Anti-FD4 idiotypic antibody mimicking human gastric cancer-associated antigen.

Rabbits were immunized with the Fab fragment of a murine monoclonal antibody (McAb) PD4 against human gastric cancer to produce anti-PD4-idiotypic antibody (alpha PD4-Ab2). The alpha PD4-Ab2 could not only competitively inhibit binding of McAb PD4 to gastric cancer cell MGC803, but also induce delayed-type hypersensitivity (DTH) to MGC803 in mice. Spleen cells of mice immunized with alpha PD4-Ab2 were fused with myeloma cell SP2/0 to form hybridoma secreting Ab3 which could be bound to target cell MGC803. McAb C7-Ab3, one of the Ab3, could selectively react with a 40 kD tumor-associated antigen located on MGC803 cell membrane, as well as McAb PD4. The results indicate that alpha PD4-Ab2 possesses determinants (internal image antigen) similar to those on MGC803, and could mimic human gastric cancer-associated antigen.