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Allogeneic Stem Cell (Bone Marrow) Transplant

bone marrow medical illustration showing bone marrow, blood stem cells, platelets, red blood cells, and white blood cells

An allogeneic stem cell transplant uses a donor's healthy blood-forming cells. These cells are also known as hematopoietic stem cells. Stem cells are made in the spongy part of bones, called bone marrow. They make all types of blood cells in the body.

What is an allogeneic transplant?

An allogeneic transplant replaces damaged or destroyed blood-forming cells (stem cells) with healthy ones from another person. This person is called a donor.

The donor stem cells travel to your child's bone marrow. They grow and make healthy blood cells, including , , and .

Learn about transplants using the patient’s own cells: autologous stem cell transplant.

Diseases allogeneic transplants treat

Allogeneic transplants are used for certain cancers and blood disorders such as: 

  • High-risk leukemia or lymphoma 
  • Immune system diseases 
  • Sickle cell disease 
  • Thalassemia 
  • Bone marrow failure syndromes 
  • Metabolic storage disorders 
  • Some high-risk solid tumors 

 Steps of an allogeneic transplant 

The allogeneic transplant process involves:

  • Finding a donor
  • Pre-transplant testing and evaluation
  • Conditioning or preparative regimen using chemotherapy, antibodies, or radiation
  • Infusion of the donor's stem cells
  • Engraftment
  • Supportive care to manage side effects

  1. Finding a donor

    The first step in allogeneic transplant is to find a person to donate healthy stem cells. The transplant team will coordinate the donor search to find a matched donor. The donor can be a relative or unrelated to the patient.

    Donor matching means finding a donor whose cells have similar genetic markers. This is known as an HLA match. HLA stands for human leukocyte antigen.

    These markers are on the surface of most cells and play an important part in the immune system. If the donor cells are not well-matched to your child's HLA, your child's cells and the donor cells may attack each other.

    Doctors will also consider the donor's health and medical history.

    • Since genetic markers are inherited from parents, a biological brother or sister is the most likely the best match.
    • If no relatives are a good match, the cells may come from a volunteer donor who is well matched. Unrelated donors are found through the Be the Match Registry of the National Marrow Donor Program. 
    • If a good match can't be found, the doctor may suggest using a mismatched donor, which is a donor who is a close, but not exact, HLA match. In some cases, it is possible to use cells from a parent or family member who is a "half-match." This type of transplant is called a haploidentical (half-matched) transplant. Mismatched donor transplants are fairly common, and many are successful.

    After the donor is found, the stem cells will be collected from the donor and processed for the transplant.

  2. Pre-transplant testing and evaluation

    Your child will have an evaluation before transplant. The transplant process and recovery are physically and emotionally challenging. The medical team will do tests to make sure your child is good candidate for transplant.

    Your care team will consider factors such as:

    • Age of your child
    • Medical history and health of your child's heart, lungs, and other organs
    • Diagnosis
    • Prior treatment history
    • Availability of a donor

    Pre-transplant tests may include a complete medical exam, blood tests, and imaging studies such as CT, MRI, or X-rays.

    Your child will also have a central line for chemotherapy and medications during the transplant process.

    Other care team members may include child life specialists, social workers, psychologists, and palliative care specialists.

  3. Conditioning or preparative regimen

    To prepare for transplant, your child will go through a process called conditioning, or the preparative regimen. The conditioning treatment increases the chance that the transplant will be successful.

    Conditioning may include:

    • High-dose chemotherapy
    • Radiation therapy such as total lymphatic irradiation (TLI) or total body irradiation (TBI).
    • Antibody therapy to weaken the patient's immune system and reduce the risk of graft versus host disease (GVHD).

    The goal of conditioning is to:

    • Make room for new donor cells to grow
    • Weaken the immune system to make the body more accepting of the new donor cells. 
    • Kill any cancer cells left in the body 

    Conditioning will take about 1-2 weeks.

    Patients may have side effects from the conditioning treatments. These may include:

    The transplant team will watch for side effects. There are treatments to help prevent or manage them.

  4. Infusion of stem cells

    After conditioning, the donor cells are given to your child through a vein into the bloodstream. Donor cells are in a bag or syringe that is connected through a tube to your child's central line. This process is called an infusion. It is much like a blood transfusion. Your child is awake during the infusion. It only takes a few minutes to a few hours.

    Hematopoietic cell transplant illustration of female patient in hospital bed with saline and stem cells IV bags

    There are two basic types of transplants: allogeneic (blood-forming cells come from a donor) and autologous (the patient’s own cells are used). A patient receives cells from the donor through a vein in a process much like a blood transfusion. The cells travel through the bloodstream to the center of the long bones. The transplanted cells restore the patient’s ability to make healthy red blood cells, white blood cells, and platelets.

  5. Engraftment

    The goal of allogeneic transplant is for the donor's blood-forming stem cells to travel to the bone marrow and begin to divide to make more stem cells. The stem cells become white blood cells, red blood cells, and platelets. This is called engraftment. Engraftment may take 2-5 weeks. The time varies depending on the donor and stem cell product used. Patients may be given medicines to promote engraftment.

    During this time, your child will have frequent blood tests to monitor the numbers of red blood cells, white blood cells, and platelets.

    Neutrophils (a type of white blood cell) engraft first, followed by platelets and then red blood cells.

  6. Supportive care after transplant

    Patients receive supportive care during the bone marrow transplant process to help manage side effects. This may include:

    • Infusions of platelets and red blood cells
    • Medications to prevent or fight infection, such as antibiotics, anti-viral, or anti-fungal medicines
    • Medications to prevent nausea and vomiting
    • Pain medications
    • Nutrition support
    • Medications to prevent graft-versus-host disease (GVHD)

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Risks of an allogeneic transplant 

Some patients have few side effects. Others have serious complications that require long hospital stays. Some problems can be life-threatening.

Possible side effects that may occur soon after allogeneic transplant include:  

  • Side effects from chemotherapy or radiation therapy used during conditioning or as part of treatment  
  • Infection because of a low white blood cell count (neutropenia)  
  • Weakness or fatigue caused by fewer red blood cells (anemia)
  • Increased risk of bleeding or bruising caused by low platelets (thrombocytopenia) 
  • Graft failure or rejection if the cells do not grow well or are destroyed
  • Problems with the heart, lung, kidneys, liver, or other organs

After the new donor cells have grown, other risks include:

  • Graft-versus-host disease (GVHD) may occur if the donor cells see the patient's normal cells as different and attack them. Other immune system problems can also occur.
  • Infections are an ongoing risk for several months as the new donor cells grow and mature.
  • Disease relapse or progression may occur if treatments are not successful.
  • Long-term or late effects may develop due to the transplant or any treatments a patient received before transplant.

Taking care of your child after allogeneic transplant

Important points to keep in mind:

  • Your child will stay in the hospital for at least a month after admission for treatment.
  • Watch for signs of infection or illness. Call your doctor if your child develops a fever or symptoms such as rash, nausea, vomiting, diarrhea, abdominal pain, mouth sores, bruising or bleeding, trouble breathing, headache, or other change in condition.
  • Your child will have a very weak immune system for weeks after the transplant. Take steps to prevent infection. Avoid public areas, wash hands often, stay away from people who are sick, and wear a mask as instructed. Limit visitors and screen for signs of illness.
  • Give medicines as instructed. Let your care team know if your child has any problems taking medicines or keeping them down.
  • Follow your child's mouth care plan.
  • Make sure your child has a daily bath.
  • Encourage your child to be active throughout the day as tolerated.
  • Let your care team know if you have questions or concerns.
  • Avoid sun exposure when possible. Protect the skin from the sun and use sunscreen with a SPF of 30 or higher.

Key Points

  • Allogeneic transplant steps include pre-transplant testing and evaluation, conditioning, infusion, engraftment, and monitoring for side effects of the transplant process.
  • An allogeneic transplant uses blood-forming stem cells (hematopoietic stem cells) from another person, called a donor.
  • After the conditioning treatment, the stem cells are given to the patient through an infusion.
  • The donor's infused stem cells travel to the patient's bone marrow and begin to divide to make new stem cells.
  • The blood-forming stem cells become white blood cells, platelets, and red blood cells.

–
Reviewed: August 2022

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