Use of Radioisotopes in Immunochemical Research

Zusammenfassung

During the last few years isotopes have become one of the most important tools of the biochemists. Isotopically labeled molecules behave, in general, in the same manner as their unlabeled analogues. They allow us, however, to differentiate molecules formed after administration of the isotope from those formed before, and thus enable us to obtain more insight into the site and rate of formation of metabolites. Therefore, we may obtain information on the precursors of metabolites, their turn-over time and their breakdown products. For the same reason, isotopically labeled antigens have been used in immunochemical research. Tracing of isotopically labeled antigens has provided new information on their elimination from the circulation, their deposition in certain tissues or cells, their metabolic fate and their breakdown. In vitro experiments with labeled antigens allow us to measure their incorporation into antigen-antibody complexes. In animals injected with isotopically labeled amino acids, incorporation of these amino acids into antibody molecules can be measured. This enables us to determine the rate of antibody formation. Finally, experiments with isotopically labeled complement give some information on the components of the complement complex which combine with antigen-antibody aggregates. It is clear from this short survey that the application of isotopes enables us to investigate numerous problems which were inaccessible to experimental research prior to the availability of isotopes.

The experimental work described in this article has been supported by research grants from the National Science Foundation (G 5468) and the U.S. Public Health Service (C-1852), and by contracts of Indiana University with the Office of Naval Research (NR 108–035) and the Atomic Energy Commission [AT(11–1)209]. I am particularly grateful to Dr. Audrie N. Roberts for critical reading of the manuscript and for many helpful suggestions.