Fig. 2

ICOSL mediated immunomodulatory of mesenchymal stromal/stem cells (MSCs) on T cells and ILC2. MSCs express a low amount of ICOSL in the naive state. However, the co-culture of MSCs by TCD4⁺ cells in the regulatory T cell-inducing conditions increases ICOSL expression up to tenfold according to qPCR results. Also, this co-culture leads to an increase in the number and percentage of regulatory T cells compared to the culture of TCD4.⁺ cells only under regulatory induction conditions (as the control group). It has been shown that the co-culture of MSCs with PBMCs also leads to the expansion and function of the regulatory T-cell population. The effect of MSCs on ILC2 functions is direct and indirect. In indirect conditions, the co-culture of MSCs with PBMCs suppresses the functions of ILC2 by expanding the population of regulatory T cells and their IL-10 production. Meanwhile, the direct co-cultivation of ILC2 with MSCs increases the functions of ILC2 through ICOS-ICOSL interaction. ILC-2 that have been directly co-cultured with MSCs have a high survival rate and highly produce cytokines such as IL-5, IL-10, and IL-33