Tissue Typing Laboratory

29.08.2024


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TISSUE TYPING LABORATORY

Disease-associated tissue typing, determination of tissue type compatibility of donor and recipient at low-resolution and/or high-resolution for solid organ transplantation (kidney, lung etc.) before bone marrow transplant, tissue type compatibility of donor/recipient candidates at low-resolution and/or high-resolution, Panel Reactive Antibody Screening, identification and determination of anti-HLA antibodies produced against foreign HLA antigens by performing single antigen tests and determination of HLA antibodies produced in recipient against donor by performing analysis of Lymphocyte Crossmatch Tests in cadaveric and potential live-donor transplants before and after transplantation in our lab.

Our laboratory offers service between the hours of 08.00/17.00 during weekdays but in case of solid cadaveric organ transplant, our service continues 7/24 uninterruptedly during off-hours and holidays by the laboratory supervisor/deputy laboratory supervisor and the other lab staff on stand-by duty. Cutting-edge technology is utilised to obtain reliable and rapid results. We work based on the test kits conforming to the international standards. Maintenance & repair and calibration of all the equipment in our lab are carried out elaborately and recorded in time by either the authorized firms or lab workers.    

 

TISSUE TYPING TESTS 

The main objective of our body's defense system is to protect our body from foreign organisms such as bacteria, virus, cancer cells which are not a part of it. Identification of foreigner antigens and building a defense mechanism against those by our immune system is a must to survive. Despite this mechanism usually provides benefit to be protected from various microorganisms, it may not be possible to speak of any benefit when organ or tissue transplant from another individual is performed or when it generates reaction against self-antigens of the individual.

The gene region coding ''Tissue antigens'' that are necessary for our immune system to recognize which is self and which is not is defined as Major Histocompatibility Complex (MHC) The gene region coding Human Leukocyte Antigen HLA is located on chromosome 6 in humans. Human Leukocyte Antigen forms an individual's tissue type. MHC proteins recognizes foreign proteins which attaches to our cells, thus defense mechanism cells in our body attack those foreign proteins. There are numerous HLA Antigen Pairs in human body (the most well known ones are A, B, C, DRB1, DQB1 and DPB1) One sample from each of those antigen pairs of the mother and the father is taken and one from each pair is inherited to the child. Thus, there is a %25 chance of matching for all the sisters and brothers having the same mother and the father. However, sisters and brothers to be the first priority, mother, father and other close relatives must undergo HLA matching test not to miss any potential donor out.


How does the analysis process of tissue typing test work?

 

HLA Typing must be performed by trained and experienced staff. DNA sample derived from any cellular nuclei is used for studies. Leukocytes in peripheral blood are typically preferred. HLA typing is performed at low-resolution and/or high-resolution by molecular methods. Results are analyzed by laboratory test and analysis supervisor and laboratory supervisor/deputy laboratory supervisor to determine HLA matching donors   afterwards. A close match between recipient and donor candidate enhances the chance of a successful transplantation, contributing to engraftment, reducing the potential risks of graft-versus-host disease.     

 

Panel Reactive Antibody (PRA)

Anti-donor antibodies in kidney transplantations is one of the key parameters for graft survival. The risk of occurence of hyperacute rejection in transplants in the presence of produced antibodies of the patient against HLA antigens of the potential donor is quite a few. These antibodies are produced caused by rejected transplantations, pregnancy and blood transfusions and generally it is defined as Panel Reactive Antibody (PRA)

 

The reasons of the production of panel reactive antibodies;

Blood Transfusion:

Blood transfusions is one of the greatest risks for anti-HLA antibody production. There is a risk of antibody production after 5 units of whole blood transfusion approx. Some cases were seen which antibody production occured after one unit of blood transfusion.

Pregnancy: Anti-HLA antibody is produced in a ratio of approximately 1/8 especially in women having multiple pregnancy including miscarriage, curettage. HLA Antibody is not produced in every pregnancy. Normally, placenta doesn't allow the transfer of HLA antigens from the father to the mother. However, when bleeding occurs in placenta-related anomalies, paternal antigens may enter the maternal bloodstream and antibodies in the mother may be produced. The reason of antibody production is HLA antigens inherited from father to son.

 

Tissue or Organ Transplants

Antibodies start to increase instantly in rejections after organ transplants. Thus, anti-HLA antibody tests must be performed periodically in patients with suspected rejection during the post transplant stages. 

 

How does the analysis process of panel reactive antibody test work?

Panel Reactive Antibody Test must be performed by trained and experienced staff. A blood sample is collected from your arm by a standard method.  A plasma of the patient is derived from the taken blood sample and PRA test is performed by the laboratory staff. The results are analyzed by laboratory test and analysis supervisor, laboratory supervisor/deputy laboratory supervisor to determine whether panel reactive antibodies are produced or not and if the answer is yes to determine against which antigens they are produced.

 

Lymphocyte Crossmatch Tests (LCM)

Plasma and cells of the recipient and donor are mixed after choosing the donor in order to test immune responses caused by minor incompatibilities between recipient and donor despite full match in patients whose panel reactive antibody is negative and patients having a tissue compatible donor. Thus, the possibility of HLA antibody level to be produced in the recipient against the donor is determined.

How does the analysis process of lymphocyte crossmatch test work?

Lymphocyte Crossmatch Tests must be performed by trained and experienced staff. Blood samples are collected from the arms of recipient and donor/donors in different tubes by the standard method. Plasma of the recipient is derived from the blood sample taken. T and B Lymphocyte cells isolated from the other tubes for the recipient and the donor. The plasma of the recipient and T and B lymphocytes of the donor are subjected to cross reactivity to perform crossmatch testing. Results are analyzed by laboratory test and analysis supervisor, laboratory supervisor/deputy laboratory 

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