Matchmaking-Donors in Stem Cell Transplants

by Dr. Madhav Danthala | Apr 08, 2022 | Hematology & BMT | 4236 22

1. What is a Bone Marrow Transplant?

2. Types of Transplant

3. What is HLA typing (Human Leukocyte Antigens)?

4. What are the origins of HLA antigens?

5. Is the HLA antigen divided?

6. How is HLA matching done?

7. How to search for a suitable match?

A bone marrow transplant is a medical procedure that replaces bone marrow with healthy replacement cells that can be taken either from a patient’s body or from a donor.

Why are most people reluctant to join the bone marrow registry? Because some people believe that the only way to donate blood stem cells is through surgery. While in reality, more than 80% of the donations are peripheral blood stem cells and do not involve surgery at all.

Peripheral blood stem cells is a noninvasive surgery where the donor will be given filgrastim injections for 5 days to enhance the quantity of cells in the bloodstream that will be used for transplantation. A needle in one arm is used to extract some of your blood, which is then run through a machine that separates the blood-forming cells. The blood that is left is returned to you via the opposite arm.

Bone marrow donation is a surgical treatment that is frequently performed on an outpatient basis. The process starts with injecting a dose of the anesthetic and then extracting liquid marrow from the back of your pelvic bone using two small punctures with a needle.

What is a Bone Marrow Transplant?

A bone marrow transplant is a medical procedure that replaces bone marrow with healthy replacement cells that can be taken either from a patient’s body or from a donor. Bone marrow transplants or stem cell transplants (more specifically, a hematopoietic stem cell transplant) help to save the lives of people with blood cancers such as leukaemia, myeloma, lymphoma, and other blood or immune system diseases.

Types of Transplant

There are 2 types of bone marrow/stem cell transplants:

Autologous transplant: An autologous transplant involves extracting stem cells from the patient’s blood or bone marrow. This form of treatment is more effective than the intensive chemotherapy or radiation therapy that affects the stem cells and immune system. After the chemotherapy, the cells are then returned to your body, bringing back the immune system to make blood cells and fight infection.

Allogenic transplant: In an allogeneic transplant, the stem cells are extracted from a donor and then given to the patient once the chemotherapy or radiation therapy is done. The crucial step during ALLO transplant is to find a healthy donor whose blood proteins, also known as human leukocyte antigens (HLA) , are genetically identical to the patients. This process is known as HLA typing. Patients are very unlikely to have serious side effects called graft-versus-host disease (GVHD), if the donor’s proteins are a good match.

What is HLA typing (Human Leukocyte Antigens)?

While blood can be given to millions of people with the same blood type, stem cell donors and recipients are meticulously matched one-to-one.

Human Leukocyte Antigens (HLAs), which coat the surfaces of peripheral blood stem cells and most other cells, are the key to discovering a favorable match. These “markers” aid in the differentiation of cells from viruses, bacteria, and cancer.

Since HLA antigens (tissue types) are passed from one generation to the next, a match for stem cell donation is more likely to be found within a family group. Mostly, siblings from the same parents make the best matches.

Human Leukocyte Antigens

What are the origins of HLA antigens?

HLA antigens are proteins that can be found in almost every cell in your body. These antigens are inherited as a unique set by your parents, which allows your immune system to be regulated. HLA genes are situated on chromosome 6’s short arm, and each person inherits two sets of antigens: one from each parent.

Is the HLA antigen divided?

Class I and class II HLA antigen groups are the two most common types. Everyone has a unique set of HLA markers, and to be matched, the majority of the donor’s markers must match the recipient’s. However, because there are so many different combinations of these markers, not everyone will find a match. Depending on the rarity of the individual’s HLA antigens, the chances of a donor matching the patient range from 1 in 450 to 1 in 750,000. The greater the match, the more HLAs the donor and recipient share. In the case of graft versus host disease (GvHD), the HLA system is crucial.

How is HLA matching done?

HLA matching is primarily done to match patients and donors for blood or marrow transplants. A match is defined by the similarity of HLA type among two people.

The receiver and potential donors will have blood drawn or have the inside of their cheek swabbed.

The HLA type is determined by testing blood or a cheek swab at a lab.

To see if there is a match, the HLA type will be compared to potential donors.

How to search for a suitable match?

Start with the siblings (matched sibling donor)

The patient’s siblings are initially screened for donors, with a 1 in 4 (25 percent) chance of being a match. However, the brother or sister may be too elderly, in poor health, or simply refuse to be a donor.

Unrelated donors matched

Patients in need of a life-saving stem cell transplant can use stem cell registries to find donors. They compile databases of potential donors that doctors can review when their patient needs a stem cell transplant to make the pairing easier. Every new registration brings hope to those who have been waiting.

Alternative donors

Mismatched unrelated donors (not a perfect match but still good enough to be a donor).

Transplantation of cord blood (source of stem cells is the umbilical cord blood of healthy newborns). Haploidentical donors are also called half-match, transplants with a biological parent, child, or sibling.

Donate to help the needy!

Thousands of people are diagnosed every year with life-threatening diseases like leukaemia or lymphoma for which stem transplants are considered the life-saving treatment. This treatment requires donated blood stem cells.

If you find that your family member, friend, or a needy stranger is searching for a blood stem cell donor, then take a step forward to donate and save a life. For those who need transplants, HLA typing is a crucial step. They have the highest chance of a successful transplant if they can find a good match.