Targeting of T or NK lymphocytes against tumor cells by bispecific monoclonal antibodies: role of different triggering molecules.

Abstract

MAbs directed against triggering surface molecules expressed by T lymphocytes (CD3, TCR, CD2, CD28) or by NK cells (CD2, CD16) are able to induce the functional program of these cells. These MAbs represent suitable reagents to construct biMAbs directed against TAA, in order to specifically target effector lymphocytes against tumor cells. Anti-CD3/anti-EGF-R biMAbs were constructed to specifically direct T lymphocytes against EGF-R+ tumor cells. Such biMAb are able to induce cytolysis of EGF-R+ tumor cell lines (A431, IGROV, KATO-III and U-87) by cytolytic CD3+ effector lymphocytes while tumor cells having low or absent expression of EGF-R were not lysed. In addition, both cytolytic T (CD8+) cells and non-cytolytic (CD4+) IL-2-expanded lymphocytes were able to secrete lymphokines upon contact with EGF-R+ tumor cells. To target NK cells against NK resistant ovarian carcinomas, we used an anti-CD16 Mab (IgG1) together with an anti-ovarian carcinoma MAb (IgG2a), to construct biMAbs using the hybrid hybridoma technique. The hybrid IgG1/IgG2a biMAb triggered the specific lysis of relevant target cells by resting NK cells and by a subset of NK clones. In addition, some TCR gamma/delta+ clones but not TCR alpha/beta+ clones could be targeted by the biMAb.