The IMGT/HLA database
James Robinson1, Kavita Mistry1, Hamish McWilliam2, Rodrigo Lopez2, Peter Parham3
and Steven G. E. Marsh1,4,*
1Anthony Nolan Research Institute, Royal Free Hospital, Pond Street, Hampstead, London, NW3 2QG,
2External Services, EMBL Outstation – European Bioinformatics Institute, Wellcome Trust Genome Campus,
Hinxton, Cambridge, CB10 1SD, UK,3Department of Structural Biology, Stanford University School of
Medicine, Sherman Fairchild Research Building, Stanford, California 94305-5136, USA and4Department of
Academic Haematology, UCL Cancer Institute, University College London, Royal Free Campus, Pond Street,
Hampstead, London, NW3 2QG, UK
Received September 13, 2010; Accepted October 6, 2010
It is 12 years since the IMGT/HLA database was
first released, providing the HLA community with
a searchable repository of highly curated HLA
sequences. The HLA complex is located within the
contains more than 220 genes of diverse function.
Many of the genes encode proteins of the immune
system and are highly polymorphic. The naming
of these HLA genes and alleles and their quality con-
trol is the responsibility of the WHO Nomenclature
Committee for Factors of the HLA System. Through
the work of the HLA Informatics Group and in collab-
oration with the European Bioinformatics Institute,
we are able to provide public access to this data
through the web site http://www.ebi.ac.uk/imgt/hla/
confirmatory sequences are dispersed to the HLA
community, and the wider research and clinical
The IMGT/HLA database was established to provide a
locus specific database (LSDB) for the allelic sequences of
the genes in the HLA system, also known as the human
Major Histocompatibility Complex (MHC). This complex
of >4 Mb is located within the 6p21.3 region of the short
arm of human chromosome 6 and contains in excess of
220 genes (1). The core genes of interest in the HLA
system are 21 highly polymorphic HLA genes, whose
protein products mediate the host response to infectious
disease and influence the outcome of cell and organ trans-
plants. With a nomenclature spanning over 50 genes
and currently over 5000 alleles, there is an obvious need
for a LSDB to curate these highly polymorphic variants.
The sequencing of HLA alleles began in the late 19700s
predominantly using protein-based techniques to deter-
mine the sequences of HLA class I allotypes. The first
complete HLA class I allotype sequence, B7.2, now
known as B*07:02:01, was published in 1979 (2). The first
HLA class II allele defined by DNA sequencing,
DRA*01:01, followed in 1982 (3). The first HLA DNA se-
quences or alleles were named by the WHO Nomenclature
Committee for Factors of the HLA System (4) in 1987. At
that time 12 class I alleles and nine class II alleles were
named: in the first 8 months of 2010 the Nomenclature
Committee was able to assign names to 1165 alleles.
The dissemination of new allele names and sequences is
of paramount importance in the clinical setting. The first
public release of the IMGT/HLA database was made on
the 16th December 1998 (5). Since then the database has
been updated every 3 months, in a total of 51 releases, to
include all the publicly available sequences officially
named by the WHO Nomenclature Committee at the
time of release.
The database was first available as the HLA Sequence
Databank (HLA-DB) (6), which allowed the periodic pub-
lication of HLA class I (7–10) and class II (11–16)
sequence alignments in a variety of journals. By 1995,
the first distribution of the HLA sequence alignments
was made online through the web pages of the Tissue
Antigen Laboratory at the Imperial Cancer Research
Fund (ICRF), London, UK. This work transferred to
the Anthony Nolan Research Institute (ANRI) in 1996
where it continues to this day as part of the IMGT/
HLA database and the hla.alleles.org web site.
IMGT/HLA data sources
The IMGT/HLA database receives submissions from
laboratoriesacross theworld(Figure 1). Thesesubmissions
are curated and analyzed, and if they meet the strict
requirements an official allele designation is assigned. The
IMGT/HLA database is the official repository for the
*To whom correspondence should be addressed. Tel: +44 20 7284 8321; Fax: +44 20 7284 8331; Email: email@example.com
Published online 11 November 2010Nucleic Acids Research, 2011, Vol. 39, Database issueD1171–D1176
? The Author(s) 2010. Published by Oxford University Press.
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/
by-nc/2.5), which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
WHO Nomenclature Committee for factors of the HLA
System, and is the only way of receiving an official allele
designation for a sequence. The sequence is then
incorporated into the next 3-monthly release of the
database. Since its release in December 1998 the database
has received nearly 9000 submissions, from around 600
submitters (Figure 1). These submissions come from a
variety of sources; the majority are from routine HLA
Typing laboratories or commercial organizations perform-
ing contract HLA typing for large haematopoietic stem cell
large-scale genome sequencing projects. All submissions
must meet strict acceptance criteria before the sequence
receives an official designation; ?3% of the submissions
received fail to meet these criteria and are rejected. In
addition, all the submissions received by the IMGT/HLA
database are also available from the EMBL-Bank/
GenBank/DDBJ collaboration (17–19). The EMBL-Bank
entries also contain database cross-references to the
The past few years have seen a dramatic increase in the
numbers of submissions seen and processed, with the
number of novel allele sequences identified each year
rising rapidly from around 300 in 2008 to over 1000 in
2009. This trend looks set to continue, with over 1200
novel alleles being reported in the first 9 months of 2010
(Figure 2). This is because of the increased affordability
and availability of the sequencing-based typing (SBT)
technology as the method of choice for HLA typing,
with the consequence of this high-resolution typing
being the determination of many novel HLA sequences.
A notable increase in volume has been from sequences
originating from China. Prior to 2008, the database only
had 28 submitters located in China; we now have over 70
submitters. The volume of submissions has also increased.
Up to 2008, we averaged only 18 submissions a year from
China, we are now averaging nearly 200 a year, a 10-fold
Another change in the data source has been the type of
submission received. In the early days of the database, we
received very few full-length or genomic sequences, now
with improved sequencing techniques we are getting a
much larger number of both full length and genomic
sequences covering a range of genes. These submissions
cover both new and confirmatory sequences, and the
database welcomes both. Confirmatory sequences are
important as they verify the existence of the single
nucleotide polymorphisms (SNPs) found in many novel
alleles. The confirmatory sequences often extend the
sequence of an allele beyond that currently held in
the database, where many alleles sequences only cover
the minimum length required. Over the last 2 years just
<40% of the submissions to the database have been
The increase in the number of submissions has also
seen a change in the type of new alleles seen. Over 97%
of new alleles now being submitted are derived from
SNPs. In contrast, in 2000, ?20% of new alleles identified
were based on motif shuffling. This is most likely due to
the methods used to identify alleles at this time that were
largely based on sequence-specific oligonucleotide probes
(20). Nowadays sequencing-based typing methods are
used extensively to perform HLA typing and this allows
for the easy identification of novel SNPs (Figure 3).
New HLA nomenclature
In April 2010, the official nomenclature used to name
HLA alleleswaschanged(21).The nomenclature
Figure 1. World map showing the source and volume of IMGT/HLA submissions by country.
D1172Nucleic AcidsResearch, 2011,Vol. 39, Database issue
changes were needed, as the existing system could no
longer cope with the number of allele variants found in
some allele families. The convention of using a four-digit
code to distinguish HLA alleles that differed in the
proteins they encoded was introduced in the 1987 HLA
Nomenclature Report (4). Since that time additional digits
have been added, and prior to the change, an allele name
could be composed of four, six or eight digits dependent
on its sequence. Each pair of digits was used to describe
the allele, the first two digits described the allele family,
which often corresponds to the serological antigen carried
by the allotype. The third and fourth digits were assigned
in the order in which the sequences had been determined.
Alleles whose numbers differed in the first four digits
differed by one or more nucleotide substitutions that
protein. Alleles that differed only by synonymous nucleo-
tide substitutions within the coding sequence were distin-
guished by the use of the fifth and sixth digits. Alleles that
only differed by sequence polymorphisms in introns or in
the 50- and 30-untranslated regions that flanked the exons
and introns were distinguished by the use of the seventh
and eighth digits. To deal with the ever increasing number
of HLA alleles described it was decided to introduce
colons (:) into the allele names to act as delimiters of the
For some users the changes to the nomenclature were
minor, to others like HLA Typing Laboratories and
Donor Registries, this change in nomenclature had a
major impact on their informatics systems. The IMGT/
HLA database helped to co-ordinate the move to the
new nomenclature by providing conversion lists and
tools to help identify alleles in both the new and old no-
menclature. The nomenclature officially changed on the
1 April 2010. To aid our users in preparing for this
change, the database provided conversion tables for
9 months prior to the release. These tables allowed users
to see what the changes would be and how they would
impact on their own systems. The database also provided
online tools for the conversion of allele names, as well as
links to external software designed for the conversion of
large data sets from the old to new nomenclature (22).
Further information on HLA nomenclature can be
found at the IMGT/HLA database’s sister site http://
hla.alleles/org. This site concentrates on HLA nomencla-
ture, whereas the IMGT/HLA database is more focussed
on sequence data. There is some overlap between the sites,
but with a different prime focus each site can deliver a
different set of data and downloadable content that may
not be suitable for the other.
Tools available at IMGT/HLA
The IMGT/HLA database provides a large number of
tools for the analysis of HLA sequences. These tools are
either custom written for the database or are incorporated
into existing tools on the EBI web site (23,24).
. Sequence alignments—access to alignment tool, which
filters pre-generated alignments to the users’ specifica-
tion. Provides alignments at the protein, cDNA and
. Allele queries—access to detailed information on any
HLA Allele, including information on the ethnic origin
of the source, database cross-references and seminal
through integration with EBI’s SRS search engine (25).
. Sequence search tools—integration into EBI’s suite of
search tools including FASTA (26) and BLAST (27).
. Downloads—access to a FTP directory containing all
the data from the current and previous releases in a
variety of commonly used formats like FASTA, MSF
. Cell Queries—a detailed a searchable database of all
the source material characterized in the submissions.
Figure 2. Graph of the number of submissions to the IMGT/HLA database by year. The recent surge in the number of submissions received by the
database is clearly shown. The values listed for 2010 are up to the end of September 2010, and do not represent a full year.
Nucleic AcidsResearch, 2011,Vol. 39, Database issueD1173
. Primer search tools—a simple search tool allowing
users to update primer hit pattern tables against each
release of the database.
. Ambiguous allele combinations—the use of SBT as
amethod for definingtheHLAtype iswell
documented, most SBT typing strategies currently
employed use the exons 2 and 3 sequences for HLA
class I analysis and exon 2 alone for HLA class II
analysis. Due to the heterozygous nature of the SBT
analysis the combinations of many pairs of alleles may
Figure 3. Heat maps of the polymorphic amino acid positions in HLA-B. The two sets of maps show the increase in the number of polymorphic
positions identified between the first release of the database in 1998 (A) and the latest release in 2010 (B). The x-axis is the amino acid position and
the y-axis the number of different amino acids seen at that position.
D1174 Nucleic AcidsResearch, 2011,Vol. 39, Database issue
give an ambiguous typing result. The document
includes a list of all alleles that are identical over
exons 2+3 for HLA class I and exon 2 for HLA
The challenge for the database is to keep up with the
continuing increase in sequence information, develop
new tools for the visualization of the sequences whilst
maintaining the high standards set in the presentation
and quality of the HLA sequences and nomenclature to
the research community. The database aims to continually
develop new tools and refine existing tools to meet this
challenge. Some of our planned future developments
include heat maps of polymorphic positions and a tool
for the graphical comparison of two allele sequences, to
highlight how changes to the DNA sequences affect the
protein structure and binding to proteins.
The IMGT/HLA database provides a centralized resource
for everybody interested, clinically or scientifically, in the
HLA system. The database and accompanying tools allow
the study of all HLA alleles from a single site on the
World Wide Web. It should aid in the management and
continual expansion of HLA nomenclature, providing an
ongoing resource for the WHO Nomenclature Committee.
The earliest version of the IMGT/HLA database,
December 1998, included only 964 alleles, covering 24
genes and was limited to much simpler tools and inter-
faces. The latest release, July 2010, contained over 5300
alleles for 34 genes, with this number set to grow as the
database continues to receive and name over a thousand
new alleles each year. The expansion of the database
content has been reflected in its use, in 1999 the web site
averaged just over 1500 visitors per month; in 2010 this
had increased to over 20000 visitors viewing over 50000
pages per month. The challenge for the database is to keep
up with this increase in sequences, develop new tools for
the visualization of the sequences whilst maintaining the
high standards set in the presentation and quality of the
HLA sequences and nomenclature to the research
The IMGT/HLA database is covered by the Creative
Commons Attribution-NoDerivs Licence, which is applic-
able to all copyrightable parts of the database, which
includes the sequence alignments. This means that users
are free to copy, distribute, display and make commercial
use of the databases in all legislations, provided they give
the appropriate credit (28,29). If users intend to distribute
a modified version of the data in any form, then they must
ask us for permission; this can be done by contacting
firstname.lastname@example.org for further details of how modified data
can be reproduced.
The authors would like to thank Angie Dahl of the Be The
Match Foundation, for her work in securing ongoing
funding for the database. They would like to thank all
of the individuals and organizations that support our
Bio-Rad; Gen-Probe, Invitrogen by Life Technologies;
European Federation for Immunogenetics; Innogenetics;
One Lambda Inc.; Olersup SSP; American Society for
Nolan; BAG Healthcare; Be the Match Foundation;
Innogenetics; the Marrow Foundation; the National
Cancer Research Fund, (now Cancer Research UK to
Funding for open access charge: Anthony Nolan, a
Conflict of interest statement. None declared.
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APPENDIX - ACCESS AND CONTACT
IMGT/HLA Homepage: http://www.ebi.ac.uk/imgt/hla/
IMGT/HLA FTP Site: ftp://ftp.ebi.ac.uk/pub/databases
D1176Nucleic AcidsResearch, 2011,Vol. 39, Database issue