Transplant Immunology

Question 1

Autograft

Answer 1

Graft from one area to another on same individual

Question 2

Isograft (syngraft)

Answer 2

Graft from one individual to another who is
genetically identical (syngeneic) to the donor

Question 3

Allograft

Answer 3

Graft between unrelated or allogeneic individuals

Question 4

Xenograft

Answer 4

Graft between a donor and recipient from different species

Question 5

Hyperacute Rejection

Answer 5

• Occurs within a few minutes to a few hours of transplant (fever,
tenderness and pain)
• Pre-existing antibodies to ABO, MHC, or endothelial antigens
• Antibodies bind vascular endothelium & activate complement
• Platelet deposition &; thrombi in capillaries;vascular congestion
• Transplanted organ must be removed
graft becomes enlarged and purple due to hemorrhage

Question 6

Acute Rejection

Answer 6

• Mainly T cell mediated damage of graft
• Fever and graft tenderness, edema
• Occurs a few days to a few weeks after transplantation
• Interstitial infiltrates of T lymphocytes and macrophages
• CD4 TH1 and CD8 T cells induce DTH response
• CTL (CD8 T cell) mediated killing of graft cells; (Direct recognition)
• CD4 T cells secrete cytokines that induce inflammation & vessel damage (vasculitis)
• Alloantibodies that bind to alloantigens (HLA molecules) on endothelial cells of graft can also cause endothelial injury and intravascular thrombosis
• Classical pathway of complement activated and complement mediated tissue injury ensues
• Can be reversed with immunosuppressive therapy

Question 7

Chronic Rejection

Answer 7

• Mediated by T cells and alloantibodies
• Occurs months or years after transplantation
• T cells react against graft alloantigens; mostly CD4
• secrete cytokines that cause inflammation and damage graft
• Cytokines stimulate fibroblasts resulting in FIBROSIS
• Inflammation of arteries causing OBSTRUCTION and fibrosis
(vascular occlusion); arteriosclerosis
• Mononuclear infiltrates in interstitium
• Alloantibodies contribute to vascular destruction by recruiting complement (classical pathway) and promoting inflammatory response
• Patients do not respond to therapy
• Graft usually has to be removed

Question 8

Graft Versus Host Reaction

Answer 8

• Consequence of transferring allogeneic bone marrow or stem cells to an immunocompromised host
• Initiated by residual mature donor T lymphocytes in the bone marrow
• Donor T cells recognize and react to MHC and minor H antigens on recipient’s dendritic cells unless they are removed
• Waisting syndrome
• Splenomegaly, hepatomegaly, lymphadenopathy, anemia, weight loss, chronic

Question 9

O Blood group (O-)

Answer 9

universal Donors

Agglutination assay used to test ABO blood group • Patient’s blood mixed with antiserum to A or B

Question 10

AB blood groupd (AB +)

Answer 10

universal recipients

Agglutination assay used to test ABO blood group • Patient’s blood mixed with antiserum to A or B

Question 11

Alloreactivity

Answer 11

Happens bc some T cells get through that can respond to allogenic (foreign) MHC and
basis for graft rejection..looks like SELF MHC plus foreign peptide because these stupid t cells recognize foriegn MHC

Question 12

Direct Graft recognition

Answer 12

in lymph nodes t cells get activated by donor APCs from the graft, that display alloreactive MHC and forigen peptide
activated t cells move to graft and destroy graft cells
DONOR APC presents peptide from graft to RECIEPIENT T CELLS

Question 13

Indirect Graft Recognition

Answer 13

Graft cells may be ingested by recipient dendritic cells + then donor alloantigens are presented by self MHC molecules on reciepeint APCs to CD4 cells
- may play a greater role in chronic rejection