title: Increased HLA-DR and decreased CD3 on human intestinal intraepithelial lymphocytes: evidence of activation?
abstract: BACKGROUND
  Activation of circulating T lymphocytes results in expression of HLA-DR, interleukin-2 receptor (IL-2R), transferrin receptor (TrR), and decreased amounts of surface CD3.
  
  
  OBJECTIVE
  To examine the activation status of human intestinal intraepithelial lymphocytes (IELs) by flow cytometry.
  
  
  METHODS
  Duodenal biopsy specimens from 12 patients provided a source of intestinal lymphocytes. Dual colour analysis was used to compare activation marker expression by IELs with peripheral blood (PB) T lymphocytes from the same patients.
  
  
  RESULTS
  All human IEL populations express HLA-DR and their density of expression is lower than on the small population of HLA-DR+ resting PB T lymphocytes (mean fluorescence intensity (MFI) 52.9, range 19.8-94.8 v 152.6 range, 49.1-320.3; p < 0.01). The density of CD3 was significantly reduced on IELs (MFI 465.8, range 228.7-660), compared with PB T lymphocytes (756.3, range 444.5-1573.7; p < 0.009). IL-2R was not detected on IELs; nor were the activation markers, TrR, M21 C5, or M2 B3.
  
  
  CONCLUSIONS
  HLA-DR expression on IELs together with decreased CD3 expression suggest previous stimulation. However, the absence of additional markers of T cell activation may reflect a unique pathway of activation.
authors.affiliation: Department of Immunology, St Jame's Hospital, Dublin, Ireland.
authors.forename: M
authors.initials: M
authors.lastname: Abuzakouk
authors.forename: D
authors.initials: D
authors.lastname: Kelleher
authors.forename: C
authors.initials: C
authors.lastname: Feighery
authors.forename: C
authors.initials: C
authors.lastname: O'Farrelly
mesh_terms: D000328:Adult; D000368:Aged; D017252:CD3 Complex / Q000032:analysis*; D002469:Cell Separation; D004386:Duodenum / Q000276:immunology*; D005260:Female; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D006684:HLA-DR Antigens / Q000032:analysis*; D006801:Humans; D007413:Intestinal Mucosa / Q000276:immunology; D008213:Lymphocyte Activation; D008297:Male; D008875:Middle Aged; D016176:T-Lymphocyte Subsets / Q000276:immunology*
chemical_list: D017252:CD3 Complex; D006684:HLA-DR Antigens