13039 IUPAC Gold Book - constant region 10.1351/goldbook.13039 13039 current synonyms: C region, constant (C) region 1 Part of an immunoglobulin (Ig) or T-cell receptor (TCR) that is relatively constant in amino acid sequence among different Ig or TCR molecules. In an antibody molecule the constant regions of each chain are composed of up to four C domains. The constant region of an antibody determines its general type of interaction. T-cell receptor (TCR) https://goldbook.iupac.org//terms/view/13714 variable (V) region https://goldbook.iupac.org//terms/view/13773 PAC, 2012, 84, 1113. 'IUPAC glossary of terms used in immunotoxicology (IUPAC Recommendations 2012)' on page 1148 (https://doi.org/10.1351/PAC-REC-11-06-03) https://goldbook.iupac.org/terms/view/13039/html https://goldbook.iupac.org/terms/view/13039/json https://goldbook.iupac.org/terms/view/13039/plain Citation: 'constant region' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351/goldbook.13039 The IUPAC Gold Book is licensed under Creative Commons Attribution-ShareAlike CC BY-SA 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) for individual terms. If you are interested in licensing the Gold Book for commercial use, please contact the IUPAC Executive Director at executivedirector@iupac.org . The International Union of Pure and Applied Chemistry (IUPAC) is continuously reviewing and, where needed, updating terms in the Compendium of Chemical Terminology (the IUPAC Gold Book). Users of these terms are encouraged to include the version of a term with its use and to check regularly for updates to term definitions that you are using. 2026-07-14T05:29:28+00:00