For thousands of patients, stem cell transplantation (SCT) is a potentially life-saving treatment as it is a procedure that replaces defective or damaged cells. Stem cells can develop into different healthy cells within the body. Therefore, it is a widely accepted treatment for many life-threatening diseases.
Stem Cells Possibilities
A stem cell can become any one of the 220 different cells in the body
Today an increased number of stem cell transplantations (SCT) are being performed thanks to the hematopoietic stem cells (HSC) from volunteer donors. Here is an overview of Hematopoietic stem cells!
- Stem cell transplantations (SCTs) require the replacement of hematopoietic stem cells (HSCs) obtained from the patient (autologous SCT) or HLA-matched donor (allogeneic SCT). In cases of donor stem cell transplant, the match should be > 90%.
- HSCs are the unique, multipotent, self-renewing cells that can produce different cells in the body. These can be found in bone marrow, peripheral blood, and umbilical cord blood.
- HSC is used to treat immune system diseases and blood disorders including leukemia, lymphoma, myeloma etc.
Hematopoietic stem cell transplant
What is HLA?
Human leukocyte antigens are the protein molecules we inherit from our parents that are found on the surface of the blood and in the tissue cells. The key role of the HLA complex is to regulate the immune system by differentiating the body’s own proteins from the foreign ones; such as viruses, cancer cells, bacteria and others.
Therefore, to find out whether you can be a donor, you will need an HLA or human leukocyte antigen test as it is important in SCT to determine how closely the HLA of the patient matches the HLA of the donor. This will give the recipient’s body the best possible chance to accept the foreign cells.
Currently, scientists have discovered nearly 600 different HLA molecules and HLA types are not evenly distributed among the population. It can vary due to different ethnicities. Therefore, some HLAs are more frequently found than others.
What Makes a Close Match? Overview of HLA Typing
The HLA typing (match) is based on the number of common HLA molecules found between two people. The more molecules the recipient and the donor share, the perfect is the match. Furthermore, the greater the match, the donated stem cells less likely to be rejected by the body’s immune system.
- Principally, the ideal SCT donor is a close relative, such as siblings considering they share the same parents.
- We have many HLA markers. Both the biological father and mother carry two sets of HLA, and each set is known as a haplotype. And HLA is inherited 50% from the father and 50% from the mother.
- If two siblings inherit the exact same HLA molecules from both parents, they are known as “HLA identical match”.
- According to the HLA inheritance rule (between parents and children), you have a 25 percent chance of being an HLA identical match with your sibling by inheriting identical HLA molecules (i.e. two haplotypes) as your sibling. On the other hand, you have a 25 percent chance of not inheriting the same HLA molecules as your sibling and a 50 percent chance of sharing one haplotype with your siblings.
- In case, no close HLA match is found within the family, the doctors will search for an unrelated donor with the same HLA molecules as the patient.