Résumé :
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Communication n° 488 Muscle acetylcholine receptor (AChR), the autoantigen in myasthenia gravis, is difficult to be produced in large amounts as an intact molecule. We have successfully expressed soluble extracellular domains (ECDs) of ?, ?, ? and ? AChR subunits in the yeast Pichia pastoris in satisfactory amounts. The ECDs were immobilized on Sepharose beads and were used to immunoadsorb the corresponding autoantibodies from plasmas and sera of myasthenic patients. Isolated autoantibodies are being tested for their ability to cause AChR internalization and degradation (antigenic modulation) in the human cell line TE671. In several experiments the anti-? autoantibodies of two myasthenic plasmas have been found capable of producing significant loss of the receptors (more than 60%). In a set of preliminary experiments the anti-? autoantibodies of the same plasmas, when injected in BALB/C mice, caused weight loss and very mild myasthenic symptoms (grade +/-). We are now planning to isolate larger amounts of autoantibodies to various ECDs and to further characterize them, in order to better understand the pathogenic mechanisms of MG.
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