IMMUNO-FLOW CYTOMETRIC DETECTION OF THE ICHTHYOTOXIC DINOFLAGELLATES GYRODINIUM-AUREOLUM AND GYMNODINIUM-NAGASAKIENSE - INDEPENDENCE OF PHYSIOLOGICAL-STATE

The ichthyotoxic dinoflagellates Gyrodinium aureolum and Gymnodinium n agasakiense were cultured under different environmental conditions to test possible variability in immunochemical labelling intensity of cel l-surface antigens using species-specific monoclonal antibodies. Varia tion of antigen abundance (which is directly related to labelling inte nsity) at the cell surface, determined by immune-flow cytometry of cel ls labelled with FITC, appeared to be small but significant compared t o control cultures. In general, a minor decrease in FITC fluorescence was recorded during exponential growth, followed by an increase during stationary growth. FITC fluorescence was correlated with cell size, s hape and structure. This suggests a constant number of antigens per un it of cell surface. In all cultures, immunochemically labelled cells w ere distinguished clearly from unlabelled cells; immune-flow cytometri c identification is apparently not affected by growth conditions. Only at the end of the stationary growth phase in batch cultures did the F ITC fluorescence values drop, which suggests that unhealthy, dying or lysing cells may either alter the composition of the cell surface or j ust fail to express the antigen.