The molecular synthesis and genetics of the immunoglobulin (IG) and T-cell-receptor (TR) chains are particularly complex and unique, as they include biological mechanisms such as DNA molecular rearrangements in multiple loci (three for IG and four for TR in human) located on different chromosomes (four in human), nucleotide deletions and insertions at the rearrangement junctions (or N-diversity), and somatic hypermutations in the IG loci (for review, see refs. 1,2). The number of potential protein forms of IG and TR is almost unlimited. Because of the complexity and large number of published sequences, data control and classification and detailed annotations are a very difficult task for the general databanks such as EMBL, GenBank, and DDBJ (3–5). These observations were the starting point of IMGT, the International ImMunoGeneTics Information System® ( http://imgt.cines.fr ) (6), created in 1989 by the Laboratoire ďImmunoGénétique Moléculaire (LIGM), at the Université Montpellier II, CNRS, Montpellier, France.