Table 1.

Glossary of terms used in haematopoietic stem cell transplantation (HSCT)

Types of HSCT
Autologous HSCT (aHSCT)Transplantation of haematopoietic stem cells taken from patients and reinfused after high doses of cytotoxic therapy (usually chemotherapy with immunoablative therapeutic antibodies such as anti-thymocyte globulin [ATG] in patients with severe autoimmune diseases)
Allogeneic HSCTTransplantation of haematopoietic stem cells from a donor, either sibling or unrelated, and occasionally cord blood. Allogeneic HSCT is rarely performed for autoimmune diseases given the higher risks, and its use has been largely restricted to paediatrics
Sources of haematopoietic stem cells (HSC)
Peripheral blood stem cellsStem cells, labelled by the antigen CD34+, are mobilised using granulocyte colony stimulating factor (G-CSF) +/- chemotherapy from the bone marrow into the blood then harvested with apheresis
Bone marrowHaematopoietic stem cell source derived by direct aspiration of bone marrow, a stem cell source infrequently used now for autologous HSCT
HSCT phases
MobilisationMobilisation of CD34+ stem cells from the bone marrow into the peripheral blood using granulocyte colony stimulating factor (G-CSF) +/- chemotherapy. Stem cells are then harvested using leukapheresis
ConditioningHigh dose immunoablative or immunosuppressive regimen usually chemotherapy and therapuetic antibodies (for example antithymocyte globulin [ATG]) administered prior to stem cell infusion
HarvestingStem cells are harvested using leukapheresis
‘Transplant’/reinfusionThe thawing and reinfusion of the CD34+ cells into the patient
Aplastic phaseThe period when the immune system and haematopoietic system are unable to produce sufficient cells to maintain blood counts and innate immunity. The combination of antibiotic (prophylactic and therapeutic), transfusions, symptomatic care, growth factors and close monitoring required to bring the patient safely through and beyond engraftment, usually around 2 weeks post-transplantation
Supportive careThe combination of antibiotic (prophylactic and therapeutic), transfusions, symptomatic care, growth factors and monitoring required to bring the patient safely through and beyond engraftment, usually around 2 weeks post-transplantation
EngraftmentDefined as 3 days of neutrophils rising above 0.5 × 109/L and/or platelets rising above 20 × 109/L unsupported