Article Text
Abstract
Background: Id2, an inhibitor of basic helix-loop-helix transcription factors, regulates cell differentiation. Id2−/− mice exhibit a variety of phenotypes in the immune system.
Aims: In this study we investigated whether Id2 plays a role in intestinal intraepithelial lymphocytes (IELs), which constitute the main defence against pathogens in the intestinal tract.
Methods: Flow cytometry and bone marrow transplantation were used to analyse and characterise subsets of IELs of Id2−/− mice. Gene expression was analysed by real-time polymerase chain reaction. Intestinal barrier function was evaluated by treating mice with 5-fluorouracil (5-FU).
Results: Among the four members of the Id gene family, Id2 was selectively expressed in all T cell subsets in the small intestinal IELs. Id2−/− mice showed alteration in the proportions of T cell subsets and a substantial reduction in the number of IELs, especially those of the CD4+ and CD8αβ+ T cell subsets, indicating a more pronounced effect on thymus derived IELs. Expression of αE integrin was reduced in CD4+ and CD8αβ+ T cell subsets in IELs of Id2−/− mice. IELs isolated from C57BL/6 mice reconstituted with Id2−/− bone marrow cells showed a similar phenotype to that of Id2−/− mice, indicating that the defects are intrinsic to bone marrow derived cells. Expression of genes encoding intestinal epithelial cell derived cytokines was reduced in Id2−/− mice. The 5-FU treatment revealed impaired intestinal barrier function of Id2−/− mice.
Conclusions: The Id2 gene is essential for constituting the intestinal mucosal barrier, particularly with respect to IELs. Id2 null mutant mice may provide a good experimental model for studying the ontogeny of IELs and intestinal inflammation and infection.
- Id2 mice
- intestinal intraepithelial lymphocytes
- lamina propria lymphocytes
- mucosal immunity
- small intestine
- bHLH, basic helix-loop-helix
- IELs, intestinal intraepithelial lymphocytes
- LPLs, lamina propria lymphocytes
- IECs, intestinal epithelial cells
- RT-PCR, reverse transcription-polymerase chain reaction
- TCR, T cell receptor
- IL, interleukin
- TGF-β, transforming growth factor β
- IFN-γ, interferon γ
- FCS, fetal calf serum
- PBS, phosphate buffered saline
- FITC, fluorescein isothiocyanate
- PE, phycoerythrin
- mAb, monoclonal antibody
- 5-FU, 5-fluorouracil
- SCF, stem cell factor