Expression of extracellular domains of muscle specific kinase (MuSK) and use as immunoadsorbents for the development of an antigen-specific therapy.

Antibodies against MuSK seem to be the pathogenic factor in approximately 5-8% of myasthenia gravis (MG) patients. We aim to develop an antigen-specific therapy in which only MuSK antibodies will be removed from patients' plasma using MuSK extracellular domain (MuSK-ECD) as immunoadsorbent. We showed that two different immunoadsorbents, very efficiently and selectively depleted the MuSK antibodies from all tested sera, were stable during the procedure and were reusable. Furthermore, animal experiments showed that the treatment has no toxic effects to the animals. We conclude that the MuSK-ECD-mediated immunoadsorption can be used as an efficient antigen-specific therapy for MuSK-MG.