title: Marked increase in CD44-highly positive cells in hyperplastic thymuses from patients with Myasthenia gravis.
abstract: To investigate the role of the thymus in the pathogenesis of myasthenia gravis (MG), immunohistochemical expression of CD44, CD45R0, B7-1, and IL-2 was studied in: (1) hyperplastic thymuses of patients with MG whose symptoms markedly improved after thymectomy, (2) remnant thymuses of patients with MG whose symptoms did not respond to thymectomy, and (3) non-MG control thymus. Lymphocytes strongly expressing CD44, a marker for homing lymphocytes and activated memory lymphocytes in adults, were much more frequently observed in hyperplastic MG thymuses than in remnant thymuses and non-MG control thymuses. These CD44-highly positive cells in hyperplastic MG thymuses were for the most part located in the subcapsular and cortical areas but also occasionally in medullary areas. Some of these CD44-highly positive cells coexpress CD45R0. CD44-highly positive cells were located in the vicinity of blood vessels and thus appeared to have migrated directly from extralobular blood vessels. B7-1-positive cells and interleukin (IL)-2-positive cells were also more abundant in the MG patients than in controls and were localized in the proximity of CD44-highly positive cells. These findings suggest that mature T and B cells recirculate into hyperplastic MG thymus via CD44-associated mechanisms and are activated there.
authors.affiliation: Department of Neurology, Iwate Medical University, Uchimaru 19-1, Morioka 020, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Utsugisawa
authors.forename: Y
authors.initials: Y
authors.lastname: Nagane
authors.forename: H
authors.initials: H
authors.lastname: Tohgi
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D015703:Antigens, CD / Q000032:analysis; D018122:B7-1 Antigen / Q000032:analysis; D017252:CD3 Complex / Q000032:analysis; D005260:Female; D006801:Humans; D018960:Hyaluronan Receptors / Q000032:analysis*; D006965:Hyperplasia; D007150:Immunohistochemistry; D007376:Interleukin-2 / Q000032:analysis; D017493:Leukocyte Common Antigens / Q000032:analysis; D008297:Male; D008875:Middle Aged; D009157:Myasthenia Gravis / Q000276:immunology* / Q000473:pathology / Q000601:surgery; D012016:Reference Values; D013934:Thymectomy; D013950:Thymus Gland / Q000166:cytology / Q000276:immunology* / Q000473:pathology*
chemical_list: D015703:Antigens, CD; D018122:B7-1 Antigen; D017252:CD3 Complex; D018960:Hyaluronan Receptors; D007376:Interleukin-2; D017493:Leukocyte Common Antigens