Which term describes the overall strength of binding when multiple antigen–antibody interactions occur between an antibody and a multivalent antigen?

Which term describes the overall strength of binding when multiple antigen–antibody interactions occur between an antibody and a multivalent antigen?

• A. Affinity
• B. Avidity
• C. Van der Waals attraction
• D. Covalence

Answer: (B)

When multiple contact points form between an antibody and a multivalent antigen, the overall binding strength is described by avidity. Avidity captures the combined strength of all antigen–antibody interactions together, not just a single binding site. If an antibody has several binding sites engaging multiple epitopes, the complex is held together more tightly and dissociates more slowly than any one individual interaction would suggest. This is especially true for antibodies with many binding sites, like IgM, which can have ten simultaneous contacts, leading to very high avidity even if each site binds moderately. By contrast, affinity refers to the strength of a single antigen–antibody contact at one binding site and is a property of that individual interaction, not the whole multivalent complex. The other terms aren’t the measuring concept here: van der Waals attraction is one type of weak interaction involved in binding but does not quantify the overall binding strength of a multivalent complex, and covalence implies covalent bonds, which are not the typical reversible interactions in antigen–antibody binding.

When multiple contact points form between an antibody and a multivalent antigen, the overall binding strength is described by avidity. Avidity captures the combined strength of all antigen–antibody interactions together, not just a single binding site. If an antibody has several binding sites engaging multiple epitopes, the complex is held together more tightly and dissociates more slowly than any one individual interaction would suggest. This is especially true for antibodies with many binding sites, like IgM, which can have ten simultaneous contacts, leading to very high avidity even if each site binds moderately.

By contrast, affinity refers to the strength of a single antigen–antibody contact at one binding site and is a property of that individual interaction, not the whole multivalent complex. The other terms aren’t the measuring concept here: van der Waals attraction is one type of weak interaction involved in binding but does not quantify the overall binding strength of a multivalent complex, and covalence implies covalent bonds, which are not the typical reversible interactions in antigen–antibody binding.