The 'entity' concept describes the conformation of an IG or a TR sequence. This concept of DESCRIPTION takes into account the three following concepts of IDENTIFICATION and their instances:
- - gene type: variable (V), diversity (D), joining (J) and constant (C)
- - molecule type: genomic DNA, cDNA and protein
- - configuration: germline, rearranged (for V, D and J genes) and not defined (for C gene)
Fourteen instances of the 'entity' concept have been defined so far to cover all cases of IG and TR sequence conformation: V-GENE, D-GENE, J-GENE, C-GENE, V-J-GENE, V-D-J-GENE, D-J-GENE, L-V-SEQUENCE, D-SEQUENCE, J-SEQUENCE, J-C-SEQUENCE, C-SEQUENCE, L-V-J-C-SEQUENCE, L-V-D-J-C-SEQUENCE.
For examples, the instance V-GENE represents a genomic V gene in germline configuration, whereas the instance V-J-GENE represents genomic V and J genes in rearranged configuration.
These different instances are linked to each other by relations that reflect the steps of the IG and TR chain synthesis: "is rearranged into" and "is transcribed into".
The 'entity' concept is part of the 'DESCRIPTION' concept of IMGT-ONTOLOGY
 Giudicelli, V. and Lefranc, M.-P., Bioinformatics, 15, 1047-1054 (1999) PMID: 10745995, LIGM:221