IL-2 promotes the subset restoration of intraepithelial lymphocytes after ischemia/reperfusion injury

Role of the intestinal cytokine microenvironment in shaping the intraepithelial lymphocyte repertoire

Local resident IELs are composed of distinct subsets of T cells with potent cytolytic and immunoregulatory capacities. As IELs are located within this unique interface between the core of the body and the outside environment, the specific development and function of intestinal IELs must be tightly regulated. To accomplish this, the cytokine microenvironment of the intestine has evolved sophisticated mechanisms that modulate the phenotype, ontogeny, and function of these cells. In this review, we summarize the evidence demonstrating the origin of certain intestinal cytokines, including IL-7, IL-15, IL-2, TGF-β, and SCF and discuss what influence such cytokines may have on IELs. Moreover, we review data suggesting that the abnormal expression of cytokines that leads to the heightened activation of IELs may also contribute to immunopathological responses or exacerbate inflammatory diseases, such as IBD and celiac disease, or promote cancer development and progression.

Effects of intraepithelial lymphocyte-derived cytokines on intestinal mucosal barrier function

The mucosal surface of the gastrointestinal tract directly interacts with the mucosal lumen, which is continuously exposed to foreign antigens. Specialized intraepithelial lymphocytes (IELs), located between the basolateral surfaces of the epithelial cells, are important as the first line of defense against microbes as well as for their role in the maintenance of epithelial barrier homeostasis. Although IELs are mainly composed of T cells, they are phenotypically and functionally distinct from T cells in peripheral blood or the spleen. Not only are IELs stimulated by the antigens of the intestinal lumen but are they also stimulated by regulatory immune cells. The integrity of the intestinal mucosal barrier is closely tied to the IEL function. Cytokines produced by IELs modulate the cellular functions that trigger the downstream signaling pathways and mediate the barrier homeostasis. In this review, we will address the broad spectrum of cytokines that are derived from IELs and the functional regulation of these cytokines on the intestinal barrier.

Treadmill exercise in mice increases intestinal lymphocyte loss via apoptosis

Strenuous exercise is associated with a transient decline in circulating lymphocytes, possibly through increased apoptosis. Intestinal lymphocytes are important effector cells of intestinal immune function but have not been studied in relation to exercise.

AIM

The purpose of the present study was to examine the effect of exercise on intestinal lymphocyte phenotypes and apoptosis.

METHODS

Female C57BL/6 mice (n = 112) were randomized to: (1) treadmill running (90 min, 32 m min-1, 8 degrees grade) and killed immediately after exercise, (2) treadmill running and killed 2 h after exercise, (3) treadmill running and killed 24 h after exercise or (4) a non-exercised control condition with exposure to treadmill noise and vibration without running.

RESULTS

Flow cytometry indicated that the total intestinal CD3+T (P < 0.01), CD4+T (P < 0.005), CD8+T (P < 0.05), pan-NK (P < 0.005) and CD19+B (P < 0.05) lymphocytes were significantly lower 24 h after exercise compared with non-exercised controls. Significantly more CD3+T (P < 0.05) and CD8+T (P < 0.05) intestinal lymphocytes stained positive for annexin V, a marker of apoptosis, at 24 h after exercise compared with intestinal lymphocytes from non-exercised controls. Plasma corticosterone and 8-isoprostane concentrations were also significantly higher immediately after exercise compared with other exercise conditions.

CONCLUSION

Acute strenuous exercise increases intestinal T (CD3+ and CD8+) lymphocyte loss and apoptosis. The extent to which the exercise-induced apoptosis in intestinal lymphocytes is mediated by increased glucocorticoid concentrations in the gastrointestinal tract will require further studies.