tissue typing mrs. stewart medical interventions central magnet school © 2010 project lead the way,...

Tissue Typing

Mrs. Stewart

Medical Interventions

Central Magnet School

© 2010 Project Lead The Way, Inc.Medical Interventions

Essential Questions

1. How are organ donors and recipient matched?

2. What % compatibility is acceptable between a donor and a recipient?

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 + + +

Human Leukocyte Antigens (HLA)

• A group of antigens located on the surface of a person’s leukocytes

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).

Think – Pair – Share

• Why is HLA typing necessary when matching up a kidney donor and recipient?

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

• 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.

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)

• 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

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

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.

% 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.

Conclusion Question # 2

• Why is there a 25% chance of a six-antigen match between siblings?

Which HLA will we test for?

• Kidney transplants look at the following HLA antigens:– HLA-A – HLA-B– HLA-DR

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).

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?

Conclusion Question # 3

• Based on blood typing and HLA typing results, who is the most suitable match for Diana? Explain your answer.

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.

Think – Pair – Share

• How can marker analysis determine which HLA alleles are present? Hint: Refer back to Activity 3.2.3.

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.

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.

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.

Think – Pair – Share

• How is a cross-matching test similar to a blood typing test?

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?