A measure of the binding constant of a single antigen -combining site with a monovalent antigenic determinant . The average affinity of a secreted antibody and of membrane Ig on antigen-specific B-cells increases following antigenic stimulation and is substantially higher in secondary than in primary antibody responses. This occurs due to small mutations in the DNA coding for IgV regions in individual antigen stimulated B lymphocytes. See also: Receptor

Specificity

The property of antibodies which enables them to react with some antigenic determinants and not with others. Specificity is dependent on chemical composition, physical forces, and molecular structure at the binding site.