Reply: "Function of Cryopreserved Mesenchymal Stromal Cells With and Without Interferon-γ Prelicensing Is Context Dependent".

Freshly thawed mesenchymal stromal cells (MSCs) transiently display altered cell physiology and a recent report by Chinnadurai et al. [Stem Cells 2016;34:2429-2442] demonstrated that thawed allogeneic MSCs are also susceptible to T-cell mediated lysis in vitro and that this effect can be mitigated by activating MSCs with IFN-γ prior to freeze and thaw. In the letter to the editor by Ankrum et al., "Function of Cryopreserved MSCs with and without IFN-γ pre-licensing is Context Dependent," the author provide data that IFN-γ pretreatment of human MSCs before cryobanking fails to enhance their potency post thaw in a mouse model of retinal disease. Considering that the experimental set up involves the use of human MSCs in mice with normal immune systems, we propose that IFN-γ MSC activation enhances the immune incompatibility of xenogenic human cells in a manner which may confound the predictive value for human translational use. Stem Cells 2017;35:1440-1441.