Introduction to the Immunology of Transplants and Tumors Flashcards
(22 cards)
What is a syngeneic graft?
A genetically identical graft so it is easily accepted; rare only in identical twins
What is an allogeneic graft?
Same species with genetic differences; they are rejected by the immune system at different extents
What is a xenograph?
Different species organ graft
What are the three mechanisms of rejection?
Hyperacute; acute; chronic
What is an alloantigen?
Primary target of rejection: MHC (HLA) proteins class I and class II
What are xenoantigens?
Targets of rejection in a xenograph typically endothelial cell antigens and blood cell antigens
What is the timing for a hyperacute rejection?
Within minutes of transplantation
What is the culprit in hyperacute rejection?
Pre-existing circulating antibodies specific for graft antigens
What is the clinical significance in hyperacute rejection?
The major barrier in xenotransplantation; not a big issue in donor/recipient testing
What is the timing for a acute rejection?
Within days or weeks of transplantation
What is the culprit in acute rejections?
Immune response against graft alloantigens (CD8+ CTLs, CD4+ T cells)
What is the clinical significance of acute rejection?
Causes major organ rejection but can be prevented/curbed by immunosuppressive therapy
What is the timing for chronic rejection?
Occurs over months or years after transplant
What is the culprit in chronic rejections?
Immune response against graft alloantigens, chronic inflammatory reaction (CD4+ T cells)
What is the clinical significance of chronic rejection?
Causes major problem; not affected by immunosuppressive therapy
What is immune surveillance?
The idea that the immune system can control and eliminate malignant cells
What is a tumor antigen?
An antigen expressed only on malignant cells not on normal cells; may be recognized by immune system as a foreign antigen
What is the primary mechanism of immune mediated tumor rejection?
Dendritic cell engulf and presents antigen to CD8+ CTLs specific for tumor antigen there is then a normal immune response against the antigen
What are three anti-tumor immunotherapy strategies?
Passive immunity
2 Types of active immunity
How is passive immunity used in anti-tumor therapy?
Tumor-antigen specific T cells removed from patient and expanded in vitro and transferred back; Monoclonal antibodies specific for tumor antigen transferred to the patient
How are vaccines used against tumors?
Dendritic cells are loaded with tumor antigens and then injected into the patient, the dendritic cells present to tumor specific T cells activating them against tumor cells
How are monoclonal antibodies used against tumors?
Monoclonal antibodies specific for inhibitory receptors on T cells are injected (CTLA-4 and PD-1) The antibodies then bind the inhibitory sites activating tumor-specific T cells that attack the tumor
