title: T-dependent areas in the chicken bursa of Fabricius: an immunohistological study.
abstract: BACKGROUND
  The so-called diffusely infiltrated lymphoid tissue of the chicken bursa of Fabricius was previously described as a T-dependent bursal area.
  
  
  METHODS
  We have analyzed immunohistologically its postnatal development by using a battery of mAbs, most of them raised specifically to chicken T cells, in order to characterize phenotypically the nature of its cell components, appearance, development, and possible functional significance.
  
  
  RESULTS
  Our results demonstrate that this tissue represents poorly developed lymphoid aggregates, the cell content reminiscent of that found in other lymphoid tissues occurring throughout the avian gut. The first lymphoid elements appear in this bursal area only after hatching, growing rapidly to reach the adult condition in the second week of postnatal life. They consist mainly of T lymphocytes, including principally. CD4+ TcR alpha V beta 1+ cells, which form cell groups and CD8+ cells, and TcR gamma delta+ lymphocytes, which predominate in the subepithelial area and within the epithelium. MHC Class II molecule-expressing cells and IgM-, IgG-, and IgA-positive B lymphocytes also occupy the subepithelial region.
  
  
  CONCLUSIONS
  We propose that the bursal diffusely infiltrated lymphoid tissue of the chicken represents gut-associated lymphoid tissue involved in mounting immune responses to antigens that reach the bursal lumen via the cloaca.
authors.affiliation: Department of Cell Biology, Faculty of Biology, Complutense University, Madrid, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Cortés
authors.forename: J
authors.initials: J
authors.lastname: Fonfría
authors.forename: A
authors.initials: A
authors.lastname: Vicente
authors.forename: A
authors.initials: A
authors.lastname: Varas
authors.forename: J
authors.initials: J
authors.lastname: Moreno
authors.forename: A G
authors.initials: AG
authors.lastname: Zapata
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal; D001402:B-Lymphocytes / Q000502:physiology; D002060:Bursa of Fabricius / Q000737:chemistry / Q000166:cytology* / Q000254:growth & development; D002642:Chick Embryo; D002645:Chickens / Q000254:growth & development / Q000276:immunology*; D007150:Immunohistochemistry; D008221:Lymphoid Tissue / Q000166:cytology; D013601:T-Lymphocytes / Q000737:chemistry / Q000502:physiology*
chemical_list: D000911:Antibodies, Monoclonal