Moreover, loss of CD28 is associated with various immune disorders.24–27 We observed that CD28 expressed on CD4+ T cells, naïve T cells, NKT cells, CD4+ memory T cells, and Treg cells were remarkably enhanced after MSC infusion on days 2 and 4, suggesting that MSCs can promote T cell activation (Fig. 3c). Here, CD4 is linked to immune system disorder.