HLA-G DIMER PROLONGS KIDNEY ALLOGRAFT SURVIVAL BY INHIBITING CD8+T CELL ACTIVATION AND GRANZYME B EXPRESSION

Abstract

Solid organ transplantation is the preferred therapy for many patients diagnosed with end stage organ failure, however allograft rejection is a significant barrier for graft survival. Patient care involves heavy immunosuppressive drug treatment leading to elevated risk for cancer and other opportunistic infections. Hence there is a need to develop effective alternative approaches to minimize graft rejection. We focused on Human leukocyte antigen G (HLA-G), a nonclassical HLA class Ib molecule critically involved in the maintenance of maternal tolerance to semi-allogeneic fetal tissues during pregnancy and has emerged as a potential therapeutic target to control allograft rejection. We demonstrate here that the level of soluble HLA-G dimer was higher in a group of 90 patients with a functioning renal allograft compared with 40 patients who rejected (RJ) their transplants. The HLA-G dimer level was not affected by demographic status. One of the potential mechanisms in tissue organ allograft rejection involves the induction of granzymes and perforin, which are the main effector molecules expressed by CD8+ cytotoxic T lymphocytes and function to destroy allogeneic transplants. Using genomics, molecular and cellular analyses of cells from T-cell–mediated RJ and nonrejected kidney transplant patients, cells from leukocyte Ig-like receptor B1 (LILRB1) transgenic mice, humanized mice, and genetically engineered HLA-G dimer, we demonstrated a novel mechanism by which HLA-G dimer inhibits activation and cytotoxic capabilities of human CD8+ T cells. This mechanism implicated the downregulation of Granzyme B expression and the essential involvement of LILRB1. Thus, HLA-G dimer has the potential to be a specific and effective therapy for prevention of allograft rejection and prolongation of graft survival.