Transcript No Slide Title

Anthony Nolan Research Institute
KIR POLYMORPHISM
Christian Garcia, MD
NK cell
Target
Image by Dr. G. Arancia and K. Malorni, Rome
Critical component of the innate immune system to a great variety
of pathogens including virus, fungi, parasites and bacteria.
Important mediators of anti-tumoral immunity.
Comprise approximately 10% of all peripheral blood lymphocytes.
Cytologically known as Large Granular Lymphocytes.
Lack clonally expressed antigen receptors encoded by
rearranging genes.
Natural Killer cells have evolved several receptor systems to carry out their
function of detecting and eliminating pathogen infected cells and tumour
cells during the prolonged period required for the clonal expansion of
antigen-specific B and T cells
NKG2s (C-type lectin-like)
 NCR (Natural Cytotoxicity Receptors)
KIRs (Immunoglobulin-like)
 NKG2s (C-type lectin-like)
NCR (Natural Cytotoxicity Receptors)
 KIRs (Immunoglobulin-like)
Killer Immunoglobulin-like receptors (KIR) are polymorphic cell surface
molecules present on Natural Killer (NK) cells and a small subset of T cells
(NKT cells).
 KIRs (Immunoglobulin-like)
They recognise classical HLA class I molecules with allotype specificity.
They are the most polymorphic receptor system expressed by NK cells.
First lymphocytes to engraft after a HSCT.
Present 7 days post-transplant, their cytolytic and proliferative
activity peaks 30-50 days post-transplant.
One month after the HSCT, they make up 50-90% of the total
circulating lymphocyte population.
The existence of NK cell receptors capable of mediating specific
allorecognition was established in 1990 by Moretta A. et al.
Studies regarding NK cell roles in HSCT have produced
controversial results in relation to the level of KIR matching
necessary to allow for optimal engraftment and potent GvL while
maintaining the level of GvH reactions to a minimum.
KIR2D
KIR3D
KIR genes and proteins are classified and named on the
basis of structure and sequence homology.
KIR2D
KIR3D
KIR proteins can have two or three extracellular Immunoglobulin(Ig)-like
domains.
KIR gene & protein names start with “KIR” followed by a digit indicating
the number of Ig-like domains followed by a “D” (domain)
KIR2DL
KIR2DS
KIR3DL
KIR3DS
Each of these KIR proteins can also have dimorphic cytoplasmic tails.
In nomenclature KIR2D or KIR3D is followed by a letter “L” or “S”
indicating the presence of a “Long” or “Short” cytoplasmic tail.
*Pseudogenes have a “P” instead of an “L” or “S” (KIR2DP1 & KIR3DP1)
KIR2DL
KIR2DS
KIR3DL
Long cytoplasmic tails have ITIMs which
generate inhibitory signals.
KIR3DS
KIR2DL
KIR2DS
KIR3DL
KIR3DS
Short cytoplasmic tails generate activating signals.
KIR2DL1
KIR2DL2
KIR2DL3
A final digit indicates the number of the gene
encoding a protein with this structure in the order it
was discovered.
This constitutes the GENE NAME or LABEL
KIR2DL1
KIR2DL2
KIR2DL3
Although the nucleotide and protein sequence
between these three KIR genes may be very similar,
genetic segregation in families has shown them to be
different genes.
KIR2DL1
KIR2DL1*001
KIR2DL1*002
KIR2DL1*003
KIR2DL1*004
KIR2DL1*005
Because these KIR genes are known to be polymorphic, the
presence of allelic variants which lead to a protein change
are further detailed by adding to the gene name a separator
followed by a digit.
KIR2DL1
KIR2DL1*001
KIR2DL1*002
KIR2DL1*003
KIR2DL1*004
KIR2DL1*005
KIR2DL1*00301
KIR2DL1*00302
Finally, if two different nucleotide sequences code for the
same protein, such synonymous differences are indicated
with two final digits.
KIR2DL1
KIR2DL1*001
KIR2DL1*002
KIR2DL1*003
KIR2DL1*004
KIR2DL1*005
KIR2DL1*00301
KIR2DL1*00302
This KIR diversity is the result of several levels of
organisational complexity.
KIRs are encoded within a 150 Kb stretch of the leukocyte receptor
complex (LRC) on chromosome 19 (19q13.4).
The LRC constitutes a large (1 Mb), dense cluster of rapidly evolving
immune genes of relatively recent evolutionary origin.
First level of complexity: multiple KIR genes encoding different proteins.
The KIR gene family consists of 17 genes.
Different KIR genes are organised within this region as haplotypes.
Second level of complexity: several haplotypes containing unique
combinations of different KIR genes.
KIR haplotypes show extensive diversity characterised by variability in
the number of genes present.
Third level of complexity: Each of the different KIR genes is polymorphic
leading to multiple allelic variants.
15 KIR genes (plus 2 pseudogenes).
Third level of complexity: Each of the different KIR genes is polymorphic
leading to multiple allelic variants.
91 sequences
analysed and
aligned.
Third level of complexity: Each of the different KIR genes is polymorphic
leading to multiple allelic variants.
1 2
3
4
5
6
7
8
Most KIR genes have 9 exons.
KIR genes span approximately 1.2 Kb and are arranged in head to tail
fashion and separated by 2 Kb from each other.
9
KIR3D
1 2
3
4
KIR2D
KIR2D
(TYPE 1)
(TYPE 2)
5
6
7
8
9
KIR exons correspond approximately to the regions and domains of their
respective KIR proteins.
KIR3D
1 2
3
4
KIR2D
KIR2D
(TYPE 1)
(TYPE 2)
5
6
7
8
KIR exons 1 and 2 encode the leader peptide which is cleaved before
expression.
9
KIR3D
1 2
3
4
KIR2D
KIR2D
(TYPE 1)
(TYPE 2)
5
6
7
8
Exon 3 of KIR3Ds and type 2 KIR2Ds encodes for the membrane distal
domain (in type 1 KIR2Ds it is represented by a pseudoexon).
9
KIR3D
1 2
3
4
KIR2D
KIR2D
(TYPE 1)
(TYPE 2)
5
6
7
8
Exon 4 of KIR3Ds and type 1 KIR2Ds encodes for the middle domain
(this exon is absent in type 2 KIR2Ds).
9
KIR3D
1 2
3
4
KIR2D
KIR2D
(TYPE 1)
(TYPE 2)
5
6
7
Exon 5 encodes the membrane proximal domain of all KIRs.
8
9
KIR3D
1 2
3
4
KIR2D
KIR2D
(TYPE 1)
(TYPE 2)
5
6
7
Exon 6 and part of exon 7 encode the stem region of all KIRs.
8
9
KIR3D
1 2
3
4
KIR2D
KIR2D
(TYPE 1)
(TYPE 2)
5
6
7
Part of exon 7 encodes the transmembrane region of all KIRs.
8
9
KIR3D
1 2
3
4
KIR2D
KIR2D
(TYPE 1)
(TYPE 2)
5
6
7
8
Part of exon 7, all of exon 8 and 9 encode the cytoplasmic region of all
KIRs.
9
Class I HLA
1
2
3
4
5
6 7 8
In classical Class I MHC most of the polymorphism is found in exons 2
and 3, which encode the peptide binding groove.
Class I HLA
2DL1
2DL3
2
1
4
3
5
6 7 8
1
2
() 3
4
5
6
7
8
9
1
2
() 3
4
5
6
7
8
9
1
2
3
4
5
6
7
8
9
1
2
3
4
5
6
7
8
9
3DL1
3DL2
KIR gene polymorphism is evenly distributed along the entire length of
the gene.
LIGAND BINDING LOOPS
In an attempt to establish the functional impact of the amino acid
substitutions observed in KIR proteins we analysed the nature of the
replacements.
TRANSMEMBRANE REGION
In an attempt to establish the functional impact of the amino acid
substitutions observed in KIR proteins we analysed the nature of the
replacements.
CYTOPLASMIC TAIL
In an attempt to establish the functional impact of the amino acid
substitutions observed in KIR proteins we analysed the nature of the
replacements.
LIGAND BINDING LOOPS
Crystallographic analysis have described the regions of KIR2Ds which
directly interact with their cognate HLA ligands.
LIGAND BINDING LOOPS
KIR2DL1 with HLA-Cw4
Q.R.Fan, E.O.Long & D.C.Wiley
10-May-01
LIGAND BINDING LOOPS
KIR2DL2 with HLA-Cw3
J.C.Boyington, S.A.Motyka, P.Schuck, A.G.Brooks & P.D.Sun
10-Feb-00
Twelve different KIR maps were generated, each comparing the
polymorphic residues representing allelic differences within a gene.
AMINO ACID REPLACEMENTS IN THE EXTRACELLULAR
DOMAINS OF KIR PROTEINS
Some KIR proteins have most of
their extracellular polymorphic
residues restricted to a single
domain.
In some cases two of these
polymorphisms are found in a
single allele and could potentially
relate to differential HLA-binding
properties, although this has yet to
be shown through binding assays.
KIR3DL1*004
AMINO ACID REPLACEMENTS IN THE EXTRACELLULAR
DOMAINS OF KIR PROTEINS
Some KIRs do have polymorphic
residues in their HLA-binding
region and in close proximity
(<5Å) to the putative HLA-ligand.
This is the case of:
-KIR2DS1
-KIR2DS4 and
-KIR3DL1.
70% of the replacements observed & classified according to their
charge were conservative.
53% of the replacements observed & classified according to their
polarity & volume were conservative.
65% of the replacements observed & classified according to their
hydrophobicity were conservative.
This suggest a requirement to maintain a conserved
overall charge distribution in KIR proteins.
ANTHONY NOLAN RESEARCH INSTITUTE
HLA INFORMATICS GROUP
Steven G.E. Marsh, BSc PhD ARCS
James Robinson, BSc MSc
Christian Garcia, MD
Prof. J. Alejandro Madrigal, MD PhD FRCP MRCPath DSc