Collection of Hematopoietic Stem Cells

What is hematopoietic stem cell collection?

Stem cell collection, also known as hematopoietic progenitor cell collection is performed by an apheresis procedure known as leukapheresis. It is used as a part of treatment to treat certain types of cancer and autoimmune diseases.

Stem cells are immature cells from which the different types of blood cells can grow. Stem cells are produced in the bone marrow, which is inside the bones. Small numbers of stem cells circulate in the blood stream, called peripheral blood stem cells.

The best time to collect peripheral blood stem cells is when the stem cells are at their highest levels in the blood. This is usually four to five days after your child receives specific medications — called growth factors — that stimulate cells to grow. These medications are prescribed by your child’s transplant physician at Children’s Hospital of Philadelphia.

Who needs hematopoietic stem cell collection?

If your child has neuroblastoma, a brain tumor, lymphoma or leukemia, your child’s doctor may recommend stem cell collection as part of your child's treatment.

Occasionally, peripheral blood stem cell collection is recommended for a child with certain genetic diseases that lead to autoimmune deficiency and anemia, or for patients undergoing gene therapy as part of a research study or treatment. 

Stem cell collection can be performed on babies, children and adults.

What to expect

For stem cell collection, your child’s blood will be withdrawn through a needle or catheter into a cell separator machine that separates the blood using a centrifuge. White blood cells containing stem cells are collected in a bag, while the rest of your child’s blood is returned through another vein or catheter. This procedure is called apheresis.

If your child has adequate veins for a large needle, an apheresis nurse will insert needles into the veins of both of your child’s arms to withdraw and return the blood. If your child has a central venous catheter (CVC) or port, blood will be withdrawn from one side, and returned to the other side.

Children who are especially small (weighing less than 25 Kg), or have anemia (low red blood cell count) will receive a blood transfusion with packed red blood cells (called blood prime) at the beginning of their stem cell collection procedure.

In addition, all children will receive a small amount of blood thinning medication called citrate to prevent their blood from clotting during the procedure. Citrate binds to calcium in the blood to lower your risk for clotting but may also cause low levels of calcium in the blood which can affect the heartbeat. Extra calcium is given during the procedure, usually through an IV, the prevent side effects known as citrate toxicity.

The cycle of drawing and returning your child’s blood is done simultaneously, so your child’s circulating volume remains stable.

Stem cell collection may take three to six hours to complete, depending on how many peripheral blood stem cells are required. In some cases, your child may need to return in the next day or two for additional stem cell collection. In most cases, after collection is complete, children can return to school or other activities within one day.

At the end of each procedure, the stem cell product will be taken to the Cell and Gene Therapy Lab at CHOP. 



Stem cell collection is a safe procedure, but side effects can occur. Your child may experience:

  • Symptoms similar to regular blood donation, such as fatigue, nausea, vomiting, dizziness or fainting
  • Problems related to the anticoagulant, including sour taste in the mouth, tingling around the lips and fingers, muscle cramping, irregular heartbeat, or prolonged bleeding
  • Bruising, numbness, pain or infection at the site of the needle stick or catheter insertion
  • Low or fluctuating blood pressure
  • Reactions related to a blood transfusion (if needed), including itching, rash, hives, shortness of breath, back pain or fever

The procedure may lower your child’s platelet count. The Apheresis physician will carefully monitor platelet counts and transfuse platelets as needed to prevent potential bleeding. 

Serious complications including abnormal heart rate, seizures and severe allergic reactions are extremely rare, but can occur.

If your child experiences any of these symptoms, please tell your child’s medical team.


If your child is having stem cell collection before other treatment — such as chemotherapy, radiation or organ transplant — the stem cells may be frozen and stored. After treatment, the stem cells may be reinfused into your child's body. The stem cells will boost your child’s immune system and help regrow body cells.

There are no direct benefits for stem cell donors who are not reinfused with their own cells.