CD274 and graft versus host disease: More recently, using multiple GVHD models (two murine allogeneic HCT models and a human → mouse xenogeneic HCT model), Ni et al. (58) showed that CD4+ T cell depletion increased serum IFN-γ levels, leading to an upregulation of PD-L1 in recipient tissues and donor CD8+ T cells.