HLA-haplotypes and the Blood Transfusion vs. Bone Marrow/Organ Transplantation paradox

Source

Explain the following dichotomy &/or paradox :-

Q. Why is it that while blood donations between family members (in other words, those individuals who share HLA-haplotypes) are discouraged, bone-marrow/organ transplantations are encouraged between them?

Background keywords :-

• blood (a type of connective tissue) – blood relative – HLA haplotype sharing – donor lymphocyte attack on host cells – transfusion associated graft versus host disease (TAGVHD) – blood donation from family donors contraindicated unless products irradiated
• organ donation – allogeneic bone marrow transplantation – closely matched HLA donor – family donor – host versus graft reaction or graft rejection – acute & chronic graft versus host disease (GVHD) – leukemias – graft versus leukemia effect – donor lymphocyte infusion – reduced intensity bone marrow transplantation

Apparently, GVHD is not so much of a problem in bone-marrow/organ transplantation when compared to blood transfusion. In fact, the graft versus leukemia effect (a type of GVHD), coupled with donor lymphocyte infusion, is used to our advantage in ‘reduced intensity bone marrow transplantation’ for the treatment of leukemias. Why the difference?

Background books:-

• Davidson’s Principles & Practice of Medicine 20 ed
  • Part 2 PRACTICE OF MEDICINE > 24 Blood disorders > BLOOD PRODUCTS AND TRANSFUSION > ADVERSE EFFECTS OF TRANSFUSION
  • Part 2 PRACTICE OF MEDICINE > 24 Blood disorders > HAEMATOLOGICAL MALIGNANCIES > LEUKAEMIAS
• Harrison’s Principles of Internal Medicine 16 ed

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“Millions saw the apple fall, but Newton was the one who ASKED WHY.”
~ Bernard Mannes Baruch
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