Synergy of ricin A chain-containing immunotoxins and ricin B chain-containing immunotoxins in in vitro killing of neoplastic human B cells

E. S. Vitetta, W. Cushley, J. W. Uhr

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A strategy is described for improving the efficacy of ricin A chain-containing immunotoxins. Highly purified preparations of ricin A chain or ricin B chain were separately coupled to anti-human immunoglobulin antibodies and the conjugates (immunotoxins) were affinity purified to eliminate free chains. Mixtures of anti-Ig-A and anti-Ig-B immunotoxins markedly synergized in vitro in their ability to kill the Ig-bearing human lymphoma cell line Daudi. In contrast, A-chain- or B-chain-containing immunotoxins of irrelevant specificity did not synergize with anti-Ig-A or anti-Ig-B immunotoxins. This finding indicates that free A or B chains do not play a major role in the synergy and that the synergy is specific. Thus, synergy depends on the specificity of the two antibodies; the lectin binding ability of a B-chain-containing immunotoxin of irrelevant specificity does not suffice. This approach of delivering ricin A chain and B chain separately to a target cell may have significant advantages in killing cells that are not effectively killed by A-chain-containing immunotoxins alone.

Original languageEnglish (US)
Pages (from-to)6332-6335
Number of pages4
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number20 I
StatePublished - Jan 1 1983


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