CD4 and graft versus host disease: After transplantation into murine and humanized murine recipients, a portion (5%–20%) of PSGL1hiCD4+ T cells differentiated into PSGL1loCD4+ Trm cells in an IL-6-Stat3-dependent manner (47) because Stat3 deficiency in the CD4+ T cells and administration of blocking anti-IL-6R mAb markedly reduced the expansion of PSGL1loCD4+ T cells in the GVHD target tissues of murine recipients (47).