Roles of the HLA-G gene and its polymorphisms in renal transplantation

Human leukocyte antigen-G (HLA-G) is a nonclassical major histocompatibility complex (MHC) class Ib molecule that plays a critical role in immune tolerance, primarily by promoting immune escape and inducing T-cell anergy. Early studies of HLA-G focused mainly on its function during pregnancy, where it is essential for maintaining maternal-fetal tolerance. In recent years, accumulating evidence has revealed the broader immunoregulatory functions and mechanisms of HLA-G in a variety of pathological conditions. As a key immunosuppressive molecule, HLA-G has been extensively investigated in the context of organ transplantation. In this review, we summarize the current understanding of the biological functions of HLA-G, with particular emphasis on its genetic polymorphisms, and discuss their immunomodulatory roles in renal allograft rejection and post-transplant infections.