Radiolabelling of Antibodies: Methods and Limitations^[*]

The development of a labelled antibody for radioimmunoscintigraphic tumor localisation necessitates a major optimisation procedure to carefully balance factors such as radionuclide, anchoring site on the antibody, method of labelling and addition of radioprotective agents. Even under ideal conditions radiolytic and enzymatic degradation of the biologically active antibody cannot be avoided. The resulting radioactive fragments will exhibit organ distribution patterns different from those of the parent antibody and may pose a major obstacle to scintigraphy of certain organs such as liver, kidney and spleen.

Zusammenfassung

Die Entwicklung von radioaktiv markierten Antikörpern für die radioimmunoszintigraphische Tumorlokalisation bedingt die sorgfältige Optimierung verschiedener Faktoren, wie zum Beispiel die Wahl des Radionuklids, die Verankerungsstelle im Antikörper, die Markierungsmethode und den Zusatz von Substanzen zur Verminderung der Radiolyse. Auch unter besten Bedingungen ist mit radiolytischer und enzymatischer Degradation des biologisch aktiven Antikörpers zu rechnen. Die resultierenden radioaktiven Fragmente weisen Anreicherungsmuster auf, die von jenen des Antikörpers verschieden sind, und können somit die Radioimmunoszintigraphie von gewissen Organen wie Leber, Milz und Nieren stören oder gar vereiteln.

^* Presented at the Symposion on “Monoclonal Antibodies in Nuclear Medicine” in Freiburg, May 1-3, 1986.

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