Title: constant region
Long Title: IUPAC Gold Book - constant region
DOI: 10.1351/goldbook.13039
Status: current

Definition
Part of an immunoglobulin (Ig) or T-cell receptor (TCR) that is relatively constant in amino acid sequence among different Ig or TCR molecules.

Note
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.

Related Terms
- T-cell receptor (TCR): https://goldbook.iupac.org/terms/view/13714
- variable (V) region: https://goldbook.iupac.org/terms/view/13773

Source
- 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)

Other Outputs
- html: https://goldbook.iupac.org/terms/view/13039/html
- json: https://goldbook.iupac.org/terms/view/13039/json
- xml: https://goldbook.iupac.org/terms/view/13039/xml

Citation: 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
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Accessed: 2026-05-10T19:15:02+00:00