Re‐targeting of human lymphocytes expressing the T‐cell receptor gamma/delta to ovarian carcinoma cells by the use of bispecific monoclonal antibodies

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Abstract
TcR gamma/delta+ lymphocytes represent a small subset homogeneously composed of cytolytic T cells displaying unique motility and homing properties. Since the lytic machinery of these cells can be efficiently triggered by monoclonal antibodies (MAbs) directed to the TcR gamma/delta, such MAbs were used for the construction of bispecific MAbs in conjunction with an MAb specific for ovarian carcinoma cells. Hybrid hybridomas were obtained by fusing the Mov19 MAb (IgG2a)‐producing hybridoma with either GI (IgG2a) or A13 (IgG1) hybridomas, secreting MAbs specific for 2 peripheral blood subsets of TcR gamma/delta+ lymphocytes. Hybrid hybridomas producing bispecific MAbs were screened according to their ability to induce ovarian carcinoma (IGROVI) target cell lysis by GI+ or A13+ T cell clones, respectively. The Gl‐derived GM33.9 bispecific MAb induced selective lysis of Mov19+ ovarian carcinoma target cells only by GI+ clones, whereas the A13‐derived AM 18.4 MAb was effective only in combination with A13+ clones. Neither the anti‐TcR gamma/ delta nor the Mov19 parental MAbs (used alone or in combination) induced target‐cell lysis. The hybrid nature (IgG1/ lgG2a) of the AM 18.4 bispecific MAb was indicated by 2‐color immunofluorescence experiments. Thus, both ovarian carcinoma and A13+ effector cells were double stained by AM18.4 bispecific MAb followed by PE‐conjugated anti‐IgG1 and FITC‐conjugated anti‐IgG2a second reagents. Polyclonal TcR gamma/delta+ cells were obtained by direct stimulation of peripheral blood mononuclear cells with Sepharose bead‐conjugated anti‐TcR gamma/delta MAbs and IL‐2. The lines so obtained contained more than 90% of TcR gamma/delta+cells after 4 weeks of culture, with an increase in TcR gamma/ delta+ cell numbers ranging from 200 to 1,000‐fold. These TcR gamma/delta+ cell lines efficiently lysed ovarian carcinoma target cells in the presence of bispecific MAb and may therefore represent a suitable source of effector cells for induction of ovarian carcinoma cell lysis.

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