IFNG and hypersensitivity: Application of hUC-MSC EVs in a mouse model of contact hypersensitivity (CHS) reduced ear swelling and ear leukocyte infiltration, reduced the percentages of IFN-γ producing CD8+ and CD4+ T cells, increased the levels of T regulatory (Treg) cells in the cervical lymph nodes, and finally, decreased serum levels of IFN-γ and TNF-α while increasing those of IL-10 (Guo et al., 2019).