INTERACTION OF CHOLERA TOXIN AND TOXIN DERIVATIVES WITH LYMPHOCYTES

Abstract

The interaction of cholera toxin and a number of toxin derivatives, containing different proportions of light and heavy toxin-composing subunits (L and H), with mouse lymphocytes was studied. Experiments with [¹²⁵I]toxin showed that a single cell can rapidly, within minutes, bind up to 40,000 molecules of toxin, the association constant was estimated to 7 ± 4 x 10⁸ liters/mol, and binding was found to be very similar at 37°C and 5°C. Immunofluorescence studies revealed that the toxin attachment is located on the cell surface, and that purified L subunit but not H subunit binds to the cells. A natural cholera toxoid, built up by aggregated L subunits, showed almost identical binding properties as toxin to the cells. Pure G_M1 ganglioside, the proposed membrane receptor structure for toxin, prevented entirely the cellular binding of both toxin and toxoid.