Understanding Thymus Transplantation
What Is the Thymus?
The thymus is like a schoolhouse attended by stem cells, immature white blood cells from bone marrow that develop into functioning T cells. After about six months, a small percentage of the developing T cells leave the thymus to become normal T cells that protect the infant by fighting off infection and not attacking the infant’s organs.
Tissue Removed During Heart Surgery
When the thymus is present at birth, it is located on top of the heart. If an infant with a thymus requires heart surgery, the surgeon may remove a portion of the thymus to operate on the part of the heart that is underneath the thymus. This removed thymus tissue may be used for transplantation after permission is obtained from the infant’s parent(s).
What Is Thymus Transplantation?
Thymus transplantation is an investigational procedure that uses thin slices of thymus tissue to build the immune system of an infant born without a thymus. This can occur when a child is born with complete DiGeorge syndrome, a genetic disorder that can also cause other medical concerns, including a heart defect and/or calcium problems. Some infants with DiGeorge may have problems with vision and hearing, blockage of one or both nasal passages, and abnormal ears.
If Successful, Infection-Fighting T Cells Develop
The donor thymus used for thymus transplantation is cut into thin slices and kept in the laboratory while testing is done on blood from the donor infant and their mother. The testing ensures the thymus donor does not have an infection that could harm the infant with complete DiGeorge syndrome. The thin slices of thymus tissue are then implanted into the thigh muscle of the infant born without a thymus who has complete DiGeorge syndrome. Tiny blood vessels called capillaries grow from the muscle into the thymus tissue, providing oxygen and nutrients. If the procedure is successful, the infant develops T cells that can fight infections within about six to nine months.