Tissue typing
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Tissue Typing. Everyone has several antigens located on the surface of his/her leukocytes:. One particular group of these antigens is called the HLA (Human Leukocyte Antigens). The HLA. Is responsible for stimulating the immune response to recognize tissue as self versus non-self.

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Tissue Typing

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Tissue typing

Tissue Typing


Everyone has several antigens located on the surface of his her leukocytes

Everyone has several antigens located on the surface of his/her leukocytes:

  • One particular group of these antigens is called the HLA (Human Leukocyte Antigens).


The hla

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).


Tissue typing

  • The test that determines which HLA antigens are present is called tissue typing or HLA typing.

    • Tissue typing identifies the similarity of the antigens present in both the donor and the recipient.


Tissue typing

  • 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

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)


Tissue typing

  • 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


Tissue typing

  • The set of HLA antigens received from a parent is called a haplotype.

    • There are a variety of alleles for each of these HLA antigens.


Tissue typing

  • 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.


Tissue typing

  • When performing an HLA typing test for a kidney transplant, the following HLA antigens are looked at:

    • HLA-A

    • HLA-B

    • HLA-DR


Tissue typing

  • 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).


Tissue typing

  • Six HLA antigens are looked at for each person.

    • Remember each person has two of each of the antigens (one inherited from the mother and one inherited from the father).


Tissue typing

  • By analyzing which six of these HLA-antigens both the donor and recipient have, scientists are able to determine the closeness of tissue matching.

    • 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.


Hla typing techniques

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.


Tissue typing

  • Once the donor and recipient have been tested for tissue compatibility, the next step is an Antibody Screening (also calleda Panel Reactive Antibody or PRA).

    • A small amount of the organ recipient’s serum is mixed with cells from 60 different individuals (each test is done separately).


Purpose of antibody screening

Purpose of Antibody Screening

  • Scientists can determine how many different HLA antibodies a patient has in his/her blood.

    • 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

Crossmatch Test

  • After tissue typing and antibody screening are complete and a potential donor has been identified, the final test is called a crossmatch test.

    • 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.


Tissue typing

  • 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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