Anti-cell surface monoclonal antibodies which antagonize the action of VIP in a human adenocarcinoma cell line (HT 29 cells).

Hybridoma cells have been obtained by fusing RCY 3 Ag 1-2-3 rat myeloma cells with spleen cells from a rat hyperimmunized with human adenocarcinoma cells (HT 29 cell line) grown in serum-free medium. Immunoglobulins secreted by hybridomas were screened for: (i) specific binding to HT 29 cells; (ii) their ability to inhibit the binding of [125I]-vasoactive intestinal peptide (VIP) to HT 29 cells; (iii) their capacity to modulate the cAMP production induced by VIP. The monoclonal antibodies we have obtained from clones 109-10-16 and 109-10-19 compete for the binding of radiolabelled VIP to HT 29 cells and partially inhibit the production of cAMP induced by VIP while they are ineffective in reducing the intracellular level of cAMP attained after stimulation of HT 29 cells by isoproterenol. We never found antibodies which increase the cAMP level in HT 29 cells. The binding of the purified monoclonal antibody 109-10-16 Ig gamma 2c to HT 29 cells was visualized by indirect immunofluorescence and was not present at the surface of all cells. These observations strongly support the hypothesis that the monoclonal antibodies we have characterized interact with an antigenic determinant which belongs to the VIP receptor or at least to a cell surface component closely associated with the receptor.