Types of Bone Marrow Transplantation
Bone marrow transplantation or Hematopoietic Stem Cell Transplantation are of two types – allogenic or autologous.
Allogenic Transplantation
Allogenic transplantation refers to the procedure wherein bone marrow cells are obtained from a donor and injected into the patient, who is referred to as recipient.The donor may be related or unrelated to the recipient. The donor and recipient are matched before the transplantation for the presence of certain molecules called HLA or Human Leucocyte Antigens. Allogenic transplantation carries the risk of a Graft –versus- Host Disease (GVHD). It occurs due to a reaction of the immune cells from the graft against the recipient.The immune cells from the recipient can also react with the graft resulting in graft rejection. This reaction is normally suppressed by administering drugs called immunosuppressive drugs, which incapacitate the immune cells. The immunosuppressive drugs unfortunately depress the entire immune system, making the recipient susceptible to various infections. Allogenic transplantation between identical twins permits transplantation without the risk of graft – versus – host disease; this transplantation is also referred to as ‘Syngeneic Transplantation.’
Autologous Transplantation
Autologous transplantation is a procedure wherein hematopoietic stem cells or immature blood cells are drawn from the patient and reintroduced later. This procedure is often adopted in cancer patients requiring high doses of chemotherapy and/or radiotherapy. Bone marrow cells are very sensitive to radiation and chemotherapy. Hence, the cells are initially harvested and stored under required conditions. Once the patient completes the necessary treatment, the bone marrow cells are re-injected into the same patient. This procedure avoids the complication of graft-versus-host disease. However, if the harvested cells were contaminated with cancer cells, it also means that the cancer cells will be reintroduced in the patient following treatment. Nowadays, various methods like treating harvested cells with antibodies or chemotherapy before being reintroduced into the patient help to minimize this problem.
