Immunolocalization of theca antigens on Alexandrium catenella and their use to isolate cells from fixed phytoplankton samples

Murine monoclonal antibodies were generated and selected for their ability to specifically recognize theca antigens of Alexandrium catenella (Whedon et Kafoid) Balech cells. The specificity of the monoclonal antibodies for theca antigens was shown by indirect immunofluorescence and by confocal microscopic analysis. Using these antibodies we demonstrate, for the first time, the presence of different theca antigens on the cell surface. The fluorescent signal analysis suggests that these antigens differ in their distribution and quantities in the theca. Also, using the antibodies we developed a rapid method to isolate A. catenella cells from a lugol-fixed phytoplanktonic sample. The method uses a mixture of different monoclonal antibodies to bind the cells, which then are pulled off from the sample by means of a second anti-mouse antibody coupled to 0.8 μm magnetic beads.