Antibody quantitation in human and veterinary medicine

The determination of antibodies is a matter of clinical importance since it may prove or disprove the existence of an immune reaction against a specific foreign or autologous antigen. It is useful to monitor the immune response against a vaccine or the disappearance of injected therapeutic antibodies and in fundamental immunological research or in industrial R & D. However, this determination of this particular analyte cannot end up with a significant mass measurement, as a result of the heterogeneity of the antibodies present in most samples (with the exception of monoclonal antibody research). This heterogeneity has multiple facets concerning the constant region (isotypes) and the variable region (degeneracy of the antibody response). What is measured is a binding activity of the antibodies for the corresponding antigen. Calibration is a challenge impossible to carry out. In all cases, the selection of an antibody calibrator results from a compromise. The expression of the results can be done in a variety of ways, and presently is far from being standardized. The present state of the art is characterized by the absence of reference method, the scarcity of reference preparation both for antibody and antigen and the lack of comparability of the methods. Improvement can be expected from the better knowledge of antigens and of their epitopes, the selection and the preparation of pure antigen molecule or synthetic molecules. There are a few technical possibilities to approach a better standardization. Finally, the results of such standardized methods should be interpreted operationally, without reference to ponderal estimations, for a specific clinical or epidemiological purpose. Each method should be validated by epidemiological studies.