Complementarity-Determining Regions (CDRs)
Definition
Six hypervariable loops, three in the heavy-chain variable domain and three in the light-chain variable domain, that together form the antigen-binding site. Their amino-acid sequence determines which epitope the antibody recognises with high specificity.
- Abbreviation
- CDRs
- Count
- Six loops (three heavy chain, three light chain)
- Location
- Variable domains of the antibody
- Function
- Form the antigen-binding site
Common questions
Why are CDRs described as hypervariable?+
Their amino-acid sequence varies far more between different antibodies than the surrounding framework regions of the variable domain, because this variability is what generates the enormous diversity of antigens the immune system can recognise, with each antibody clone carrying its own distinct CDR sequences.
Which CDR usually contributes most to antigen specificity?+
CDR3 of the heavy chain is generally considered the most variable and the largest single contributor to antigen-binding specificity among the six loops, since it is generated by additional recombination and junctional diversity not present in the other CDRs.
Related terms
- Affinity
- The binding strength of a single antigen-binding site for one epitope, expressed as the equilibrium dissociation constant (Kd). A lower Kd indicates...
- Cross-Reactivity
- The capacity of an antibody raised against one analyte to bind structurally related compounds. In RIA, cross-reactivity is the main driver of...
- Fab Fragment
- The antigen-binding fragment of an antibody, consisting of one complete light chain paired with the variable and first constant domain of a...
- Fc Region
- The crystallisable fragment of an antibody, formed by the paired constant domains of the two heavy chains. The Fc region mediates effector...
- Monoclonal Antibody (mAb)
- An antibody produced by a single hybridoma clone, so that every molecule in the preparation is identical, targets the same epitope, and...