Preimplantation Genetic Diagnosis and HLA-Typing: The Potential for Selection of Unaffected HLA Matched Siblings
Haematopoietic stem cell transplantation (HSCT or bone marrow transplantation) is an effective treatment for many disorders of the haematopoietic system and has the potential to offer a cure for life. It is therefore an important treatment option, and for
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Bone marrow transplantation, or more correctly haematopoietic stem cell transplantation (HSCT), is an effective treatment for many disorders of the haematopoietic system. HSCT involves taking haematopoietic stem cells from a healthy donor and transferring them into an affected individual such that the recipient forms a new haematopoietic system that is free of disease. Although HSCT is most commonly used for haematological malignancies (acute and
L. Brown, BSc, Children’s Nursing () Department of Immunology and Bone Marrow Transplant, Paediatric Nurse Practitioner-Immunology and Bone Marrow Transplant, Great Ormond Street Hospital for Children NHS Foundation Trust, Great Ormond Street Hospital, Great Ormond Street, London WC1N 3JH, UK e-mail: [email protected] H.B. Gaspar, MBBS, MRCP(UK), MRCPCH, PhD Molecular Immunology Unit, Great Ormond Street Hospital and UCL Institute of Child Health, 30, Guilford Street, London WC1N, UK e-mail: [email protected] T. El-Toukhy, P. Braude (eds.), Preimplantation Genetic Diagnosis in Clinical Practice, DOI 10.1007/978-1-4471-2948-6_13, © Springer-Verlag London 2014
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chronic leukaemias and lymphomas), it is also used increasingly for the treatment of severe immunodeficiencies, specific metabolic diseases and haemoglobinopathies such as β-thalassaemia major and sickle-cell anaemia. If effective, HSCT has the potential to offer a cure for life and is therefore an extremely important treatment option and for some genetic conditions the only option available. The success of transplant is influenced by many factors but most importantly by the availability of a well-matched healthy donor to provide the source of donor stem cells. Numerous reports show that the best survival outcomes are achieved when a sibling who has the same genetic HLA type as the patient is available. PGD has the ability to identify many genetic characteristics of the embryo, including importantly the HLA type. For that reason, there has been increasing interest in the use of PGD techniques to select embryos that not only are genetically unaffected but are also an HLA match for older siblings who require a HSCT. The use of PGD and HLA typing is at present limited with just a handful of centres offering this service, and there have been few reports of successful births using this approach although the numbers are increasing. However, as the technology becomes more widely available, it is likely that PGD combined with HLA typing will be used to select healthy donors for a number of genetic disorders. This chapter will explain in more detail what HLA typing involves and the specific conditions where it may be applicable.
What Is HLA Typing? The human histocompatibility complex (HLA) is positioned on the short arm of chromosome 6 (Fig. 13.1). The HLA loci are part of the genetic region known as the major histocompatibility complex (MHC) which is fundamental for normal function and regulation of the immune response. The HLA complex is critical for the immune system to dist
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