title: Activation of the gut-associated lymphoid tissue with expression of interleukin-2 receptors that peaks during weaning in the rat.
abstract: BACKGROUND
  Weaning exposes the intestinal mucosa to food and bacterial antigens at an age when the immune system is believed to be immature and functionally defective. The purpose of this study was to investigate changes in activation and phenotype of immune cells of the gut-associated lymphoid tissue during weaning.
  
  
  METHODS
  Litters of infant rats were studied from pre- to postweaned life. The activation status, assessed by interleukin-2 receptor (IL-2R) expression, and phenotype of cells in the gut-associated lymphoid tissue were examined by immunostaining.
  
  
  RESULTS
  Interleukin-2 receptor expression peaked two to four-fold at midweaning (day 21) in mesenteric lymph nodes, jejunal lamina propria, Peyer's patches, and intraepithelial lymphocytes, compared with adult animals (day 70). CD45+ cells expanded in the lamina propria, epithelium, and lymphocyte-filled villi. With CD45 as the denominator, 10% to 50% of lymphocytes in the lamina propria and epithelium were alphabetaT-cell receptor (TCR)+, but the remaining cells had a null phenotype, because there were low numbers of gammadeltaTCR+ T cells, B cells, and macrophages. Natural killer cells peaked at midweaning in the lamina propria (9%) and epithelium (20%) but were less than 5% of CD45+ cells after weaning.
  
  
  CONCLUSIONS
  Rather than being immature or functionally inactive, the gut-associated lymphoid tissue reacts appropriately during weaning with expression of IL-2R and expansion of alphabetaTCR+ T-cells.
authors.affiliation: Gastroenterology Unit, The Queen Elizabeth Hospital, Woodville South, South Australia, Australia.
authors.forename: M
authors.initials: M
authors.lastname: Masjedi
authors.forename: D R
authors.initials: DR
authors.lastname: Tivey
authors.forename: F M
authors.initials: FM
authors.lastname: Thompson
authors.forename: A G
authors.initials: AG
authors.lastname: Cummins
mesh_terms: D000818:Animals; D016130:Immunophenotyping; D007413:Intestinal Mucosa / Q000276:immunology; D007422:Intestines / Q000254:growth & development* / Q000276:immunology*; D007583:Jejunum / Q000254:growth & development / Q000276:immunology; D017493:Leukocyte Common Antigens / Q000032:analysis; D008198:Lymph Nodes / Q000378:metabolism; D008214:Lymphocytes / Q000276:immunology; D008221:Lymphoid Tissue / Q000254:growth & development* / Q000276:immunology*; D008643:Mesentery; D010581:Peyer's Patches / Q000254:growth & development / Q000276:immunology; D051381:Rats; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000276:immunology; D015375:Receptors, Interleukin-2 / Q000502:physiology*; D013601:T-Lymphocytes / Q000276:immunology; D014886:Weaning
chemical_list: D016693:Receptors, Antigen, T-Cell, alpha-beta; D015375:Receptors, Interleukin-2; D017493:Leukocyte Common Antigens