Terms and Definitions

Understanding Transplant Terminology

At ASTCT, we know that learning that you or a loved one has cancer is scary — and the idea of a blood or marrow transplant can seem daunting. That's especially true when you're hearing terms you don't understand. Use this list of terms and definitions as a starting point — and never hesitate to ask your doctor for additional information.

Allogeneic Transplant

A type of transplant where a patient receives healthy blood-forming cells from a genetically non-identical donor. The healthy cells may come from a family member, an unrelated donor or umbilical cord blood.

Autologous Transplant

A type of transplant where a patient’s own blood-forming cells are collected, stored, and given back after chemotherapy and/or radiation therapy.


A process to collect a patient’s or a donor’s blood-forming cells from the blood stream before the transplant. This process may be used to collect autologous cells or allogeneic cells (related or unrelated).

Blood-Forming Cells

Cells that grow into red blood cells, white blood cells and platelets. These cells are also called blood stem cells or hematopoietic stem cells.

Blood-Forming Cell Sources

The 3 places where blood-forming cells are found are bone marrow, peripheral blood, umbilical cord blood. 

Graft-versus-Host disease (GVHD)

A common side effect of an allogeneic transplant that occurs because of differences between patient’s cells (host) and cells from the donor (graft). The new immune system from the donor may recognize the patient’s immune system as foreign and react. This reaction is called GVHD. All allogeneic transplant patients receive immune suppressive medications to try to prevent development of GVHD. All patients who develop signs and symptoms of GVHD receive additional immune suppressive therapy to treat this disorder. 

Acute GVHD usually occurs during the first 100 days after transplant and effects the skin, liver and gastrointestinal tract. 

Chronic GVHD usually occurs after 3 months post-transplant and may involve skin, joints, liver, mouth, gastrointestinal tract, lungs, eyes and other organ systems.

Human Leukocyte Antigen (HLA)

HLA typing is used to match patients and donors for allogeneic transplant. HLA are proteins (markers) found on most cells in the body. The patient’s immune system uses these markers to recognize which cells belong in the patient’s body and which cells do not. In an individual, half of the HLA markers are inherited from the mother and half from the father, so each brother and sister who shares the same parents as the patient has a 25% chance of being an HLA match. A close match between a patient’s and donor’s HLA markers is important for a successful transplant. HLA matching promotes the growth and development of new healthy blood cells (engraftment) and reduces the risk of GVHD.

Preparative Regimen

The process of preparing the patient’s body to receive the new blood-forming cells. This involves the use of high-dose chemotherapy with or without total body irradiation. 

Learn more about different diseases.

Diseases treatable by transplant:

Bone Marrow Failure Diseases:

Inherited Immune System Disorders:


Inherited Metabolic Disorders: