Mesenchymal Stromal Cells and Natural Killer Cells: A Complex Story of Love and Hate

Mesenchymal stromal cells (MSCs), characterized by both multidifferentiation potential and potent immunomodulatory capacity, represent a promising, safe and powerful cell based-therapy for repairing tissue damage and/or treating diseases associated with aberrant immune responses. Natural killer (NK) cells are granular lymphocytes of the innate immune system that function alone or in combination with other immune cells to combat both tumors and virally infected cells. After their infusion, MSCs are guided by host inflammatory elements and can interact with different immune cells, particularly those of the innate immune system. Although some breakthroughs have been achieved in understanding these interactions, much remains to be determined. In this review, we discuss the complex interactions between NK cells and MSCs, particularly the importance of improving the therapeutic value of MSCs.