Immunoregulatory functions of mucosal gammadelta T cells

Heterogeneity of avian gammadelta T cells

gammadelta T cells are distinct with respect to tissue localisation, phenotype and biological functions and similarities between species are not very apparent. To elucidate local and functional heterogeneity of non-stimulated avian gammadelta T cells, the CD8-characterised gammadelta T cell subsets [CD8alpha(+high) (CD8alphaalpha(+) and CD8alphabeta(+)); CD8alpha(+dim); CD8(-)] of blood, spleen and caecum were flow cytometrically quantified and analysed for proliferation state as well as sorted for determination of immune-relevant gene expression by quantitative real-time RT-PCR. The number of avian CD8-characterised gammadelta T cell subsets differed in dependence on tissue and age of bird. Compared to blood and spleen, caecum showed the highest percentage of gammadelta T cells as well as of the CD8alpha(+high) gammadelta T cell subset in 7-week-old birds. Generally, the CD8alphabeta(+) cells significantly outnumbered the CD8alphaalpha(+) lymphocytes within the CD8alpha(+high) gammadelta T cell population of all organs. Additionally, the splenic CD8alphabeta(+) subpopulation revealed the highest proliferation activity. By RT-PCR, mRNA expression of immune-relevant genes was proved in non-stimulated gammadelta T cell subsets, but on different levels. Generally, both CD8alpha(+high) cell subsets (CD8alphaalpha(+) and CD8alphabeta(+)) of blood and spleen showed elevated expression levels for Fas ligand (FasL), XCL1 (lymphotactin) and interferon-gamma (IFNgamma) compared to the CD8alpha(-) gammadelta T cell subset. In contrast, all caecal gammadelta T cell subsets showed similar high levels of these transcripts. Notably, the CD8alphaalpha(+) cells of all locations showed unique expression of TLR4 and interleukin (IL)-2. The results demonstrated that avian gammadelta T cells are not only heterogeneous concerning their CD8 antigen characteristics and tissue localisation, but also with regard to functional features such as proliferation and mRNA expression.

The Role of Cryptopatch-Derived Intraepithelial Lymphocytes in the Development of Chronic Ileocecitis

Lympho-haemopoietic progenitors residing in murine gut cryptopatches (CPs) have been shown to generate intestinal extrathymic intraepithelial lymphocytes (IELs). However, the role of CPs in the development of intestinal inflammation remains unclear. To investigate the role of CPs in the development of intestinal inflammation, we examined SAMP1/Yit mice, which spontaneously develop a chronic intestinal inflammation localized to the terminal ileum and cecum. Here, we showed the sharp correlation between the disease onset and the decreased number of CPs, resulting in decreased number of both thymus-independent IELs including T-cell receptor gammadelta+ (TCRgammadelta+) and CD8alphaalpha+TCRalphabeta+ cells but not thymus-dependent CD8alphabeta+TCRalphabeta+ and CD4+TCRalphabeta+ cells in SAMP1/Yit mice. These data provide the first suggestion that thymus-independent IELs derived from CP might play protective role against the onset and the development of intestinal inflammation.

Regulation of murine inflammatory bowel disease by CD25+ and CD25- CD4+ glucocorticoid-induced TNF receptor family-related gene+ regulatory T cells

CD4(+)CD25(+) regulatory T cells in normal animals are engaged in the maintenance of immunological self-tolerance and prevention of autoimmune disease. However, accumulating evidence suggests that a fraction of the peripheral CD4(+)CD25(-) T cell population also possesses regulatory activity in vivo. Recently, it has been shown glucocorticoid-induced TNFR family-related gene (GITR) is predominantly expressed on CD4(+)CD25(+) regulatory T cells. In this study, we show evidence that CD4(+)GITR(+) T cells, regardless of the CD25 expression, regulate the mucosal immune responses and intestinal inflammation. SCID mice restored with the CD4(+)GITR(-) T cell population developed wasting disease and severe chronic colitis. Cotransfer of CD4(+)GITR(+) population prevented the development of CD4(+)CD45RB(high) T cell-transferred colitis. Administration of anti-GITR mAb-induced chronic colitis in mice restored both CD45RB(high) and CD45RB(low) CD4(+) T cells. Interestingly, both CD4(+)CD25(+) and CD4(+)CD25(-) GITR(+) T cells prevented wasting disease and colitis. Furthermore, in vitro studies revealed that CD4(+)CD25(-)GITR(+) T cells as well as CD4(+)CD25(+)GITR(+) T cells expressed CTLA-4 intracellularly, showed anergic, suppressed T cell proliferation, and produced IL-10 and TGF-beta. These data suggest that GITR can be used as a specific marker for regulatory T cells controlling mucosal inflammation and also as a target for treatment of inflammatory bowel disease.

The puzzling world of murine T regulatory cells

T regulatory cells are essential for downregulation of undesired immune responses and prevention of autoimmune diseases, organ rejection, and graft versus host disease. This review describes the considerable progress made in the recent years in the characterization of the many subsets that constitute the puzzled world of murine T regulatory cells.