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Immunoinformatics

IMGT®, the international ImMunoGeneTics information system®, was created in 1989 by Marie-Paule Lefranc at Montpellier, France (CNRS and University of Montpellier). The founding of IMGT® marked the advent of immunoinformatics, a new science, which emerged at the interface between immunogenetics and bioinformatics. 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 well as the conventional genes. This major breakthrough allowed genes and data of the complex and highly diversified adaptive immune responses to be managed in genomic databases and tools.

Immunoglobulins (IG)

Immunoglobulins (IG) or antibodies are antigen receptors of the B cells of the adaptive immune response, acquired by jawed vertebrates (or gnathostomata) more than 450 million years ago and found in all extant jawed vertebrate species from fishes to humans. IG are anchored in the membrane of a B cell as part of a signaling B cell receptor (BcR = membrane IG+CD79) or are secreted by plasmocytes. IG recognize antigens in their native (unprocessed) form. IG are made of two identical heavy (H) chains and two identical light (kappa or lambda) chains, encoded by genes located in three major loci: the IG heavy (IGH) locus at 14q32.33, IG kappa (IGK) locus at 2p11.2 and IG lambda (IGL) locus at 22q11.2. Genes outside of these major loci are orphons. There are four IG gene types, variable (V), diversity (D) (only for IGH), joining (J) and constant (C) genes which contribute to the IG chain synthesis. The variable domain at the N-terminal end of each IG chain results from a V-(D)-J rearrangement whereas the remaining of the chain, or constant region, is encoded by a C gene. The combinatorial and junctional diversity together with IG somatic hypermutations create a huge diversity of 1012 specific IG per individual, the limiting factor being only the number of B cells that an organism is genetically programmed to produce.

T cell receptors (TR)

T cell receptors (TR) are antigen receptors of the T cells of the adaptive immune response, acquired by jawed vertebrates (or gnathostomata) more than 450 million years ago and found in all extant jawed vertebrate species from fishes to humans. TR are anchored in the membrane of a T cell as part of the signaling T cell receptor (TcR = TR+CD3). TR alpha/beta recognize processed antigens, which are presented as peptides by the highly polymorphic major histocompatibility (MH, in humans HLA for human leukocyte antigens) proteins, whereas TR gamma/delta recognize nonpeptidic antigens. TR are made of two chains, alpha and beta, or gamma and delta, encoded by genes located in four major loci: the TR alpha (TRA) at 14q11.2, TR beta (TRB) at 7q34, TR gamma (TRG) at 7p14 and TR delta (TRD) at 14q11.2. Genes outside of these major loci are orphons. There are four TR gene types, variable (V), diversity (D) (for TRB and TRD), joining (J) and constant (C) genes which contribute to the TR chain synthesis. The variable domain at the N-terminal end of each TR chain results from a V-(D)-J rearrangement whereas the remaining of the chain, or constant region, is encoded by a C gene. The combinatorial and junctional diversity creates a huge potential diversity of 1012 specific TR per individual, the limiting factor being only the number of T cells that an organism is genetically programmed to produce.

Reference:
[1] Lefranc M-P. Immunoglobulin (IG) and T cell receptor genes (TR): IMGT® and the birth and rise of immunoinformatics. Front Immunol. 2014 Feb 05;5:22. doi: 10.3389/fimmu.2014.00022. Open access. PMID: 24600447
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