title: Biological implications of thymectomy for myasthenia gravis.
abstract: Myasthenia gravis (MG) is an autoimmune disease mediated by autoantibodies to the striated muscle tissue. It is often treated by thymectomy. We review recent studies to investigate the biological implications of thymectomy. In anti-acetylcholine receptor antibody (anti-AchR Ab)-positive patients without a thymoma, abnormal germinal center formation in the thymus seems to play an essential role in the pathogenesis of MG. Specific differentiation of B cells producing anti-AchR Ab takes place uniquely in the thymus, and thymectomy is thought to assist in terminating the provision of high-affinity anti-AchR antibody-producing cells to peripheral organs. Thymectomy is not indicated for anti-AchR Ab-negative MG patients who are antimuscle specific kinase antibody (anti-MuSK Ab)-positive, although some anti-MuSK Ab-negative patients may benefit from the procedure. A thymoma can be considered as an acquired thymus with insufficient function of negative selection. The resection of a thymoma is thought to terminate the production of self-reactive T cells. Thus, the biological implications of thymectomy for MG have been partially revealed. Nevertheless, additional studies are needed to elucidate the ontogeny of T cells that recognize AchR and the mechanism of the activation of anti-AchR antibodies producing B cells.
authors.affiliation: Department of General Thoracic Surgery, Osaka University Graduate School of Medicine, (L-5), 2-2 Yamada-oka, Suita, Osaka, Japan.
authors.forename: Meinoshin
authors.initials: M
authors.lastname: Okumura
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Inoue
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Kadota
authors.forename: Akio
authors.initials: A
authors.lastname: Hayashi
authors.forename: Toshiteru
authors.initials: T
authors.lastname: Tokunaga
authors.forename: Takashi
authors.initials: T
authors.lastname: Kusu
authors.forename: Noriyoshi
authors.initials: N
authors.lastname: Sawabata
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Shiono
mesh_terms: D000328:Adult; D000367:Age Factors; D001323:Autoantibodies; D001402:B-Lymphocytes / Q000276:immunology; D016572:Cyclosporine / Q000627:therapeutic use; D006801:Humans; D007166:Immunosuppressive Agents / Q000627:therapeutic use; D009157:Myasthenia Gravis / Q000188:drug therapy / Q000276:immunology* / Q000601:surgery*; D020794:Receptor Protein-Tyrosine Kinases; D011950:Receptors, Cholinergic; D011978:Receptors, Nicotinic / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology*; D016559:Tacrolimus / Q000627:therapeutic use; D013934:Thymectomy; D013945:Thymoma / Q000276:immunology* / Q000601:surgery; D013950:Thymus Gland / Q000276:immunology
chemical_list: D001323:Autoantibodies; D007166:Immunosuppressive Agents; D011950:Receptors, Cholinergic; D011978:Receptors, Nicotinic; D016572:Cyclosporine; C095714:MUSK protein, human; D020794:Receptor Protein-Tyrosine Kinases; D016559:Tacrolimus