This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by French, R. R. Articles by Glennie, M. J. Search for Related Content PubMed PubMed Citation Articles by French, R. R. Articles by Glennie, M. J.

Cooperative Mixtures of Bispecific F(ab')₂ Antibodies for Delivering Saporin to Lymphoma in Vitro and in Vivo¹

Lymphoma Research Unit, Tenovus Laboratory, General Hospital, Southampton, United Kingdom

We report that selected combinations of two or more monoclonal bispecific F(ab')₂ antibodies (BsAbs) far outperform single derivatives in the delivery of the ribosome-inactivating protein, saporin, to guinea pig L₂C leukemic cells. Throughout the work, BsAbs were constructed by thioether-linking the hinges of two Fab', one from monoclonal anti-L₂C-idiotype antibody and the other from anti-saporin antibody. The latter was either affinity-purified rabbit polyclonal or one of a panel of five mouse monoclonal antibodies. In vitro cytotoxicity studies showed that, though all derivatives were effective, the BsAb made with the polyclonal antibody was always 10 to 20 times more potent than those made with a monoclonal antibody in yielding 50% inhibition of [³H]-leucine uptake. This superior activity could be matched by selective mixtures of two or more of the monclonal derivatives. Furthermore, in immunotherapeutic delivery of saporin to tumor, a pair of BsAbs performed significantly better than did either individually.

Binding and uptake studies with radiolabeled saporin demonstrated a 20-fold increase in functional affinity when saporin was held at the cell surface by an appropriate BsAb mixture rather than by a single BsAb. In contrast, only small differences were recorded in the rate at which saporin was internalized as a result of the same maneuver. We conclude that the improved performance of combinations of BsAbs arises from their ability to provide multiple linkages between saporin molecules and cell surfaces, significantly increasing the functional affinity with which saporin is tethered to the cell, but, in this system at least, having only a minor effect on the rate at which it is internalized. Cocktails of two or more BsAbs, selected to bind to multiple epitopes on ribosome-inactivating proteins and perhaps also on unwanted cells, could provide an important new strategy in immunotherapy.

¹ This work has been supported by Tenovus of Cardiff, the Cancer Research Campaign, and Italfarmaco, Milan, Italy.

² To whom requests for reprints should be addressed.

Received 10/ 1/90. Accepted 2/19/91.

This article has been cited by other articles:

				C. H. T. Chan, J. Wang, R. R. French, and M. J. Glennie Internalization of the Lymphocytic Surface Protein CD22 Is Controlled by a Novel Membrane Proximal Cytoplasmic Motif J. Biol. Chem., October 23, 1998; 273(43): 27809 - 27815. [Abstract] [Full Text] [PDF]