The Impact of IFN-γ Licensing on Mesenchymal Stromal Cells' Mediated Immunoregulation and HLA Class II Expression: Emerging Evidence from In Vitro Results.

Mesenchymal stromal cells (MSCs) exert their immunoregulatory properties after licensing by inflammatory signaling cues, e.g., interferon (IFN)-γ. However, MSCs licensing by IFN-γ may result in increased expression of human leukocyte antigen (HLA) class II, which is related to rapid cell elimination, impairment of their immunosuppressive properties, and patient sensitization. The aim of this study was to evaluate the impact of IFN-γ on mediated immunoregulation and HLA class II expression. In this study, Wharton's jelly (WJ) MSCs were isolated from human umbilical cords. Well-defined WJ-MSCs were submitted to IFN-γ exposure, and after 96 h, evaluation of biomolecule secretion and HLA class II expression was performed. Typing of HLA alleles using a next-generation sequencing (NGS) platform was performed. IFN-γ-primed WJ-MSCs secreted a high amount of immunoregulatory biomolecules, while elevated expression of HLA-DRB1 was observed. Analyses the NGS results showed the possibility of WJ-MSCs cluster formation based on their frequency of detected HLA alleles and immunoregulatory potential. Taking into consideration that IFN-γ-primed WJ-MSCs express HLA class II alleles, it is suggested that the HLA histocompatibility between allogeneic donor and recipient should be strongly considered to acquire the most beneficial outcome for the MSCs therapeutic strategy.