ACETYLCHOLINE-RECEPTOR IN RABBIT THYMUS - ANTIGENIC SIMILARITY BETWEEN ACETYLCHOLINE RECEPTORS OF MUSCLE AND THYMUS

  • 1 January 1980
    • journal article
    • research article
    • Vol. 42  (3) , 463-469
Abstract
The presence and immunological properties of acetylcholine receptor (AChR) in rabbit thymus was examined. Binding of 125I-.alpha. Bungarotoxin (.alpha.BGT) to Triton extract from rabbit thymus was saturable (half saturation value: 10-8 M) and occurred with at least 2 affinities, a high one with a dissociation constant of 1.1 .times. 10-10 M and a low affinity one with a dissociation constant of 2 .times. 10-9 M. The complex formation of 125I-.alpha.BGT-thymus extract was inhibited by both carbamylcholine and D-tubocurarine. The AChR existence in rabbit thymus is indicated. Antibody to AChR which was purified from experimental myasthenic rabbits with Narke AChR-affinity gel and labeled with 125I was used to identify the receptor antigenicity in rabbit thymus. Specific 125I-antibody binding to thymic extract was demonstrated by the DEAE-paper disc assay. Evidently AChR with a similar antigenicity to that of skeletal muscle AChR exist in rabbit thymus. A hypothesis that the primary immunogen in myasthenia gravis may be AChR in thymus and an autoimmune reaction against AChR might be initiated within the thymus gland itself is supported.