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HLA and more
Ilias I.N. Doxiadis
Geneva – 03/04/2012
www.ebmt.org
HLA and more
HLA and more / Doxiadis
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Topic of the day
Compatibility testing is a type of testing used to ensure
compatibility of the system/application/website built
with various other objects such as other web browsers,
hardware platforms, HLA and more…
KISS = Keep It Short and Simple
What is HLA?
• Human Leukocyte Antigens
• Expressed on almost all nucleated cells
(red cells have remains of some HLA
molecules (Blood group BG = HLA-B7;
platelets express HLA (megakaryocytes )
• Plays a key role in immune response (navel
of the immune world) and in some other
things
What is immunogenetics?
• Polymorphic (variable) genes involved in
immune action
• Mendelian inheritance (green peas story
of the Czech monk)
Scientists on this field are enthusiastic!
HLA
• Originally detected as blood groups present on
white blood cells (Human Leuk(c)ocyte
Antigens) but present on almost all nucleated
cells and platelets.
• More polymorphic than red blood groups:
ABO system: 4 possible combinations (A,B,AB, O)
HLA system: >1 million combinations (linkage
disequilibrium)
HLA antigens (leading to an antibody
production)
ABO natural antibodies
HLA only antibodies after confrontation (!)
with foreign HLA antigens i.e. pregnancy,
blood transfusion and transplantation
(* post SCT problems)
1954: antibodies can cause leukocyte agglutination
HLA:
Human Leukocyte Antigens
Complement-dependent cytotoxicity
Negative reaction
Positive reaction
CDC
Serological difference between HLA-B35 and B53
B*35:01 = B35 (Bw6)
AA pos.
77
80
81
82
83
B*35:01
Ser Asn Leu Arg Gly
B*53:01
Asn Ile Ala Leu Arg
B*53:01 = B53 (Bw4)
Human Leucocyte Antigens
DNA Typing:
DNA (from any suitable source) is amplified
using specific primers. The needed level of
resolution defines the method to be used.
Allelic difference between HLA-B*35 and B*53
N
B*35:01
77
80
81
82
83
AGC AAC CTG CGC GGC
B*53:01
AAC ATC GCG CTC CGC
Polymorphism of the HLA system
A
Specificities:
C
B
DR DQ
A*01
B*51
DR*01
A*02
B*07
DR*15
A*03
B*08
DR*03
A*11
B*44
DR*04
A*69
B*15
DR*07
etc
etc
etc
DP
Chromosome 6
A
C
B
Chromosome 15
HLA class I molecules present on all nucleated
cells and platelets
Beta-2
microglobulin
Chromosome 6
DR
αβ
DQ
αβ
DP
αβ
HLA class II molecules, mainly expressed on antigen presenting
cells: dendritic cells, monocytes, B-cells and activated T cells
A1
B8
DR3
A2
B12
DR4
A3
B7
A9 B60
A1
B8
A3
B7
DR2
DR5
DR3
DR2
Genetics of HLA: mendelian inheritance; codominant expression
Haplotype:
set of HLA genes on one chromosome
Phenotype:
set of antigens expressed on the cells
Genotype:
set of genes on the DNA
cd
ab
ac
25 %
ad
bc
HLA haploidentical
50 %
HLA different
HLA identical
ac
bd
25 %
The HLA system
>7,000 HLA alleles
monomorphic sites
T cell recognizes target cell
T cell starts to destruct target cell
Function
Lysis of target cell
Role of HLA in the immune
response
patient
APC
HLA I
IgG
HLA II
antibodies
CD8+
B
CD4+
T
T
cytotoxic T cell
helper T cell
HLA class I /self peptide
No recognition
CD8+ T cell
Viral protein
virus
HLA class I /viral peptide
Recognition
CD8+ T cell
Self protein
APC
HLA class II
Not recognized
CD4+ T cell
virus
APC
HLA class II
Activation
CD4+ T cell
Clinical consequence of HLA
polymorphism
Viral protein
Viral peptide
HLA-A1
+
HLA-A2
+
HLA-A3
+
HLA-A11
--
Polymorphism HLA is clinically relevant
• Different HLA molecules bind
different peptides presented to T cells
• HLA associations with infectious
diseases (e.g. B53)
• HLA associations with auto-immune
diseases i.e. ankylosing spondylitis
(B27), diabetes, rheumatoid arthritis
Characteristics of MHC molecules: Enormous polymorphism
Consequence: differential
binding of antigenic
peptides and differential
immune response to
pathogens.
Increased incidence of
heterozygosity
Consequence: more
possibilities for peptide
binding and broader
immune response
Question: How and why did MHC polymorphism
evolve?
Analysis of HLA
alleles in different
populations
New HLA class I alleles in
Amerindians
Variation is
induced in
the groove
Hypothesis viral pressure leads to selection new alleles
Gene frequencies HLA class I alleles
survivors versus controls
16
14
12
10
survivors
controls
8
6
4
2
0
A30
B7
B12
B17
Gene frequencies HLA class II alleles
survivors versus controls
30
25
20
survivors
controls
15
10
5
0
DR2
DR4
DR12
DR13
mismatches / matches /
incompatibilites
What is a mismatch?
P: HLA-A1, A2; B7, B8; DR2, DR3
D: HLA-A1, A2; B7, B15; DR2, DR3
MM ?
P: HLA-A1, A2; B7, B8; DR2, DR3
D: HLA-A1,-; B7, B8; DR2, DR3
MM ?
P: HLA-A1, A2; B7, B8; DR2, DR3
D: HLA-A3,-; B7, B8; DR2, DR3
MM ?
What is a mismatch?
P: HLA-A1, A2; B7, B8; DR2, DR3
D: HLA-A1, A2; B7, B15; DR2, DR3
D>P
MM ?
no
P: HLA-A1, A2; B7, B8; DR2, DR3
D: HLA-A1,-; B7, B8; DR2, DR3
D>P
MM ?
yes
P: HLA-A1, A2; B7, B8; DR2, DR3
D: HLA-A3,-; B7, B8; DR2, DR3
D>P
MM ?
yes
SCT
• T cell mediated response
• By introduction of incompatibilties
humoral response possible
• Post transplantation treatment of the
patient requires the control of HLA
specific antibodies in the donor and the
patient
Immunogenetics and ..
fun
Rhodents prefer partners with
dissimilar MHC
Different H-2
80%
Recognition based on odour:
H-2 identical
20%
similar results when urine is used
Yamazaki et al., 1979
Do the MHC genes play a role in partner choice?
MHC-dependent mating preferences
in man (Wedekind et al., 1995)
•Female (N=49) and male students (N=44)
were typed for HLA-A,-B and –DR.
•The male students had to use neutral soap
and no after-shave etc.
•Each male student wore a T-shirt for two
consecutive nights.
•Next the T shirts were collected but not
washed
T-shirts are put in a box and females are asked to smell
Each women is asked to judge the odour of 7 T-shirts:
• 3 of man with a similar HLA type.
• 3 of man with a dissimilar HLA type.
• 1 control (fresh) T shirt.
Females prefer odour of males with
dissimilar HLA types
very nice
Pill using women
6
5
4
3
2
1
terrible
0
HLA
dissimilar
HLA similar
HLA
dissimilar
HLA similar
Wedekind et al.,1995
Females prefer odour of males with
dissimilar HLA types
very nice
Pill using women
6
5
4
3
2
1
terrible
0
HLA
dissimilar
HLA similar
HLA
dissimilar
HLA similar
Wedekind et al.,1995
Summary and conclusions
• To work in the field of immunogenetics is
really rewarding
• The function of the molecules is the
immune surveillance towards pathogens
• Transplantation reflects all attributesof
immunity
• Among all these factors is HLA one of the
major components.
Stem cells and diseases….
The end !
Thank you