Medical Interventions Tissue Typing Mrs. Stewart Medical Interventions Central Magnet School Medical Interventions © 2010 Project Lead The Way, Inc.

Essential Questions How are organ donors and recipient matched? 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. Children inherit one haplotype from each parent. Therefore, there are a total of four different haplotype combinations from two parents.  Because of this, there is a basic rule in HLA inheritance. The rule is: you have a 25% chance of inheriting all of the same HLA (same 2 haplotypes) as any one of your siblings, you have a 25% chance of not inheriting any of the same HLA (none of the same haplotypes) and you have a 50% chance of sharing I haplotype with your siblings. Therefore, you have a 25% (1 in 4) chance of being an identical match with your siblings.

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).

Who has an HLA match? HLA-A, HLA-B, and HLA-DR Antigens Diana Jones HLA-A2, HLA-A10 HLA-B7, HLA-B16 HLA-DR11, HLA-DR8 Jennifer HLA-A 1, HLA-A 10 HLA-B 3, HLA-B 16 HLA-DR 8, HLA-DR 35 Jack HLA-A 1, HLA-A 6 HLA-B 3, HLA-B 9 HLA-DR 35, HLA-DR 4 Louis HLA-A 10, HLA-A 2 HLA-B 7, HLA-B 16 HLA-DR 8, HLA-DR 11 Judy Smith HLA-A 6, HLA-A 2 HLA-B 7, HLA-B 9 HLA-DR 11, HLA-DR 4 Sue Smith HLA-A 2, HLA-A 40 HLA-B 7, HLA-B 6 HLA-DR 11, HLA-DR 5 Emily Jones HLA-B 8, HLA-B 16 HLA-DR 20, HLA-DR 8 Sarah Jones HLA-A 1, HLA-A 2 HLA-B 8, HLA-B 7 HLA-DR 11, HLA-DR 20 Jordan Jones HLA-A 3, HLA-A 10 HLA-B 16, HLA-B 14 HLA-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?