The only gangliosides in Burkitts' lymphoma EB-3 cells is GM3. Treatment of Burkitts' l~phoma EB-3 cells with ganglosides GM1 or GM3 results in their binding to and partial incorporation into the cell membrane. About 25% of cell-associated ganglioside GMI can interact with the ricin. However, such an increase in the number of binding sites does not enhance but rather decreases the cytotoxic effect of ricin. A similar protective effect was observed when the cells were pretreated with ganghoside GM3. In contrast, the increase in ricin binding sites caused by pretreatment of the cells with neuraminidase was accompanied by increase in ricin cytotoxicity. These differences may be related to observed differences in the rate of ricin-endocytosis by native and ganglioside-treated cells.

The interaction of poly-and monoclonal antibodies against the L-chain of human Ig with Burkitt lymphoma EB-3 cells was studied using a fluorescent lipid probe, anthrylvinyl-labelled sphingomyelin, incorporated into the cell plasma membrane. Binding of the antibodies to Ig receptors on the surface was shown to induce changes in the fluorescence polarization of the probe. The high sensitivity of the method allows one to detect less than 100 antibody molecules per cell. The possibility of using cells or liposomes carrying antigens and fluorescent lipids for the determination of antibodies in solution is discussed.Lipid fluorescence; Fluorescent probe; lmmunoglobulin receptor; (Burkitt lymphoma cell)