Selective cytotoxic activity of immunotoxins composed of a monoclonal anti-thy 1.1 antibody and the ribosome-inactivating proteins bryodin and momordin

Abstract

The ribosome-inactivating proteins, bryodin, from Bryonia dioica, and momordin, from Momordica charantia, were coupled by a disulphide bond to a monoclonal anti-Thy 1.1 antibody (OX7). Both immunotoxins were specifically cytotoxic to the Thy 1.1-expressing mouse lymphoma cell* line AKR-A in vitro. The OX7-bryodin immunotoxins were the more powerfully toxic and reduced protein synthesis in AKRA cells by 50% at a concentration of 1-4 x 10‑11 M as compared with 1 x 10‑9 M for the OX7-momordin immunotoxins. Neither of the immunotoxins was toxic to mouse lymphoma EL4 cells, which lack the Thy 1.1 antigen, at concentrations up to 3 x 10‑8 M. Further, bryodin and momordin immunotoxins made from an antibody (RIO) of irrelevant specificity were without effect on AKR-A cells. © 1988 The Macmillan Press Ltd.