In search of the origin of the thymus: the thymus and GALT may be evolutionarily related.
The thymus is the major primary immune tissue for the production of functional T lymphocytes in vertebrates. However, its evolutionary origin is unknown. It has recently been shown that the generation of local T cells also occurs in gut-associated lymphoid tissues (GALT). This suggests that the thymus and GALT have similar functions and that they might be evolutionarily related. We discuss the possibility that the thymus may have evolved from mucosa-associated lymphoid tissues (MALT) located in the gill region in early vertebrates. Various facts supporting this proposal are summarized.
Matsunaga
T
T
Department of Immunology, Umeå University, Umeå, SE-901 85, Sweden.
Rahman
A
A
D000818:Animals; D005075:Biological Evolution; D001934:Branchial Region / Q000196:embryology; D002060:Bursa of Fabricius / Q000196:embryology / Q000276:immunology; D002454:Cell Differentiation; D019070:Cell Lineage; D002465:Cell Movement; D017637:Clonal Deletion; D004847:Epithelial Cells / Q000166:cytology; D005399:Fishes / Q000033:anatomy & histology / Q000276:immunology; D005880:Gills / Q000276:immunology; D006801:Humans; D007413:Intestinal Mucosa / Q000196:embryology / Q000276:immunology*; D008221:Lymphoid Tissue / Q000196:embryology / Q000276:immunology; D008954:Models, Biological; D009092:Mucous Membrane / Q000276:immunology; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000378:metabolism; D016692:Receptors, Antigen, T-Cell, gamma-delta / Q000378:metabolism; D013045:Species Specificity; D013601:T-Lymphocytes / Q000166:cytology*; D013950:Thymus Gland / Q000196:embryology / Q000276:immunology; D014714:Vertebrates / Q000033:anatomy & histology* / Q000196:embryology / Q000276:immunology
D016693:Receptors, Antigen, T-Cell, alpha-beta; D016692:Receptors, Antigen, T-Cell, gamma-delta