antigen-antibody reaction
the reversible binding of antigen to homologous antibody brought about by the formation of weak bonds between antigenic determinants on antigen molecules and antigen binding sites on immunoglobulin molecules. Certain effects, e.g., precipitation and agglutination reactions and viral neutralization, result from the binding itself; other effects, e.g., complement activation and opsonization, result from conformational changes that occur in immunoglobulin molecules with antigen binding and enable them to interact with complement proteins and Fc receptors on phagocytes.
Medical dictionary.
2011.