What is a stem cell transplant?

By now you have probably heard the terms ‘stem cell transplant’, ‘bone marrow transplant’ or ‘haemopoietic stem cell transplant’ mentioned a few times, but you might not be 100% sure what it involves. If you have a condition that affects your bone marrow or blood, it could be the best treatment option. 

During a stem cell transplant your medical team will put new, healthy stem cells into your bloodstream. After a period of time they will attach to your bone marrow (called engraftment) and start to make new blood cells. Your new stem cells will be selected from a donor that is closely matched to you – to give you the best possible chance of overcoming your condition.

In this section we answer the following questions:

• What are stem cells?
• What are the different types of blood cells and what do they do?
• What's the difference between a stem cell and a bone marrow transplant?
• How do transplants work?

What are stem cells?

Stem cells are the body’s primary cells. All other cells, tissue, organs and bones develop from stem cells.

Blood stem cells, found in our bone marrow, are responsible for creating lots of different types of blood cells. They all have a unique job to do that keeps our blood healthy.

Our blood stem cells need to produce exactly the right amount of each type of blood cell. If this carefully-controlled process goes wrong, it can result in your blood having too many cells that are not fully developed. This can in turn lead to blood cancers or blood disorders.

What are the different types of blood cells and what do they do?

• Red blood cells: the most abundant type of blood cell. They carry oxygen to all the tissues in your body. You might also hear them referred to as ‘erythrocytes’. If you have too few red blood cells or they don’t function properly, it can cause anaemia.
• White blood cells: the cells that make up your immune system and fight infections. They can be divided into further groups based on the jobs they do.
• Neutrophils: one of the first cell types to respond to infections as they enter the body. Neutrophils are the most abundant type of white blood cell. When they travel to the site of an infection, it often causes inflammation and swelling.
• Lymphocytes: there are two main types of these white blood cells – T cells identify foreign invaders and recruit other immune cells to help, while B cells produce and secrete antibodies.
• Plasma cells: mature B cells that produce different types of antibodies to help fight infection. When problems occur with their production and development it can lead to myeloma.
• Platelets: they help the blood to clot following injury or trauma.

What's the difference between a stem cell and a bone marrow transplant?

Both types of transplant give the same result – the patient receives stem cells that will develop into a new immune system. The only difference is how the cells are collected from the donor.

For 90% of donations, stem cells are collected through the donor’s bloodstream in a process called peripheral blood stem cell collection (PBSC). Their blood is passed through a small tube into a machine that collects the stem cells, and then returns the rest of the blood to the body. It’s a very similar experience to giving blood but takes a little longer.  

For 10% of donations, the stem cells are collected from the donor’s bone marrow. It involves a small surgical procedure, using a needle to collect bone marrow from the donor’s pelvis under general anaesthetic.

The choice of collection method depends on the condition involved, the patient’s general health and age. The doctor will assess which method is most appropriate for you.

If you would like more information on how stem cells are collected, or if you are a friend or family member who is thinking of joining the register, our ‘How to be an Anthony Nolan stem cell donor’ video can help.

How do transplants work?

First, you’ll have treatment to get rid of the abnormal cells that are the cause of your condition using chemotherapy and sometimes radiotherapy. This is called conditioning therapy. The day after this finishes, your new stem cells will be infused into your blood in a similar way to a regular blood transfusion.

When your new stem cells enter your blood, they will move to your bone marrow and start producing new blood cells. Over time, this leads to the development of your new immune system that can recognise and remove any remaining abnormal cells in your body. It will also protect you against things like bacteria and viruses that can cause infections.

Information published: 26/04/2018
Next review due: 26/04/2021