Title: Transplant surgery
15 March 2016
Learning question: What are the pros and cons of transplant
surgery?
Homework: Read and make notes on spreads from pp206-209.
Answer textbook questions and complete last paper questions. Mark
all questions using the mark schemes provided.
Face transplant patient
http://www.bbc.co.uk/news/w
orld-us-canada-17534646
BBC documentary on the first
recipient of a face transplant
Learning Objectives
(a) explain the significance of genetic compatibility in
transplant surgery with reference to the major
histocompatibility (MHC) system
(b) State the potential sources of donated organs and
outline the advantages and disadvantages of each
source
(c) Outline the potential of genetic engineering in the
use of non-human organs for transplant surgery
Genetic compatibility
Genetic compatibility
• Tissue transplanted from one person into another will bring
about an immune response to the foreign tissue and be
destroyed – this is called tissue rejection.
• This will always occur between to individuals, even from
the same family, unless they are identical twins.
• The ability to accept a transplanted organs, without tissue
rejection is called compatibility.
• This includes looking at the degree of genetic similarity at a
particular locus of two individuals
Genetic compatibility
• Initially, a blood test is carried out to see if
the patient and the recipient’s blood types
match
• Tissue typing is next: with the exception of
RBCs, all cells carry antigens other than A
and B in their cell surface membranes.
• The human leucocyte antigen system
(HLA) is of particular interest.
• HLA genes are found on chromosome 6.
• 6 gene loci are involved, known as the
Major Histocompatibility Complex (MHC)
Genetic compatibility
• HLA genes are so close together, they are linked
(transmitted into the same gamete together)
• Each set of HLA antigens from chromosome 6 is
referred to as a haplotype. We get 2 copies –
one from each parent.
• The loci of these antigens are given letters to
identify them.
• Each of the six loci has a large number of alleles.
• This means that you could have an HLA-A1, B8,
DR17!
Questions
1. How many haplotypes will you have in each liver cell?
2. What does the term compatibility mean in the field of
transplant surgery?
3. What does MHC stand for?
4. What chromosome would you find MHC?
5. What do the genes in the MHC region code for?
Answers
1. 2
2. Compatibility is the ability to accept
transplanted tissue.
3. Major histocompatibility complex
4. Chromosome 6
5. HLA antigens
Genetic compatibility
• More precise tissue matching is being carried
out with the advent of DNA technology.
• Polymerase chain reaction (PCR) is replacing
traditional serological techniques
• More accurate and specific HLA typing, which
means more precise HLA matching between
donors and transplant patients.
Sources of donated organs
• Cadavers used to be a good source of organ
harvesting, but with a lower mortality rate, other
options are being explored.
• Why are more people surviving?
• Road safety
• Medical advances
• Prevention of strokes
Sources of donated organs – extended
criteria
• Older donors being considered (e.g. livers over 70 years
old)
• Unsuitable hearts being used as a “bridge” until a suitable
one is found
• Livers can be split into two for two patients
• One kidney may be donated by a living relative
• “Domino” transplants – patients needs a new set of lungs,
but gets a new heart and lungs because this operation is
easier to perform. The patient’s heart is then given to
someone else who needs the healthy heart
Success of donated organs
• Living donors have a better outcome than
cadavers (95% to 86% success rate respectively
for kidney donation)
• Ideal donor is an identical twin, then a sibling.
Failing that, a blood relative are more likely to
match than a stranger
• Living donors can donate bone marrow, liver
lobes, lung lobes and kidneys
Ethics of organ donation - Is it wrong to
sell organs?
Ethics of organ donation - Is it wrong
to sell organs?
• Senior NHS doctors have complained about
botched transplant surgeries done abroad
• Doctors in India see poor donors dying after
selling one of their kidneys
• In March 2007, China published new rules
governing human organ transplants – buying and
selling organs is forbidden. Written permission
from doctors is required before operation is
carried out
Xenotransplantation
• Animal – human transplantations are being studied by some
transplant centres.
• Pigs may be a possible source of transplant organs….what do
you think?
• What are the implications of this?
Question
1. Name four different sources of donated
organs for transplant surgery. Which would
be likely to have the best outcome? State
one problem associated with each source.
Answer
• Cadavers – establishing brain death,
permission
• Living donors – need a good tissue match
• Xenotransplantation – immunological
rejection, transfer of disease, sale of organs,
monetary pressure, poorly executed
operations to remove the wanted organ