IMUNOLOGI TRANSPLANTASI

IMUNOLOGI TRANSPLANTASIDr. Fairuz Quzwain, SpPA, M.KesBagian Patologi AnatomiProgram Studi Pendidikan DokterUniversitas JambiA Major barrier to transplantation is the process of rejection

Rejection the recepients immune system recognizes the graft as being foreign and attacks it

Skin, Kidneys, heart, lungs, liver, spleen, bone marrow and endocrine organs.MechanismsThe antigens responsible for such rejection in humans are those of the HLA system

Every individual will recognize some HLA molecules in another individual as foreign

Rejection is a complex process in which both cell-mediated immunity and circulating antibodies play a role

T cell-mediated ReactionCalled cellular rejection

Induced by 2 mechanism : 1. destruction of graft cells by CD8+ CTLs 2. delayed hypersensitivity by CD4+ helper

The recipients T cell recognize antigens in graft bay 2 pathways, called direct and indirect

The direct pathway is the major pathway in acute cellular rejection, whereas the indirect pathway is more important in chronic rejection.Antibody-mediated ReactionCalled humoral rejection

Hyperacute rejection occurs when preformed antidonor antibodies are present in the circulation of the recipient. - Kidney transplantation - Blood transfusions

When preformed antidonor antibodies are present, rejection occurs immediately after transplantation because the circulating antibodies react with and deposit rapidly on the vascular endothelium of the grafted organ

Complement fixation occurs, resulting in thrombosis of vessels in the graft and ischemic death of the graft.The initial target of these antibodies in rejection appears to be the graft vasculature vasculitis MorphologyOn the basis of the morphology and the underlying mechanism, rejection reactions are classified as : Hyperacute, Acute , and ChronicHyperacute : - Occurs within minutes or hours - Ig and Compl are deposited in the vessel wall ( endothelium) - ex. Kidney : cyanotic, mottled, flaccid, excretes mere few drops of bloody urineAcute : - Occurs within days in the untreated recipient or may appear suddenly months or even years later after immunosupression has been employed and terminated - Vasculitis, interstitial mononuclear cell infiltrateChronic : - in recent years, acute rejection has been significantly controlled by immunosupressive therapy, and chronic rejection has emerged as an important cause of graft failure.- Dominated by vascular changes, intstitial fibrosis and atrophy.- The vascular changes consist of dense, obliterative intimal fibrosis. Increasing Graft Survival Minimizing the HLA disparity between the donor and the recipient would be expected to improve graft survival. Immunosupressive therapy cyclosporine