cells showed low surface expression, improved slightly by lysosomal inhibition, indicating possible degradation. In contrast, CD28-TMD CAAR-T cells maintained stable surface levels and exhibited stronger cytotoxicity. In vivo, CD28-TMD CAAR-T cells led to more efficient depletion of autoreactive B cells in immunodeficient mice.
Conclusion: This study demonstrates that the choice of transmembrane domain (TMD) critically influences CAAR surface expression and therapeutic efficacy, with CD28-TMD AChR-CAAR-T cells offering superior stability and function as a targeted immunotherapy for AChR-positive MG.