Mesenchymal stromal cells protect tissues from Th1 immune responses via IL‐11 secretion

Mesenchymal stromal cells (MSCs) have been shown to modulate the function of various subsets of T cells such as naïve CD4 + T cells and IFNγ + CD4 + Th1 cells; however, mechanisms underlying this regulation have not been fully deciphered. Our in vitro culture assays demonstrate that MSCs suppress the activation and function of CD4 + T cells by secreting interleukin 11, and neutralization of IL11 abrogates MSC‐mediated suppression of CD4 + T cell function. Moreover, delayed‐type, exogenous supplementation of IL11 significantly suppressed IFNγ + expression by Th1 cells. Th1 and CD8 + cells play central roles in T cell‐mediated tissue damage. Using a murine model of hypersensitivity response to study T cell‐mediated tissue damage, we show that silencing IL11 in MSCs significantly abates the capacity of MSCs to suppress the generation of IFNγ‐secreting CD4 + and CD8 + cells, failing to prevent T cell‐mediated tissue inflammation and tissue damage.