Nikhil (name changed), a 10 year old boy was diagnosed with Beta Thalassemia Major – a severe form of blood disorder. As the days passed by, his health started deteriorating at a fast pace. However, according to the doctors there was a ray of hope – Neeraj, his 7 year old brother. His umbilical cord blood was harvested and saved after his birth and that meant Nikhil’s chance of survival. Presently, cell-stem transplant is the only cure for B-Thal major.
To match the compatibility of the donor and the receiver, HLA Typing is necessary. After the typing, the compatibility was matched. After a successful transplant, Nikhil made a recovery and now shows no signs of B-Thal.
HLA (human leukocyte antigen) is a protein or marker – found on cells in human body. Immune system uses HLA markers to know which cells belong in our body & which don’t. Its main use is in organ and tissue transplant treatments. It checks if receiver and donor are compatible.
For example, in bone marrow transplant, HLA genes and antigens of donor and the recipient should be same or match closely for a transplant to be successful. Otherwise the donor’s tissue may get attacked or rejected by the recipient’s immune system.
What is HLA Typing?
A high-resolution typing result is defined as a set of alleles that encode the same protein sequence for the region of the HLA molecule called the antigen binding site and that exclude alleles that are not expressed as cell-surface proteins.
Every person (except identical twins) has different sets of HLA alleles. Transplanted organs are allografts, in which the donor organ and the recipient are genetically different. Compatibility (matching) of the HLA of the donor and the recipient increases the chance for a successful engraftment. Matching is determined by comparing alleles. Resolution is the level of detail with which an allele is determined. The MHC is a polymorphic locus encoding the HLA genes.
Antigens encoded by the HLA genes are responsible for allograft tissue and organ rejection. Identifying and matching alleles increases the chance of successful organ and tissue transplant. These antigens help the body’s immune system distinguish which cells are “self” and which are “foreign” or “non-self.” Any cells that are recognized as “non-self” can trigger an immune response, including the production of antibodies.
Different kinds of transplants necessitate different levels of matching between donor and intended recipient. This may determine which HLA tests are performed and which HLA genes are tested for.
HLA antigens and their corresponding sequence alleles are determined by serological- and DNA- based methods.
Why is it necessary?
Determination of HLA alleles by DNA typing techniques is necessary for HLA matching of donor and recipient at transplantation, medical research of HLA-related diseases and individual identification including paternity testing.
This testing also includes screening transplant recipients for the presence of antibodies that might target the donated tissue or organ as part of an immune response.
HLA mismatches found using very sensitive tissue-typing methods — methods known as “high-resolution” typing — can have just as significant an impact on transplant outcomes as mismatches found using “low-resolution” methods.
High-resolution typing is important for ensuring the best possible match between donor and recipient because a match suggested by Low Resolution HLA Typing is generally only 56% accurate.