A blood and marrow stem cell transplant is a procedure that replaces a person's faulty stem cells with healthy ones.
Stem cells are found in bone marrow, a spongy tissue inside the bones. Stem cells develop into the three types of blood cells that the body needs:
- Red blood cells, which carry oxygen throughout the body
- White blood cells, which fight infections
- Platelets, which help the blood clot
Small numbers of stem cells also are found in the blood and in the umbilical cord (the cord that connects a fetus to its mother's placenta).
Another type of stem cell, called an embryonic stem cell, can develop into any type of cell in the body. These cells aren't found in bone marrow.
Doctors use stem cell transplants to treat people who have:
- Certain cancers, such as leukemia, The high doses of chemotherapy and radiation used to treat some cancers can severely damage or destroy bone marrow. A transplant replaces the stem cells that the treatment destroyed.
- Severe blood diseases, such as thalassemias, aplastic anemia and sickle cell anemia. In these diseases, the body doesn't make enough red blood cells, or they don't work well.
- Certain immune-deficiency diseases that prevent the body from making some types of white blood cells. Without these cells, person can develop life-threatening infections. A transplant provides stem cells to replace the missing white blood cells.
Types of Stem Cell Transplants
The two main types of stem cell transplants are autologous and allogenic.
For an autologous transplant, patient's own stem cells are collected and stored for use later on. This works best when patient still has enough healthy stem cells, even patient is sick. If patient has cancer, the cancer cells are removed or destroyed from the collected cells.
For an allogenic transplant, patient get stem cells from a donor. The donor can be a relative (like a brother or sister) or an unrelated person. Patient also may get stem cells from umbilical cord blood donated by an unrelated person.
To prevent problems, the donor's stem cells should match with patient as closely as possible. Donors and recipients are matched through a blood test called HLA tissue typing.
What is Conditioning Regimen in Bone Marrow Transplant?
Conditioning regimens, also referred to as preparative regimens, are combinations of chemotherapy or radiation therapy designed to prepare the patient's body to receive the donor's bone marrow. The purpose of the conditioning regimen varies according to the type of stem cell transplant to be received by the patient.
For autologous transplants (transplant using patient's own cells), the conditioning regimen is designed so that increasing doses of chemotherapy with or without irradiation are administered to destroy more malignant cells.
For allogeneic transplants (patient gets stem cells from donor), the conditioning regimen is designed not only to destroy residual malignant cells, but also to provide immunosuppression to prevent the patient's body from rejecting the donor's stem cells.