Background: The antigen receptors, immunoglobulins (IG) and T cell receptors (TR), are specific molecular components of the adaptive immune response of vertebrates. Their genes are organized in the genome in several loci (7 in humans) that comprise different gene types: variable (V), diversity (D), joining (J) and constant (C) genes. Synthesis of the IG and TR proteins requires rearrangements of V and J, or V, D and J genes at the DNA level, followed by the splicing at the RNA level of the rearranged V-J and V-D-J genes to C genes. Owing to the particularities of IG and TR gene structures related to these molecular mechanisms, conventional bioinformatic software and tools are not adapted to the identification and description of IG and TR genes in large genomic sequences. In order to answer that need, IMGT^®, the international ImMunoGeneTics information system^®, has developed IMGT/LIGMotif, a tool for IG and TR gene annotation. This tool is based on standardized rules defined in IMGT-ONTOLOGY, the first ontology in immunogenetics and immunoinformatics. Results: IMGT/LIGMotif currently annotates human and mouse IG and TR loci in large genomic sequences. The annotation includes gene identification and orientation on DNA strand, description of the V, D and J genes by assigning IMGT^® labels, gene functionality, and finally, gene delimitation and cluster assembly. IMGT/LIGMotif analyses sequences up to 2.5 megabase pairs and can analyse them in batch files. Conclusions: IMGT/LIGMotif is currently used by the IMGT^® biocurators to annotate, in a first step, IG and TR genomic sequences of human and mouse in new haplotypes and those of closely related species, nonhuman primates and rat, respectively. In a next step, and following enrichment of its reference databases, IMGT/LIGMotif will be used to annotate IG and TR of more distantly related vertebrate species. IMGT/LIGMotif is available at http://www.imgt.org/ligmotif/.

IMGT®, the international ImMunoGeneTics information system® ( http://www.imgt.org ), was created in 1989 in Montpellier, France (CNRS and Montpellier University) to manage the huge and complex diversity of the antigen receptors, and is at the origin of immunoinformatics, a science at the interface between immunogenetics and bioinformatics. Immunoglobulins (IG) or antibodies and T cell receptors (TR) are managed and described in the IMGT® databases and tools at the level of receptor, chain and domain. The analysis of the IG and TR variable (V) domain rearranged nucleotide sequences is performed by IMGT/V-QUEST (online since 1997, 50 sequences per batch) and, for next generation sequencing (NGS), by IMGT/HighV-QUEST, the high throughput version of IMGT/V-QUEST (portal begun in 2010, 500,000 sequences per batch). In vitro combinatorial libraries of engineered antibody single chain Fragment variable (scFv) which mimic the in vivo natural diversity of the immune adaptive responses are extensively screened for the discovery of novel antigen binding specificities. However the analysis of NGS full length scFv (~850 bp) represents a challenge as they contain two V domains connected by a linker and there is no tool for the analysis of two V domains in a single chain. The functionality "Analyis of single chain Fragment variable (scFv)" has been implemented in IMGT/V-QUEST and, for NGS, in IMGT/HighV-QUEST for the analysis of the two V domains of IG and TR scFv. It proceeds in five steps: search for a first closest V-REGION, full characterization of the first V-(D)-J-REGION, then search for a second V-REGION and full characterization of the second V-(D)-J-REGION, and finally linker delimitation. For each sequence or NGS read, positions of the 5′V-DOMAIN, linker and 3′V-DOMAIN in the scFv are provided in the ‘V-orientated’ sense. Each V-DOMAIN is fully characterized (gene identification, sequence description, junction analysis, characterization of mutations and amino changes). The functionality is generic and can analyse any IG or TR single chain nucleotide sequence containing two V domains, provided that the corresponding species IMGT reference directory is available. The “Analysis of single chain Fragment variable (scFv)” implemented in IMGT/V-QUEST and, for NGS, in IMGT/HighV-QUEST provides the identification and full characterization of the two V domains of full-length scFv (~850 bp) nucleotide sequences from combinatorial libraries. The analysis can also be performed on concatenated paired chains of expressed antigen receptor IG or TR repertoires.

The adaptive immune system, along with the innate immune system, are the two main biological processes that protect an organism from pathogens. The adaptive immune system is characterized by the specificity and extreme diversity of its antigen receptors. These antigen receptors are the immunoglobulins (IG) or antibodies of the B cells and the T cell receptors (TR) of the T cells. The IG are proteins that have a dual role in immunity: they recognize antigens and trigger elimination mechanisms, to rid the body of foreign cells. The synthesis of the immunoglobulin heavy and light chains requires gene rearrangements at the DNA level in the IGH, IGK, and IGL loci. The rhesus monkey (Macaca mulatta) is one of the most widely used nonhuman primate species in biomedical research. In this manuscript, we provide a thorough analysis of the three IG loci of the Mmul_10 assembly of rhesus monkey, integrating IMGT previously existing data. Detailed characterization of IG genes includes their localization and position in the loci, the determination of the allele functionality, and the description of the regulatory elements of their promoters as well as the sequences of the conventional recombination signals (RS). This complete annotation of the genomic IG loci of Mmul_10 assembly and the highly detailed IG gene characterization could be used as a model, in additional rhesus monkey assemblies, for the analysis of the IG allelic polymorphism and structural variation, which have been described in rhesus monkeys.

The adaptive immune response provides the vertebrate immune system with the ability to recognize and remember specific pathogens to generate immunity, and mount stronger attacks each time the pathogen is encountered. T cell receptors are the antigen receptors of the adaptive immune response expressed by T cells, which specifically recognize processed antigens, presented as peptides by the highly polymorphic major histocompatibility (MH) proteins. T cell receptors (TR) are divided into two groups, $\alpha \beta$ and $\gamma \delta$, which express distinct TR containing either $\alpha$ and $\beta$, or $\gamma$ and $\delta$ chains, respectively. The TR$\alpha$ locus (TRA) and TR$\delta$ locus (TRD) of bovine (Bos taurus) and the sheep (Ovis aries) have recently been described and annotated by IMGT^® biocurators. The aim of the present study is to present the results of the biocuration and to compare the genes of the TRA/TRD loci among these ruminant species based on the Homo sapiens repertoire. The comparative analysis shows similarities but also differences, including the fact that these two species have a TRA/TRD locus about three times larger than that of humans and therefore have many more genes which may demonstrate duplications and/or deletions during evolution.

IMGT®, the international ImMunoGeneTics information system®, has advanced its comprehensive platform for the analysis of immunoglobulin (IG) and T-cell receptor (TR) genes through the development of new automated and scalable tools. This article presents major updates aligned with IMGT’s three axes of research. Axis I introduces dynamic resources such as IMGT/GeneTables, IMGT/AssemblyComparison, IMGT/CDRLengths, IMGT/MultiGenomeViewer, enabling real-time access to annotated genomic data, and IMGT/StatAssembly to assess quality of IG/TR loci in assemblies. Axis II enhances repertoire analysis with a redesigned IMGT/GeneFrequency tool and new customization features in IMGT/V-QUEST, supporting flexible exploration of IG and TR gene expression. Axis III improves the accurate prediction of peptide–MHC thanks to IMGT/RobustpMHC. Additionally, the IMGT knowledge graph and its therapeutic extension, IMGT/mAb-KG, provide semantically structured access to >100 million immunogenetic triplets, integrating IMGT databases and linking IMGT content to external biomedical resources. These developments promote standardization, interoperability, and integrative analysis across immunogenetics and clinical applications, reinforcing IMGT’s (accessible at https://www.imgt.org) role as a core reference in the era of FAIR data and personalized medicine.