Transplant

Question 1

Explain direct allorecognition. What kind of rejection?

Answer 1

Recipient T cells recognise donor MHC from donor APC.

Direct cytotoxic T cell response –> ACUTE REJECTION

Donor APC
Donor MHC: recipient peptide
Recipient T cell

Question 2

Explain indirect allorecognition. What kind of rejection?

Answer 2

Recipient APC processes peptides from inflammed/dead cels from donor organ.

Recipient T cell migrates to graft and attacks it –> tissue injury –> CHRONIC REJECTION

Recipient APC
Recipient MHC: donor peptide
Recipient T cell

Question 3

Describe hyperacute rejection

Answer 3

Recipient carries pre-existing antibodies (from previous transfusion/transplant)

Pre-existing antibodies react with Ag on vascular endothelium of transplanted organ

Question 4

What cells are involved in acute rejection. Timeline for rejection.

Answer 4

T cell mediated.
Graft rejected after 2 weeks.
2nd graft from same donor rejected within 6-8 days (hyperacute rejection from first graft)

Question 5

What happens to the organ during chronic rejection

Answer 5

• arteriosclerosis of graft blood vessels
• ischaemia reperfusion injury
• chronic inflammation and scarring

Question 6

Describe graft versus host disease

Answer 6

Donor cells see recipient as foreign, try to reject recipient.

• Only happens if donor graft contains immunologically competent cells (so won’t happen if T cells not present)
• Host must possess antigens that are lacking in donor graft so host appears foreign
• Host must be incapable of mounting effective immunologic reaction against graft

Question 7

What occurs during corneal transplant? Any matching critical?

Answer 7

Immune privileged site so no lymphocytes.

No rejection

Question 8

What occurs during solid organ transplant? Any matching critical?

Answer 8

Blood group matching critical.

HLA matching ideal but not critical.

Long term immunosuppression needed.

Question 9

What occurs during bone marrow transplant? Any matching critical?

Answer 9

HLA matching critical. (New T cells must recognise HLA on thymic epithelium to train T cells to recognise MHC:antigen)

Blood group matching ideal but not critical.

Long term immunosuppression not needed.

Question 10

In which patient group might blood group matching not be critical? Why?

Answer 10

Infants.

Rejection involves polysaccharide response and young infants don’t make polysaccharide antibodies so don’t have anti A and anti B