Studies on the Distribution of Membrane Antigens in Rat Colonocytes and Colonic Cancer Cells : Analysis with Monoclonal Antibodies

In order to define antigen distribution on the surface membrane of colonocyte, four monoclonal antibodies which reacted with colonocytes were established. Three out of the four monoclonal antibodies reacted with the microvillus membrane, whereas the remaining one reacted with the laterobasal membrane. The restricted reactivity of monoclonal antibody 522 (IgG2b) and antibody 423 (IgG1) were confirmed by using the immunoelectron microscopic technique. Antibody 522 reacted with the microvillus membrane and the core of microvilli, which recognized a 66K dalton glycoprotein by the radioimmunoprecipitation and dot blotting method, whereas antibody 423 mainly reacted with the laterobasal membrane antigen. It was suggested that the 66K dalton glycoprotein was not homologous to human carcinoembryonic antigen or its associated antigens by its molecular profile and tissue localization. It was shown that antibody 423 did not recognize the secretory component. In 1, 2-dimethylhydrazine induced rat colonic cancer cells, it was demonstrated that both the 66K dalton glycoprotein and the antibody 423 corresponding antigen were expressed on the entire cell surface membrane showing the loss of the polarity, which was observed in the antigen distribution on normal colonocyte membrane. The animal model developed in this study will be useful for the investigation of the cellular mechanism responsible for the aberrant polarity in colonic cancer cells. In addition, this model may be useful in the analysis of immuno-targetting therapy by employing the monoclonal antibody