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Definition

noun, plural: avidities

The combined strength of bond affinities in a complex.

Usage

The term may be used in chemistry to describe the dissociation-dependent strength of an acid or base. In proteins, avidity describes the binding intensity of multiple bond interactions between proteins.

In immunology, avidity refers to the strength of antibody-antigen binding. In this regard, avidity may be different from affinity. The latter being a term used to describe the strength of a particular bond, i.e. the affinity of an antibody for the antigen as the strength of a non-covalent association between an antigen-binding site with a single antigenic epitope¹. For instance, IgM may have low affinity but it has high avidity due to its 10 weak binding sites contrary to the two strong binding sites of IgG.

Miscellaneous

Compare: affinity See also: antibody-antigen complex, protein

Reference: ¹Mak, Tak W. and Mary E. Saunders. Primer to the Immune Response. Amsterdam: Academic/Elsevier, 2008. 74.