Targeting of T lymphocytes against egf‐receptor+ tumor cells by bispecific monoclonal antibodies: Requirement of CD3 molecule cross‐linking for t‐cell activation

Authors:
Publisher website
Google Scholar
Abstract
Targeting of T lymphocytes against epidermal growth‐factor‐receptor (EGF‐R)+ tumor cells was achieved by constructing a hybrid hybridoma which secretes an anti‐EGF‐R/anti‐CD3 bispecific monoclonal antibody (biMAb) of hybrid isotype (IgG1/ IgG2a). Purification of biMAb molecules from parental anti‐EGF‐R and anti‐CD3 MAbs was performed by protein‐A chromatography. The purified biMAb was able to trigger the lysis of EGF‐R+ tumor cell lines (A431, IGROV‐1, MDA‐468 and U‐87) and of NIH‐3T3 transfectants expressing human EGF‐R by cytolytic T lymphocytes, but it was ineffective in the case of EGF‐R‐negative tumor targets. Normal EGF‐R+ (keratinocytes and endometrial cells) were also susceptible to biMAb‐targeted cytolysis. However, the amount of biMAb required to induce half‐maximal cytolysis of tumor cells over‐expressing the EGF‐R molecule (A43I) was considerably lower than that required to induce lysis of EGF‐R+ tumor or normal cells which express EGF‐R at considerably lower density. The ability of such biMAbs to deliver activation signals to T cells was evaluated by Ca++ mobilization and lymphokine production experiments. The soluble anti‐EGF‐R/anti‐CD3 biMAb failed to induce intracellular Ca++ increases, which occurred only after cross‐linking induced by an anti‐mouse IgG antibody. Secretion of lymphokines (IFN‐γ, TNF‐α and GM‐CSF) was induced by contact of the biMAb‐coated effector cells with the relevant tumor target, whereas the soluble biMAb was virtually ineffective. In addition, biMAb‐coated effector cells retained the ability to recognize and to lyse EGF‐R+ tumor cells for a prolonged period of time. Our data indicate that activation of effector cells targeted by biMAbs can only occur at the tumor site, where cross‐linking of surface CD3 molecules is induced by contact with the tumor cells.

This publication has 22 references indexed in Scilit: