Induction of functional activities of human lymphocytes by monoclonal antibodies.

Monoclonal antibodies (MoAbs) specific for surface molecules involved in lymphocyte activation, represent an useful tool for the analysis of the activation pathways of different effector lymphocytes. We have analyzed the ability of MoAbs directed against "triggering" surface molecules, such as CD3/TCR, CD2 and CD16 to induce activation of the lytic machinery in T and NK lymphocytes, using a redirected killing assay. In addition, we have constructed bispecific monoclonal antibodies (BiMoAbs) directed against both the CD3/TCR complex (or the CD16 molecule) and a tumor associated antigen expressed on the surface of ovarian cancer cells. BiMoAbs were constructed by two different approaches: a) conjugation of two distinct MoAbs by a chemical heterobifunctional agent; b) selection of hybrid-hybridomas secreting BiMoAbs. BiMoAbs were able to focus appropriate lymphoid effector cells on tumor cells expressing the relevant antigen, and to induce tumor cell lysis. Therefore, these reagents were able to confer a new specificity for a given antigen to effector lymphocytes, independently from the original one. For these properties, BiMoAbs may represent a suitable tool for new strategies of adoptive immunotherapy, based on the use of effector cells that have been specifically armed by BiMoAbs against the tumor.