CD8ab+ gd T Cells: A Novel T Cell Subset with a Potential Role in Inflammatory Bowel Disease
gd T cells have been attributed a wide variety of functions, which in some cases may appear as contradictory. To better understand the enigmatic biology of gd T cells it is crucial to define the constituting subpopulations. gd T cells have previously been categorized into two subpopulations: CD8aa+ and CD8 cells. In this study we have defined and characterized a novel subset of human gd T cells expressing CD8ab. These CD8ab+ gd T cells differed from the previously described gd T cell subsets in several aspects, including the degree of enrichment within the gut mucosa, the activation status in blood, the type of TCRd variant used in blood, and small but significant differences in their response to IL 2 stimulation. Furthermore, the novel subset expressed cytotoxic mediators and CD69, and produced IFN g and TNF a. In patients with active inflammatory bowel disease the mucosal frequencies of CD8ab+ gd T cells were significantly lower as compared with healthy controls, correlated negatively with the degree of disease activity, and increased to normal levels as a result of anti TNF a therapy. In conclusion, our results demonstrate that CD8ab+ gd T cells constitute a novel lymphocyte subset, which is strongly enriched within the gut and may play an important role in gut homeostasis and mucosal healing in inflammatory bowel disease.
The Journal of Immunology