3.3.4. Antibody Affinity

Nature of Affinity. The affinity with which antibody binds antigen results from a balance between the attractive and repulsive forces. A high affinity antibody impies a good fit and conversely, a low affinity antibody implies a poor fit (see Fig. 3.14).

Affinity Constant, Ka. All antigen-antibody reactions are reversible and the equilibrium constant K is called, the affinity constant (Fig. 3.15):

Ka ranges from 104 - 1012 liters/mole. Immunoglobulins with Ka < 104 for a particular antigen is ineffective.