What term describes the binding strength of an antibody for an antigen?

The term that describes the binding strength of an antibody for an antigen is "affinity." Affinity refers to the strength of the interaction between a single antibody binding site and its corresponding antigenic determinant. This interaction is typically characterized by the equilibrium constant for the reaction, indicating how tightly the antibody binds to the antigen.

Avidity is often confused with affinity, but it represents the overall strength of binding of an antibody to an antigen when multiple binding sites are involved, such as in the case of multivalent antibodies binding to multivalent antigens. In contrast, affinity pertains to the binding strength of a single site, making it the more precise term for describing the specific interaction between an antibody and a single antigen epitope.

Elegance and potency do not pertain to the measurement of binding strength in this context. Elegance is not a recognized term in immunology regarding antibody-antigen interactions, and potency typically refers to the biological activity or effectiveness of a substance at a given concentration, rather than the binding characteristics of antibodies.

Understanding the distinction between affinity and avidity is crucial in immunology, as it helps clarify interactions in various immunological responses and therapeutic applications.