Reactivity per unit weight: an important parameter in the quality assurance of antibody reagents for vaccine analysis

The common practice of characterizing antibody reagents by "titre" leaves hidden pitfalls that make accurate immunoassays difficult to achieve. With an affinity purified antibody, it becomes possible to define antibody reagents by reactivity per unit weight of antibody. The antibody reagents for the analysis of the heterogenous antibody response to a vaccine need broad-spectrum reactivity of appropriate specificity. If antibody reagents are characterized by their reactivity per unit weight to a range of appropriate antigens, it becomes possible to detect and avoid pitfalls that otherwise contribute to huge variations and uninterpretable results. Reactivity per unit weight is especially important for the characterization of enzyme conjugates of antibodies. Although absolute reactivity per unit weight is difficult to define, it is easy to determine the relative reactivity of two antibody preparations. Examples illustrate the importance of reactivity per unit weight.