ABSTRACT
PURPOSE OF REVIEW: The aim of this review is to provide an overview of significance of T helper 17 (Th17) immunity in acute, chronic and antibody-mediated allograft rejection. The role of Th17 immunity in development of de-novo autoimmunity following transplantation is outlined. It will also consider the impact of Th17 immunity on transplantation tolerance. Potential therapies to target Th17 immunity are discussed. RECENT FINDINGS: Interleukin17 (IL-17) is produced by a wide variety of immune and non-immune cells in response to injury. IL-17 production by tubular epithelial cells in response to complement activation in acute antibody-mediated rejection may perpetuate immune injury. Th17-dependent de-novo autoimmunity contributes to chronic allograft rejection. Targeting IL-17 not only inhibits Th17 immunity but also attenuates Th1 immunity by affecting the initial recruitment of immune cells to sites of inflammation and modulates innate and adaptive immune responses that ultimately lead to tissue destruction. SUMMARY: Th17 immunity is now beginning to be appreciated as a set of responses mediated not only by CD4 Th17 cells but a variety of immune cells and a plethora of cytokines that collaborate to mediate immune disorders, including transplant rejection. Development and contribution of de-novo autoimmunity to chronic rejection is increasingly appreciated. The developmental plasticity of Tregs and Th17 cells is a major hurdle to Treg-based cellular therapies for transplantation. Several biologics targeting Th17 immunity are under evaluation for autoimmune disease. It remains to be determined whether these can be used in transplantation to improve outcomes.
Subject(s)
Graft Rejection/immunology , Immunosuppressive Agents/therapeutic use , Interleukin-17/immunology , Th17 Cells/immunology , Transplantation Tolerance/immunology , Transplantation, Homologous/immunology , Acute Disease , Autoimmunity , CD4-Positive T-Lymphocytes/immunology , CD8-Positive T-Lymphocytes/immunology , Chronic Disease , Graft Rejection/prevention & control , Humans , Receptors, Antigen, T-Cell, gamma-delta , T-Lymphocytes, Regulatory/immunology , Th17 Cells/drug effects , Transplantation Tolerance/drug effectsABSTRACT
The continued discovery of novel immune molecules and pathways over the last decade has spurred a tremendous amount of research into the targeting of these pathways for the prevention of transplant rejection. Of particular interest are members of the ever-growing family of T-cell co-stimulatory pathways; the classic co-stimulatory pathways are the CD28/CTLA4:B7-1/2 and CD40:CD154, while the ICOS:ICOSL and PD-1:PD-L1/PD-L2 pathways are novel. Various chimeric molecules and monoclonal antibodies have been developed for targeting these pathways with promising results, especially with the newer generation of agents and in combination among themselves, with other immunomodulatory therapies and/or with conventional immunosuppressive agents. These novel immunomodulatory strategies have the potential to bring us a step closer to achieving transplantation tolerance.