Monoclonal antiidiotypic antibodies related to a murine oncofetal bladder tumor antigen induce specific cell-mediated tumor immunity.

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Abstract
Rat monoclonal antibody 6.10 recognizes a 175-kDa protein expressed in all BALB/c mouse transitional cell bladder carcinomas tested, in epithelial cells of the mouse embryo, and in a few epithelial cells of adult mice. The anitbody was used as an immunogen to generate two mouse monoclonal antibodies, 21D9 and 43A10, which bind to idiotopes on antibody 6.10 associated with the binding site for the 175-kDa antigen. The antiidiotypic antibodies induced bladder tumor-specific, cell-mediated immunity when injected into syngeneic mice, as shown by delayed-type hypersensitivity reactions in vivo and leukocyte adherence inhibition reactions in vitro. Tumor specificity was demonstrated by employing as controls a chemically induced BALB/c fibrosarcoma, MCA-1511 (MCA, 3-methylcholanthrene), and its corresponding antiidiotypic antibody, 5.96. Lymphocytes from mice sensitized with antibody 21D9 or 5.96 specifically recognized antigens in extracts of BALB/c bladder carcinoma BTCC-1660 (BTCC, bladder transitional cell carcinoma) and sarcoma MCA-1511, respectively, as shown by leukocyte adherence inhibition reactivity. This reactivity was selectively abrogated by prior treatment of the sensitized cells with the appropriate antiidiotypic antibodies and complement. An antigen recognized in vitro by antibody 21D9-sensitized lymphocytes should be separated from BTCC-1660 extract by immunoabsorption with antibody 6.10 and elution with acidic buffer. Our findings indicate that the oncofetal antigen defined by antibody 6.10 is recognized by the immune system of syngeneic mice and suggest that antiidiotypic antibodies relatd to certain oncofetal antigens can be used to immunize against syngeneic tumors.