Selective killing of normal or neoplastic B cells by antibodies coupled to the A chain of ricin

Highly specific antibodies (affinity-purified or hybridoma) directed against cell surface immunoglobulins on normal or neoplastic murine B lymphocytes were covalently coupled to the A chain of the plant toxin ricin. Such conjugates containing antibodies specific for IgM, for either of the two allotypes of IgD, or for the idiotype of the B cell tumor BCL ₁ rapidly bound in vitro to cells expressing the corresponding surface antigen and inhibited protein synthesis in such cells. The results demonstrate that A chain-coupled anti-idiotype antibody may be useful as a tumor-specific cytotoxic agent.