Difference Between Autologous and Allogeneic Stem Cell Transplant

Stem cell transplantation is a major medical advancement used to treat various diseases, including blood cancers, immune system disorders, and inherited genetic conditions. Stem cells have the unique ability to divide and differentiate into specialised cells, making them essential for replacing damaged or diseased tissues in the body. Two major types of stem cell transplantation used in clinical practice are autologous and allogeneic. Although both aim to restore healthy bone marrow and immune function, they differ in terms of donor source, immune response, risks, and applications.

1.0What Are Stem Cells?

• Stem cells are undifferentiated cells that can divide and differentiate into specialised cell types, such as red blood cells, white blood cells, platelets, and tissue cells. 
• They help maintain and repair damaged tissues in the human body.
• Stem cells used in transplantation are commonly obtained from:
• Bone marrow
• Peripheral blood
• Umbilical cord blood
• Stem cell transplants are also known as hematopoietic stem cell transplants (HSCTs), as they restore blood-forming tissues.

2.0What Is an Autologous Stem Cell Transplant?

An autologous stem cell transplant is a medical procedure where stem cells are collected from the patient’s own body and later returned after high-dose treatment such as chemotherapy or radiation therapy. The word “autologous” means “derived from the same individual.”

Key Features of Autologous Transplant

• The patient is the donor and recipient.
• Stem cells are collected before treatment and frozen for later use.
• Used mainly when the body's immunity does not need external donor cells.

Procedure Steps

1. Stem Cell Collection: Patient’s stem cells are extracted from bone marrow or peripheral blood.
2. Processing and Storage: Cells are purified and preserved in liquid nitrogen.
3. Conditioning Therapy: High-dose chemotherapy or radiation destroys abnormal cells.
4. Stem Cell Infusion: Stored stem cells are reintroduced into the bloodstream.
5. Recovery: Stem cells gradually begin producing healthy blood cells.

Uses of Autologous Transplants

Autologous transplants are commonly used in:

Advantages

• No risk of graft-versus-host disease (GVHD).
• No need for donor matching.
• Lower rejection risk.

Limitations

• Possibility of reintroducing cancerous or abnormal cells.
• Immune recovery may take time.

3.0What Is an Allogeneic Stem Cell Transplant?

An allogeneic stem cell transplant involves receiving stem cells from a genetically matched donor. The word “allogeneic” means “from another individual of the same species.”

The donor can be:

• A sibling or family member (related donor)
• A matched volunteer (unrelated donor)
• Umbilical cord blood donor

Key Features of Allogeneic Transplant

• Cells are obtained from a separate, genetically matched donor.
• Requires strict HLA matching to reduce immunity-related complications.

Procedure Steps

1. Finding a Compatible Donor: HLA matching tests are performed.
2. Conditioning Treatment: High-dose therapy kills abnormal bone marrow cells.
3. Stem Cell Infusion: Donor stem cells are transferred to the patient.
4. Engraftment: Donor cells begin producing healthy blood cells.
5. Immune Monitoring: Preventing rejection and GVHD through medications.

4.0Uses of Allogeneic Transplants

Commonly used in:

Advantages

• Healthy donor immune cells can attack remaining cancer cells (graft-versus-tumour effect).
• No risk of reinjecting diseased cells.

Limitations

• Requires donor compatibility.
• Risk of graft-versus-host disease.
• Higher chance of immune rejection.

5.0Difference Between Autologous and Allogeneic Stem Cell Transplant

The major differences are summarized in the table below: