Final answer:
Equilibrium dialysis is used to measure the affinity of an antibody, which is the strength of the binding between a single antibody site and an antigen's epitope. Affinity is one aspect of how strongly and stably an antibody can bind to its specific antigen, differentiating from avidity, which involves multiple binding interactions.
Step-by-step explanation:
The characteristic of a specific antibody that is measured by equilibrium dialysis is affinity. Affinity is the measure of the binding strength between a single antibody binding site and an antigen's epitope. The higher the affinity, the stronger and more stable the binding between the antibody and antigen. In contrast, avidity refers to the overall binding strength when multiple antibody interactions occur simultaneously, such as with polyvalent antibodies like IgM and IgA, which can bind to several antigens at once. Avidity is influenced by affinity and also depends on how the antibody and antigen are arranged structurally.
It is important to note that cross-reactivity more likely occurs with antibodies and antigens that have a low affinity or avidity. In these cases, an antibody may bind to an antigen that is chemically similar to the intended target antigen, which can affect the antibody's specificity. Monoclonal antibodies provide higher specificity and typically have high affinity to a single epitope on an antigen, which makes them a powerful tool in research and medical diagnostics.