title: Inhibitory activity of intestinal intraepithelial lymphocytes.
abstract: BACKGROUND
  Intestinal intraepithelial lymphocytes (iIEL) are the first line of lymphoid cells exposed to orally absorbed foreign antigen. Because of this unique position, we hypothesized that the iIEL down-regulates the immune response to foreign antigen to prevent broad sensitization.
  
  
  METHODS
  One-way mixed lymphocyte cultures (MLCs) were performed with Brown Norway (BN) as the responder and irradiated Lewis rats as the stimulator. BN iIEL or control cells (irradiated BN spleen-thymus cells) were added to the MLCs to assess their inhibitory function.
  
  
  RESULTS
  When iIEL cells comprised 0.63% of well volumes, a significant (p < 0.05) decline in MLC proliferation was seen. To determine whether this inhibitory action was mediated by a soluble factor, supernatant from iIEL cultured with irradiated Lewis spleen-thymus cells was added to MLCs and was compared with the addition of culture medium as the control group. The iIEL group proliferated significantly less (p < 0.05) than the control group. To further define the mechanism of action, iIEL-conditioned supernatant was treated with neutralizing antibody to transforming growth factor-beta (25 micrograms/ml) or control immunoglobulin. Treated supernatant was then added to an MLC, resulting in a partial loss of inhibitory action.
  
  
  CONCLUSIONS
  The iIEL appears to significantly suppress a response to allogeneic stimuli via a mechanism mediated by the action of one or more soluble factors. Transforming growth factor-beta may well be one of the mediators of this inhibitory action.
authors.affiliation: Department of Surgery, University of Michigan Medical Center, Ann Arbor, USA.
authors.forename: D H
authors.initials: DH
authors.lastname: Teitelbaum
authors.forename: B
authors.initials: B
authors.lastname: Neideck
authors.forename: J
authors.initials: J
authors.lastname: Lee
authors.forename: R M
authors.initials: RM
authors.lastname: Merion
mesh_terms: D000818:Animals; D000906:Antibodies / Q000276:immunology; D000941:Antigens / Q000276:immunology; D016207:Cytokines / Q000502:physiology; D007413:Intestinal Mucosa / Q000166:cytology / Q000276:immunology*; D007959:Lymphocyte Culture Test, Mixed; D008214:Lymphocytes / Q000276:immunology*; D008233:Lymphotoxin-alpha / Q000276:immunology; D051381:Rats; D011914:Rats, Inbred BN; D011917:Rats, Inbred Lew
chemical_list: D000906:Antibodies; D000941:Antigens; D016207:Cytokines; D008233:Lymphotoxin-alpha