Affinity of Antigen–Antibody Interactions


Antibody affinity is the strength with which antibody binds to its target antigen. It is influenced by a variety of factors including valency and the precise fit of the antigen in the antigen binding groove. Antibody affinity increases over time following contact or repeated immunization with certain types of antigen. The affinity of an antibody may have an influence on its function.

Keywords: antibody; affinity; avidity; memory; somatic mutation

Figure 1.

Cartoon representation of an immunoglobulin molecule. The antibody combining site is determined by the variable (V) region genes of the heavy and light chain (dark and light blue respectively). The hypervariable regions (CDRs) and framework regions (FR) are indicated in a linear fashion. CDR3 is composed of rearranged VDJ (heavy) and VJ (light) chain genes. CDRs 1, 2 and 3 are the regions of the antibody molecule in greatest contact with antigen and form the three‐dimensional groove into which an epitope will fit. C = constant region.

Figure 2.

The intermolecular forces that are responsible for the binding of antibody to antigen. The strengths and the relative intermolecular distances over which the forces act differ. Hydrogen bonding is comparatively weak and can occur over relatively long distances while hydrophobic bonds are powerful but act over relatively short distances and thus require a ‘good fit’ of the antigen in the antibody binding site groove. The red arrow thickness represents the strength of the interaction, whilst the length of the respective black arrow relects the distance over which it acts.


Further Reading

Berek C (1993) Somatic mutation and memory. Current Opinion in Immunology 5: 218–222.

Goldberg ME and Djavadi‐Ohaniance L (1993) Methods for the measurement of antibody/antigen affinity based on ELISA and RIA. Current Opinion in Immunology 5: 278–281.

Goldblatt D, Pinto Vaz ARJPM and Miller E (1998) Antibody avidity as a surrogate marker of successful priming by Haemophilus influenzae type b conjugate vaccines following infant immunization. Journal of Infectious Diseases 177: 1112–1115.

Goldblatt D (1997) Simple solid phase assays of avidity. In: Turner MW and Johnstone AP (eds) Immunochemistry 2: A Practical Approach, pp. 31–51. Oxford: IRL Oxford University Press.

McHeyzer‐Williams MG and Ahmed R (1999) B cell memory and the long lived plasma cell. Current Opinion in Immunology 11: 172–179.

Nossal GJV (1992) The molecular and cellular basis of affinity maturation. Cell 68: 1–2.

Rada C, Gupta AK, Ghereardi and Milstein C (1991) Mutation and selection during the secondary response to 2‐phenyloxazolone. Proceedings of the National Academy of Sciences of the USA 88: 5508–5512.

Rajewsky K (1996) Clonal selection and learning in the antibody system. Nature 381: 751–758.

Tarlinton DM and Smith KG (2000) Dissecting affinity maturation: a model explaining selection of antibody‐forming cells and memory B cells in the germinal centre. Immunology Today 21: 436–441.

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Goldblatt, David(Apr 2001) Affinity of Antigen–Antibody Interactions. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1038/npg.els.0001113]