PPBP and graft versus host disease: 11 out of the 60 hub genes associated with immunoregulation have not been studied in GVHD, including Rgs1, Fpr2, Ppbp (Cxcl7), S1pr3, Npy, Hebp1, Kng1, Plg, Cxcl16, Ccl9, and Cxcl3. The PPI network among the 11 genes was constructed (Figure S3A).