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Histocompatibility and Immunogenetics

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The primary function of the Histocompatibility and Immunogenetics laboratory are, histocompatibility testing for clinical transplantation and transplantation immunology research. The laboratory performs histocompatibility testing for clinical transplantation and disease association studies. The laboratory is licensed by the Federal Government under CLIA '88, the New York Department of Health, the American Society for Histocompatibility and Immunogenetics and the American College of Pathologists. The laboratory performs testing for kidney and bone marrow transplants. The laboratory also provides HLA typing and crossmatch services for the Organ Procurement Agency(NYODN) in New York.

Histocompatibility Testing Vocabulary:

Histocompatibility is the state in which a donor and recipient share antigens so that a graft is accepted and remains functional.

Immunogenetics is the study of immunity to disease and the relationship to genetic make-up.

HLA antigens are proteins on the surface of the cells in the body.

HLA function is to help the immune system defend against invaders such as bacteria, viruses and parasites and to recognize as foreign the histocompatibility antigens of other people's cells and fight them, causing rejection of graft.

What is Tissue Typing:

Tissue Typing is the name given to the test which identifies an individual's HLA. This information is critical before a patient receives a donor organ

HLA Matching - Because HLA antigens can be recognized as foreign by another person's immune system, transplantation professionals try to match as many HLA antigens as possible between the donated organ and the recipient.

HLA Genes - A person's genes are the blueprints that tell cells how to organzie the amino acids to make proteins. The HLA genes are on chromosome number six. They are passed down from parent to child. Each person gets two copies of each gene, one copy from the father and one from the mother. A child will not match either parent exactly, but will be a half match. Because each parent has two copies of each gene, there are four possible combinations of genes that could be passed down to their children.

Crossmatch is the second test which will indicate if there is specific immune reactivity between donor and recipient. The crossmatch is performed by mixing a small amount of the patient's serum with a small amount of the potential donor's white cells. If the patient has antibody to the donor's HLA, the donor's cells will be injured and this is referred to as a positive crossmatch. A patient can develop antibody after pregnancy, a transfussion, or a transplant. A positive crossmatch is a contraindication to transplantation

Antibody Screening and PRA - PRA(Panel Reactive Antibody) is the amount of HLA antibody in a patient's serum. If for example the patient's serum reacts with 30 out of 60 HLA, then the patient's PRA is 50%. The PRA is calculated for each monthly serum sample. In addition to determining how much or how little PRA a patient has, we need to know how specific the antibody is. Some patients have one of two antibody specificities, while others have numerous specificities. Since HLA antibody can "come and go" it is important to test the PRA regularly on a monthly basis.