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Transcript of Tissue Typing Mrs. Stewart Medical Interventions Central Magnet School © 2010 Project Lead The Way,...
![Page 1: Tissue Typing Mrs. Stewart Medical Interventions Central Magnet School © 2010 Project Lead The Way, Inc.Medical Interventions.](https://reader033.fdocuments.in/reader033/viewer/2022061510/56649d305503460f94a0817e/html5/thumbnails/1.jpg)
Tissue Typing
Mrs. Stewart
Medical Interventions
Central Magnet School
© 2010 Project Lead The Way, Inc.Medical Interventions
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Essential Questions
1. How are organ donors and recipient matched?
2. What % compatibility is acceptable between a donor and a recipient?
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Review – Conclusion Question # 1
• Based on blood type alone, who can donate a kidney to Diana? Blood Sample Agglutination with
Anti-A Serum (+/-)Agglutination with Anti-B Serum (+/-)
Agglutination with Anti-Rh Serum (+/-)
Blood Type
Diana Jones + - +
Jennifer + - +
Jack - + +
Louis + - +
Judy Smith - - +
Sue Smith - + +
Emily Jones + + +
Sarah Jones - - +
Jordan Jones + + +
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Human Leukocyte Antigens (HLA)
• A group of antigens located on the surface of a person’s leukocytes
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The HLA
• Is responsible for stimulating the immune response to recognize tissue as self versus non-self.
• Is controlled by a set of genes located next to each other on chromosome 6 called the Major Histocompatibility Complex (MHC).
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Think – Pair – Share
• Why is HLA typing necessary when matching up a kidney donor and recipient?
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HLA typing (tissue typing)
• The test that determines which HLA antigens are present–Tissue typing identifies the similarity
of the antigens present in both the donor and the recipient.
–More than just blood type matching
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• The closer the HLA antigens on the transplanted organ match the recipient, the more likely that the recipient’s body will not reject the transplant.
• For this reason, tissue typing of the kidney donor and recipient is necessary before a kidney transplantation.
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There are two main classes of HLA antigens:
• Class I (HLA-A, HLA-B, and HLA-Cw)
• Class II (HLA-DR, HLA-DQ, and HLA-DP)
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• Every person inherits each of the following antigens from each parent:– HLA-A antigen– HLA-B antigen– HLA-Cw antigen– HLA-DR antigen– HLA-DQ antigen and– HLA-DP antigen
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Haplotypes
• The set of HLA antigens received from a parent–There are a variety of alleles for
each of these HLA antigens.–The set of alleles inherited for any
trait is a haplotype
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Why are family members more likely to match?
• The large number of possible variations and combinations of HLA antigens make finding a match in a family more likely than finding a match in the general public.
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% match in families
• A six-antigen match is the best compatibility between a donor and recipient.
• This match occurs 25% of the time between siblings who have the same mother and father.– Children inherit one haplotype from each
parent. Therefore, there are a total of four different haplotype combinations from two parents.
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Conclusion Question # 2
• Why is there a 25% chance of a six-antigen match between siblings?
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Which HLA will we test for?
• Kidney transplants look at the following HLA antigens:– HLA-A – HLA-B– HLA-DR
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Numbering Alleles
• The MHC genes are the most polymorphic known.– There are hundreds of known alleles for each
HLA Antigen.• Each allele is identified by a number (i.e. HLA-A1
or HLA-A2).
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HLA-A, HLA-B, and HLA-DR AntigensDiana Jones HLA-A2, HLA-A10
HLA-B7, HLA-B16HLA-DR11, HLA-DR8
Jennifer HLA-A 1, HLA-A 10HLA-B 3, HLA-B 16HLA-DR 8, HLA-DR 35
Jack HLA-A 1, HLA-A 6HLA-B 3, HLA-B 9HLA-DR 35, HLA-DR 4
Louis HLA-A 10, HLA-A 2HLA-B 7, HLA-B 16HLA-DR 8, HLA-DR 11
Judy Smith HLA-A 6, HLA-A 2 HLA-B 7, HLA-B 9HLA-DR 11, HLA-DR 4
Sue Smith HLA-A 2, HLA-A 40HLA-B 7, HLA-B 6HLA-DR 11, HLA-DR 5
Emily Jones HLA-A 1, HLA-A 10HLA-B 8, HLA-B 16HLA-DR 20, HLA-DR 8
Sarah Jones HLA-A 1, HLA-A 2HLA-B 8, HLA-B 7HLA-DR 11, HLA-DR 20
Jordan Jones HLA-A 3, HLA-A 10HLA-B 16, HLA-B 14HLA-DR 8, HLA-DR 17
Who has an HLA match?
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Conclusion Question # 3
• Based on blood typing and HLA typing results, who is the most suitable match for Diana? Explain your answer.
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HLA Typing Techniques
• Traditionally, HLA typing was done using serological techniques:– Blood from the patient was mixed with serum
containing known antibodies to determine which antigens were present.
• HLA typing now is predominantly done using molecular techniques:– Patient’s DNA is isolated.– PCR is used to amplify specific HLA genes.– Genes are sequenced to determine which alleles are
present.
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Think – Pair – Share
• How can marker analysis determine which HLA alleles are present? Hint: Refer back to Activity 3.2.3.
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Antibody Screening / Panel Reactive Antibody (PRA)
• A small amount of the organ recipient’s serum is mixed with cells from 60 different individuals (each test is done separately).– If a patient reacts with 30/60 cells, he/she is
said to have 50 Percent Reactive Antibody (also known as PRA).
– The lower a person’s PRA, the less likely he/she is to reject a transplant.
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Crossmatch Test
• The final test for compatibility • Crossmatch Test: A small amount of the
potential donor’s white cells is mixed with a small amount of the recipient’s serum.– By exposing the donor’s HLA to the recipient’s
serum, scientists can determine if the recipient has antibodies to any of the donor’s HLA.
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Results of Crossmatch Test
• Positive Crossmatch: A reaction between the donor’s and recipient’s samples occurs.– Indicates that the recipient’s body will likely reject the
implanted kidney.– Indicates the transplant cannot be performed.
• Negative Crossmatch: No reaction between the donor’s and recipient’s samples occurs.– Indicates that the recipient’s body will most likely not
reject the implanted kidney.– Indicates the transplant can be performed.
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Think – Pair – Share
• How is a cross-matching test similar to a blood typing test?
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Conclusion Question # 4
• Now that you have determined a suitable match for Diana, what additional test needs to be completed before the transplantation? Why are these next steps so important?