Antibody V and C domain sequence, structure, and interaction analysis with special reference to IMGT®

Recent advances in bioreceptor-based sensing for extracellular vesicle analysis

Extracellular vesicles (EVs) are nanoscale, membrane-bound structures secreted by various cell types into biofluids. They show great potential as biomarkers for disease diagnostics, owing to their ability to carry molecular cargo that reflects their cellular origin. However, the inherent heterogeneity of EVs in terms of size, composition, and source presents significant challenges for reliable detection and analysis. Recent advances in bioreceptor-based biosensor technologies provide promising solutions by offering high sensitivity and specificity in EV detection and characterization. These technologies address the limitations of conventional methods, such as ultracentrifugation and bulk analysis. Biosensors utilizing antibodies, aptamers, peptides, lectins, and molecularly imprinted polymers enable precise detection of EV subpopulations by targeting specific EV surface markers, including proteins, lipids, and glycans. Additionally, these biosensors support multiplexed and real-time analysis while preserving the structural integrity of EVs. This review highlights the transformative potential of combining modern biosensing tools with bioreceptor technologies to advance EV research and diagnostics, paving the way for innovations in disease diagnostics and therapeutic monitoring.

Using IMGT unique numbering for IG allotypes and Fc-engineered variants of effector properties and half-life of therapeutic antibodies

Therapeutic monoclonal antibodies (mAb) are usually of the IgG1, IgG2, and IgG4 classes, and their heavy chains may be modified by amino acid (aa) changes involved in antibody-dependent cellular cytotoxicity (ADCC), antibody-dependent cellular phagocytosis (ADCP), complement-dependent cytotoxicity (CDC), and/or half-life. Allotypes and Fc-engineered variants are classified using IMGT/HGNC gene nomenclature (e.g., Homo sapiens IGHG1). Allotype names follow the WHO/IMGT nomenclature. IMGT-engineered variant names use the IMGT nomenclature (e.g., Homsap G1v1), which comprises species and gene name (both abbreviated) followed by the letter v (for variant) and a number. Both allotypes and engineered variants are defined by their aa changes and positions, based on the IMGT unique numbering for C domain, identified in sequence motifs, referred to as IMGT topological motifs, as their limits and length are standardized and correspond to a structural feature (e.g., strand or loop). One hundred twenty-six variants are displayed with their type, IMGT numbering, Eu-IMGT positions, motifs before and after changes, and their property and function (effector and half-life). Three motifs characterize effector variants, CH2 1.6-3, 23-BC-41, and the FG loop, whereas three different motifs characterize half-life variants, two on CH2 13-AB-18 and 89-96 with H93, and one on CH3 the FG loop with H115.

BCR, not TCR, repertoire diversity is associated with favorable COVID-19 prognosis

Introduction

The SARS-CoV-2 pandemic has had a widespread and severe impact on society, yet there have also been instances of remarkable recovery, even in critically ill patients.

Materials and methods

In this study, we used single-cell RNA sequencing to analyze the immune responses in recovered and deceased COVID-19 patients during moderate and critical stages.

Results

Expanded T cell receptor (TCR) clones were predominantly SARS-CoV-2-specific, but represented only a small fraction of the total repertoire in all patients. In contrast, while deceased patients exhibited monoclonal B cell receptor (BCR) expansions without COVID-19 specificity, survivors demonstrated diverse and specific BCR clones. These findings suggest that neither TCR diversity nor BCR monoclonal expansions are sufficient for viral clearance and subsequent recovery. Differential gene expression analysis revealed that protein biosynthetic processes were enriched in survivors, but that potentially damaging mitochondrial ATP metabolism was activated in the deceased.

Conclusion

This study underscores that BCR repertoire diversity, but not TCR diversity, correlates with favorable outcomes in COVID-19.

Antibody Sequence and Structure Analyses Using IMGT®: 30 Years of Immunoinformatics

IMGT^®, the international ImMunoGeneTics information system^®, http://www.imgt.org , the global reference in immunogenetics and immunoinformatics, was created in 1989 by Marie-Paule Lefranc (Université de Montpellier and CNRS) to manage the huge diversity of the antigen receptors, immunoglobulins (IG) or antibodies, and T cell receptors (TR) of the adaptive immune responses. The founding of IMGT^® marked the advent of immunoinformatics, which emerged at the interface between immunogenetics and bioinformatics. IMGT^® standardized analysis of the IG, TR, and major histocompatibility (MH) genes and proteins bridges the gap between sequences and three-dimensional (3D) structures, for all jawed vertebrates from fish to humans. This is achieved through the IMGT Scientific chart rules, based on the IMGT-ONTOLOGY axioms, and primarily CLASSIFICATION (IMGT gene and allele nomenclature) and NUMEROTATION (IMGT unique numbering and IMGT Colliers de Perles). IMGT^® comprises seven databases (IMGT/LIGM-DB for nucleotide sequences, IMGT/GENE-DB for genes and alleles, etc.), 17 tools (IMGT/V-QUEST, IMGT/JunctionAnalysis, IMGT/HighV-QUEST for NGS, etc.), and more than 20,000 Web resources. In this chapter, the focus is on the tools for amino acid sequences per domain (IMGT/DomainGapAlign and IMGT/Collier-de-Perles), and on the databases for receptors (IMGT/2Dstructure-DB and IMGT/3D-structure-DB) described per receptor, chain, and domain and, for 3D, with contact analysis, paratope, and epitope. The IMGT/mAb-DB is the query interface for monoclonal antibodies (mAb), fusion proteins for immune applications (FPIA), composite proteins for clinical applications (CPCA), and related proteins of interest (RPI) with links to IMGT^® 2D and 3D databases and to the World Health Organization (WHO) International Nonproprietary Names (INN) program lists. The chapter includes the human IG allotypes and antibody engineered variants for effector properties used in the description of therapeutical mAb.

IMGT ® Nomenclature of Engineered IGHG Variants Involved in Antibody Effector Properties and Formats

The constant region of the immunoglobulin (IG) or antibody heavy gamma chain is frequently engineered to modify the effector properties of the therapeutic monoclonal antibodies. These variants are classified in regards to their effects on effector functions, antibody-dependent cytotoxicity (ADCC), antibody-dependent phagocytosis (ADCP), complement-dependent cytotoxicity (CDC) enhancement or reduction, B cell inhibition by the coengagement of antigen and FcγR on the same cell, on half-life increase, and/or on structure such as prevention of IgG4 half-IG exchange, hexamerisation, knobs-into-holes and the heteropairing H-H of bispecific antibodies, absence of disulfide bridge inter H-L, absence of glycosylation site, and site-specific drug attachment engineered cysteine. The IMGT engineered variant identifier is comprised of the species and gene name (and eventually allele), the letter 'v' followed by a number (assigned chronologically), and for each concerned domain (e.g, CH1, h, CH2 and CH3), the novel AA (single letter abbreviation) and IMGT position according to the IMGT unique numbering for the C-domain and between parentheses, the Eu numbering. IMGT engineered variants are described with detailed amino acid changes, visualized in motifs based on the IMGT numbering bridging genes, sequences, and structures for higher order description.

A cell-based screening method using an intracellular antibody for discovering small molecules targeting the translocation protein LMO2

Intracellular antibodies are tools that can be used directly for target validation by interfering with properties like protein-protein interactions. An alternative use of intracellular antibodies in drug discovery is developing small-molecule surrogates using antibody-derived (Abd) technology. We previously used this strategy with an in vitro competitive surface plasmon resonance method that relied on high-affinity antibody fragments to obtain RAS-binding compounds. We now describe a novel implementation of the Abd method with a cell-based intracellular antibody-guided screening method that we have applied to the chromosomal translocation protein LMO2. We have identified a chemical series of anti-LMO2 Abd compounds that bind at the same LMO2 location as the inhibitory anti-LMO2 intracellular antibody combining site. Intracellular antibodies could therefore be used in cell-based screens to identify chemical surrogates of their binding sites and potentially be applied to any challenging proteins, such as transcription factors that have been considered undruggable.

Immunoglobulins or Antibodies: IMGT® Bridging Genes, Structures and Functions

IMGT®, the international ImMunoGeneTics® information system founded in 1989 by Marie-Paule Lefranc (Université de Montpellier and CNRS), marked the advent of immunoinformatics, a new science at the interface between immunogenetics and bioinformatics. For the first time, the immunoglobulin (IG) or antibody and T cell receptor (TR) genes were officially recognized as 'genes' as well as were conventional genes. This major breakthrough has allowed the entry, in genomic databases, of the IG and TR variable (V), diversity (D) and joining (J) genes and alleles of Homo sapiens and of other jawed vertebrate species, based on the CLASSIFICATION axiom. The second major breakthrough has been the IMGT unique numbering and the IMGT Collier de Perles for the V and constant (C) domains of the IG and TR and other proteins of the IG superfamily (IgSF), based on the NUMEROTATION axiom. IMGT-ONTOLOGY axioms and concepts bridge genes, sequences, structures and functions, between biological and computational spheres in the IMGT® system (Web resources, databases and tools). They provide the IMGT Scientific chart rules to identify, to describe and to analyse the IG complex molecular data, the huge diversity of repertoires, the genetic (alleles, allotypes, CNV) polymorphisms, the IG dual function (paratope/epitope, effector properties), the antibody humanization and engineering.

A comparison of immunoglobulin IGHV, IGHD and IGHJ genes in wild-derived and classical inbred mouse strains

The genomes of classical inbred mouse strains include genes derived from all three major subspecies of the house mouse, Mus musculus. We recently posited that genetic diversity in the immunoglobulin heavy chain (IGH) gene loci of C57BL/6 and BALB/c mice reflects differences in subspecies origin. To investigate this hypothesis, we conducted high-throughput sequencing of IGH gene rearrangements to document IGH variable (IGHV), joining (IGHJ) and diversity (IGHD) genes in four inbred wild-derived mouse strains (CAST/EiJ, LEWES/EiJ, MSM/MsJ and PWD/PhJ) and a single disease model strain (NOD/ShiLtJ), collectively representing genetic backgrounds of several major mouse subspecies. A total of 341 germline IGHV sequences were inferred in the wild-derived strains, including 247 not curated in the international ImMunoGeneTics information system. By contrast, 83/84 inferred NOD IGHV genes had previously been observed in C57BL/6 mice. Variability among the strains examined was observed for only a single IGHJ gene, involving a description of a novel allele. By contrast, unexpected variation was found in the IGHD gene loci, with four previously unreported IGHD gene sequences being documented. Very few IGHV sequences of C57BL/6 and BALB/c mice were shared with strains representing major subspecies, suggesting that their IGH loci may be complex mosaics of genes of disparate origins. This suggests a similar level of diversity is likely present in the IGH loci of other classical inbred strains. This must now be documented if we are to properly understand interstrain variation in models of antibody-mediated disease.

IMGT® and 30 Years of Immunoinformatics Insight in Antibody V and C Domain Structure and Function

At the 10th Human Genome Mapping (HGM10) Workshop, in New Haven, for the first time, immunoglobulin (IG) or antibody and T cell receptor (TR) variable (V), diversity (D), joining (J), and constant (C) genes were officially recognized as 'genes', as were the conventional genes. Under these HGM auspices, IMGT®, the international ImMunoGeneTics information system®, was created in June 1989 at Montpellier (University of Montpellier and CNRS). The creation of IMGT® marked the birth of immunoinformatics, a new science, at the interface between immunogenetics and bioinformatics. The accuracy and the consistency between genes and alleles, sequences, and three-dimensional (3D) structures are based on the IMGT Scientific chart rules generated from the IMGT-ONTOLOGY axioms and concepts: IMGT standardized keywords (IDENTIFICATION), IMGT gene and allele nomenclature (CLASSIFICATION), IMGT standardized labels (DESCRIPTION), IMGT unique numbering and IMGT Collier de Perles (NUMEROTATION). These concepts provide IMGT® immunoinformatics insights for antibody V and C domain structure and function, used for the standardized description in IMGT® web resources, databases and tools, immune repertoires analysis, single cell and/or high-throughput sequencing (HTS, NGS), antibody humanization, and antibody engineering in relation with effector properties.

Unbiased quantification of immunoglobulin diversity at the DNA level with VDJ-seq

For high-throughput sequencing and quantification of immunoglobulin repertoires, most methodologies use RNA. However, output varies enormously between recombined genes due to different promoter strengths and differential activation of lymphocyte subsets, precluding quantitation of recombinants on a per-cell basis. To date, DNA-based approaches have used V gene primer cocktails, with substantial inherent biases. Here, we describe VDJ sequencing (VDJ-seq), which accurately quantitates immunoglobulin diversity at the DNA level in an unbiased manner. This is accomplished with a single primer-extension step using biotinylated J gene primers. By addition of unique molecular identifiers (UMIs) before primer extension, we reliably remove duplicate sequences and correct for sequencing and PCR errors. Furthermore, VDJ-seq captures productive and nonproductive VDJ and DJ recombination events on a per-cell basis. Library preparation takes 3 d, with 2 d of sequencing and 1 d of data processing and analysis.

Use of IMGT® Databases and Tools for Antibody Engineering and Humanization

IMGT^®, the international ImMunoGeneTics information system^® ( http://www.imgt.org ), was created in 1989 by Marie-Paule Lefranc (Université de Montpellier and CNRS) to manage the huge diversity of the antigen receptors, immunoglobulins (IG) or antibodies, and T cell receptors (TR). The founding of IMGT^® marked the advent of immunoinformatics, which emerged at the interface between immunogenetics and bioinformatics. Standardized sequence and structure analysis of antibody using IMGT^® databases and tools allow one to bridge, for the first time, the gap between antibody sequences and three-dimensional (3D) structures. This is achieved through the IMGT Scientific chart rules, based on the IMGT-ONTOLOGY concepts of classification (IMGT gene and allele nomenclature), description (IMGT standardized labels), and numerotation (IMGT unique numbering and IMGT Collier de Perles). IMGT^® is acknowledged as the global reference for immunogenetics and immunoinformatics, and its standards are particularly useful for antibody engineering and humanization. IMGT^® databases for antibody nucleotide sequences and genes include IMGT/LIGM-DB and IMGT/GENE-DB, respectively, and nucleotide sequence analysis is performed by the IMGT/V-QUEST and IMGT/JunctionAnalysis tools and for NGS by IMGT/HighV-QUEST. In this chapter, we focus on IMGT^® databases and tools for amino acid sequences, two-dimensional (2D) and three-dimensional (3D) structures: the IMGT/DomainGapAlign and IMGT Collier de Perles tools and the IMGT/2Dstructure-DB and IMGT/3Dstructure-DB database. IMGT/mAb-DB provides the query interface for monoclonal antibodies (mAb), fusion proteins for immune applications (FPIA), and composite proteins for clinical applications (CPCA) and related proteins of interest (RPI) and links to the proposed and recommended lists of the World Health Organization International Nonproprietary Name (WHO INN) programme, to IMGT/2Dstructure-DB for amino acid sequences, and to IMGT/3Dstructure-DB and its associated tools (IMGT/StructuralQuery, IMGT/DomainSuperimpose) for crystallized antibodies.

IG and TR single chain fragment variable (scFv) sequence analysis: a new advanced functionality of IMGT/V-QUEST and IMGT/HighV-QUEST

BACKGROUND

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.

METHODS

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.

RESULTS

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.

CONCLUSION

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.

Early Emergence of CD19-Negative Human Antibody-Secreting Cells at the Plasmablast to Plasma Cell Transition

Long-lived human plasma cells (PCs) play central roles in immunity and autoimmunity and are enriched among the subpopulation of CD19neg human PCs. However, whether human CD19neg PCs are necessarily aged cells that have gradually lost CD19 expression is not known. Assessing peripheral blood samples at steady-state and during the acute response to influenza vaccination in healthy donors, we identify the presence of phenotypic CD19neg plasmablasts, the proliferative precursor state to mature PCs, and demonstrate by ELISPOT that these are Ab-secreting cells (ASCs). During the acute response to influenza vaccination, CD19pos, CD19low, and CD19neg ASCs secrete vaccine-specific Abs and show linked IGHV repertoires. To address precursor/product relationships, we use in vitro models that mimic T-dependent and T-independent differentiation, finding that the CD19neg state can be established at the plasmablast to PC transition, that CD19neg PCs increase as a percentage of surviving PCs in vitro, and that CD19neg and CD19pos PCs can be maintained independently. These data provide proof-of-principle for the view that newly generated ASCs can acquire a mature PC phenotype that is accompanied by loss of CD19 expression at an early stage of differentiation and that aging is not an obligate requirement for a CD19neg state to be established.

Antibody Aggregation: Insights from Sequence and Structure

Monoclonal antibodies (mAbs) are the fastest-growing biological therapeutics with important applications ranging from cancers, autoimmunity diseases and metabolic disorders to emerging infectious diseases. Aggregation of mAbs continues to be a major problem in their developability. Antibody aggregation could be triggered by partial unfolding of its domains, leading to monomer-monomer association followed by nucleation and growth. Although the aggregation propensities of antibodies and antibody-based proteins can be affected by the external experimental conditions, they are strongly dependent on the intrinsic antibody properties as determined by their sequences and structures. In this review, we describe how the unfolding and aggregation susceptibilities of IgG could be related to their cognate sequences and structures. The impact of antibody domain structures on thermostability and aggregation propensities, and effective strategies to reduce aggregation are discussed. Finally, the aggregation of antibody-drug conjugates (ADCs) as related to their sequence/structure, linker payload, conjugation chemistry and drug-antibody ratio (DAR) is reviewed.

IMGT®, the international ImMunoGeneTics information system® 25 years on

IMGT(®), the international ImMunoGeneTics information system(®)(http://www.imgt.org) is the global reference in immunogenetics and immunoinformatics. By its creation in 1989 by Marie-Paule Lefranc (Université de Montpellier and CNRS), IMGT(®) marked the advent of immunoinformatics, which emerged at the interface between immunogenetics and bioinformatics. IMGT(®) is specialized in the immunoglobulins (IG) or antibodies, T cell receptors (TR), major histocompatibility (MH) and proteins of the IgSF and MhSF superfamilies. IMGT(®) is built on the IMGT-ONTOLOGY axioms and concepts, which bridged the gap between genes, sequences and 3D structures. The concepts include the IMGT(®) standardized keywords (identification), IMGT(®) standardized labels (description), IMGT(®) standardized nomenclature (classification), IMGT unique numbering and IMGT Colliers de Perles (numerotation). IMGT(®) comprises 7 databases, 17 online tools and 15,000 pages of web resources, and provides a high-quality and integrated system for analysis of the genomic and expressed IG and TR repertoire of the adaptive immune responses, including NGS high-throughput data. Tools and databases are used in basic, veterinary and medical research, in clinical applications (mutation analysis in leukemia and lymphoma) and in antibody engineering and humanization. The IMGT/mAb-DB interface was developed for therapeutic antibodies and fusion proteins for immunological applications (FPIA). IMGT(®) is freely available at http://www.imgt.org.

Immunoglobulins: 25 years of immunoinformatics and IMGT-ONTOLOGY

IMGT®, the international ImMunoGeneTics information system® (CNRS and Montpellier University) is the global reference in immunogenetics and immunoinformatics. By its creation in 1989, IMGT® marked the advent of immunoinformatics, which emerged at the interface between immunogenetics and bioinformatics. IMGT® is specialized in the immunoglobulins (IG) or antibodies, T cell receptors (TR), major histocompatibility (MH), and IgSF and MhSF superfamilies. IMGT® has been built on the IMGT-ONTOLOGY axioms and concepts, which bridged the gap between genes, sequences and three-dimensional (3D) structures. The concepts include the IMGT® standardized keywords (identification), IMGT® standardized labels (description), IMGT® standardized nomenclature (classification), IMGT unique numbering and IMGT Colliers de Perles (numerotation). IMGT® comprises seven databases, 15,000 pages of web resources and 17 tools. IMGT® tools and databases provide a high-quality analysis of the IG from fish to humans, for basic, veterinary and medical research, and for antibody engineering and humanization. They include, as examples: IMGT/V-QUEST and IMGT/JunctionAnalysis for nucleotide sequence analysis and their high-throughput version IMGT/HighV-QUEST for next generation sequencing, IMGT/DomainGapAlign for amino acid sequence analysis of IG domains, IMGT/3Dstructure-DB for 3D structures, contact analysis and paratope/epitope interactions of IG/antigen complexes, and the IMGT/mAb-DB interface for therapeutic antibodies and fusion proteins for immunological applications (FPIA).

Engineered Fc based antibody domains and fragments as novel scaffolds

Therapeutic monoclonal antibodies (mAbs) have been successful for the therapy of a number of diseases mostly cancer and immune disorders. However, the vast majority of mAbs approved for clinical use are full size, typically in IgG1 format. These mAbs may exhibit relatively poor tissue penetration and restricted epitope access due to their large size. A promising solution to this fundamental limitation is the engineering of smaller scaffolds based on the IgG1 Fc region. These scaffolds can be used for the generation of libraries of mutants from which high-affinity binders can be selected. Comprised of the CH2 and CH3 domains, the Fc region is important not only for the antibody effector function but also for its long half-life. This review focuses on engineered Fc based antibody fragments and domains including native (dimeric) Fc and monomeric Fc as well as CH2 and monomeric CH3, and their use as novel scaffolds and binders. The Fc based binders are promising candidate therapeutics with optimized half-life, enhanced tissue penetration and access to sterically restricted binding sites resulting in an increased therapeutic efficacy. This article is part of a Special Issue entitled: Recent advances in molecular engineering of antibody.

Immunoglobulin and T Cell Receptor Genes: IMGT(®) and the Birth and Rise of Immunoinformatics

IMGT(®), the international ImMunoGeneTics information system(®) (1), (CNRS and Université Montpellier 2) is the global reference in immunogenetics and immunoinformatics. By its creation in 1989, IMGT(®) marked the advent of immunoinformatics, which emerged at the interface between immunogenetics and bioinformatics. IMGT(®) is specialized in the immunoglobulins (IG) or antibodies, T cell receptors (TR), major histocompatibility (MH), and proteins of the IgSF and MhSF superfamilies. IMGT(®) has been built on the IMGT-ONTOLOGY axioms and concepts, which bridged the gap between genes, sequences, and three-dimensional (3D) structures. The concepts include the IMGT(®) standardized keywords (concepts of identification), IMGT(®) standardized labels (concepts of description), IMGT(®) standardized nomenclature (concepts of classification), IMGT unique numbering, and IMGT Colliers de Perles (concepts of numerotation). IMGT(®) comprises seven databases, 15,000 pages of web resources, and 17 tools, and provides a high-quality and integrated system for the analysis of the genomic and expressed IG and TR repertoire of the adaptive immune responses. Tools and databases are used in basic, veterinary, and medical research, in clinical applications (mutation analysis in leukemia and lymphoma) and in antibody engineering and humanization. They include, for example IMGT/V-QUEST and IMGT/JunctionAnalysis for nucleotide sequence analysis and their high-throughput version IMGT/HighV-QUEST for next-generation sequencing (500,000 sequences per batch), IMGT/DomainGapAlign for amino acid sequence analysis of IG and TR variable and constant domains and of MH groove domains, IMGT/3Dstructure-DB for 3D structures, contact analysis and paratope/epitope interactions of IG/antigen and TR/peptide-MH complexes and IMGT/mAb-DB interface for therapeutic antibodies and fusion proteins for immune applications (FPIA).