London, UK and Antwerp, B July 2012

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STEM CELL
TRANSPLANTATION
AND HISTOCOMPATIBILITY
Dr. Ann Van de Velde, Haematologist

2. From HLA typing to immunogenetic profiling
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Drawing Apparatus - Copyright: Robert Howsare

3. Goal
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Investigate structural differences between HLA
alleles
Find the best donor/recipient match for
hematopoietic stem cell transplation

4. The Haematopoietic System
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5. A good match (1/2)
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 Our immune system attacks things it doesn’t
recognize, including cells and tissues.
 Stem cell transplants can be rejected by the
recipient's immune system.
 Therefore, the transplanted stem cells must match
the recipient closely enough that they won't be
recognized as intruders.

6. A good match (2/2)
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 To determine whether the donor is a good
immunological match with the recipient, a tissue
typing test is performed using blood samples from
both individuals.
 This test identifies certain proteins, called HLA
antigens, which reside on the surfaces of specific
immune cells.
 If the donor and the recipient have identical HLA
antigens, they are a good match.

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8. 8

9. 46 XY – 46 XX
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10. The beginnings
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11. DNA
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Although 99.9% of human
DNA sequences are the
same in every person,
enough of the DNA is
different to distinguish one
individual from another,
unless they are
monozygotic twins.

12. Beyond the Double Helix
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 Human Genome Project (HGP) 2004
 There are approximately 23,000 genes in human
beings
 Understanding how these genes express themselves
will provide clues to how diseases are caused.

13. What is HLA?
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 Human Leukocyte Antigens
 The proteins encoded by HLAs are those on the
outer part of body cells that are unique to that
person.
 Plays a key role in immune response
 More polymorphic than red blood groups
 ABO system: 4 possible combinations (A, B, AB, O)
 HLA system: > 1 million combinations

14. HLA antigens
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 =>antibody production
 ABO: natural antibodies
 HLA: not-natural antibodies:
as a result of an immunologic challenge of a foreign
material containing non-self HLAs via
 Pregnancy
 Blood transfusion
 Transplantation

15. Origins – Jean Dausset (F)
Nobel Prize in Physiology and Medicine in 1980
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 1954: anti-leucocyte agglutinating substance
 1958: isoantibody specific to leucocytes
 1965: all leucocyte antigens = part of complex
 1968: renamed HLA
 1980: Nobel Prize
 => made it feasible to publish the first genetic map and,
later on, the first physical map of the human genome.

16. Histocompatibility
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 HLA typing
 Screening and identification of HLA antibodies
 Polymorphism of HLA represents a major barrier to
hematopoietic stem cell (HSC) transplantation.

17. DNA profiling (°10/09/1984, UK)
= DNA testing = DNA typing = genetic fingerprinting
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 not = full genome sequencing
 repetitive ("repeat") sequences that are highly
variable
 variable number tandem repeats (VNTRs)
 short tandem repeats (STRs)
 Siblings:
 VNTR loci are very similar
 Unrelated individuals:
 VNTR loci are very different

18. Variations of VNTR allele lengths
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in 6 individuals

19. HLA
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2 Classs: I and II
 Each class of HLA is represented by more than one
locus (polygeny).
 class I loci are HLA-A,-B and –C
 class II loci HLA-DR, -DQ and -DP.
 All the HLA genes map within a single region of the
chromosome (hence the term Complex).

20. Homologous chromosomes (diploid)
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21. Homologous chromosomes (diploid)
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22. Chromosome 6
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The HLA complex is located within the
6p21.3 region on the short arm of human
chromosome 6 and contains more than
220 genes of diverse function.
Many of the genes encode proteins of the
immune system.

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25. Haplotypes
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26. Alleles
different forms of a gene/genetic locus
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27. Allelic variation at a gene locus
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WHO Nomenclature Committee for Factors
of the HLA System
> 7000 alleles

28. Haplotypes
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 All loci are expressed co-dominantly, that is to say
both the set of alleles inherited from one's father
and the set inherited from one's mother are
expressed on each cell.
 The set of linked alleles found on the same
chromosome is called a haplotype.

29. Homozygous and heterozygous
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30. 30

31. MHC class I
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locus #
Major Antigens
HLA A 1,884
HLA B 2,490
HLA C 1,384
Minor Antigens
HLA E 11
HLA F 22
HLA G 49

32. MHC class II
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Theor.
HLA -A1 -B1 -B3 to -B5 1
possible
combination
locus # # # s
DM- 7 13 91
DO- 12 13 156
DP- 34 155 5,270
DQ- 47 165 7,755
DR- 7 1,094 92 8,302
DRB3, DRB4, DRB5 have variable presence in humans
1

33. Nomenclature applied to HLA
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 serological (antibody based) recognition
 e.g., HLA-B27 or, shortened, B27
 "HLA" in conjunction with a letter * and four-or-
more-digit number
 e.g., HLA-B*08:01, A*68:01, A*24:02:01N N=Null)

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35. Αλληλους / Allelos / "each other”
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36. GVH en GVL (1/2)
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 The most impressive impact of novel DNA typing
methods concerns matching for allogeneic HSC
transplantation because subtle serologically silent
sequence differences between allelic subtypes are
recognized by alloreactive T-cells with serious
consequences for graft outcome.

37. GVH and GVL (2/2)
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 Allogeneic stem cell transplantations have the
therapeutic effect of eliminating leukemia cells, with
the danger of developing graft versus host disease.
When donor and patient are HLA-identical, these
effects are due to minor histocompatibility antigens,
which are expressed from polymorphic genes.
Identifing which genes and which peptides cause the
GvL effect, without the development of GvHD.

38. Now the HLA-matched donor is ready
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to have her stem cells collected