title: Histological development of the thymic and intestinal lymphoid tissue of the horse.
abstract: The basic components of the immune system, and the defence mechanisms in the gastrointestinal tract, are briefly reviewed. Histological studies in 84 equine foetuses showed that lymphoid cells begin populating the thymic primordium at 11-12 weeks, the mesenteric lymph nodes at 13 weeks, the spleen at 25 weeks and the intestinal lamina propria at 13-14 weeks' gestation. Lymphocytes were seen in the intestinal epithelium very early in gestation. Histological signs of response to antigenic stimulation were seen in five foetuses, indicating that the horse is likely to be capable of mounting an immune response in utero. The changing status of the foal as it becomes fully immunocompetent is discussed.
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology; D003126:Colostrum / Q000276:immunology; D004064:Digestive System / Q000276:immunology; D004804:Eosinophils / Q000276:immunology; D005260:Female; D005333:Fetus / Q000033:anatomy & histology / Q000276:immunology; D006736:Horses / Q000033:anatomy & histology* / Q000276:immunology; D007071:Immunoglobulin A, Secretory; D007422:Intestines / Q000166:cytology*; D007583:Jejunum / Q000033:anatomy & histology; D008198:Lymph Nodes / Q000166:cytology / Q000276:immunology; D008221:Lymphoid Tissue / Q000254:growth & development*; D011247:Pregnancy; D013154:Spleen / Q000166:cytology / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology; D013950:Thymus Gland / Q000166:cytology / Q000254:growth & development* / Q000276:immunology
chemical_list: D007071:Immunoglobulin A, Secretory