Transfer of ricin toxicity by spleen cells

The ability of spleen cells to internalise ricin and release it in a form capable of killing an untreated cell population has been studied. Potential donor cells were incubated with a range of ricin concentrations and the amount of ricin subsequently released was found to be related to the ricin concentration of the primary incubation. Ricin release was detected either by using radiolabelled toxin or by measuring its cytotoxic effects. Cells which, after incubation with ricin, were washed with lactose or anti-ricin IgG had a slightly reduced ability to transfer the toxin to other cells, suggesting that much of the ricin had been internalised by the donor cells. The presence of 100 mM lactose in the incubation medium was unable to inhibit the uptake of ricin and did not prevent the release of competent toxin. Cells carrying the toxic material were lethal to animals and in vitro the released toxin was as susceptible to inactivation by anti-ricin IgG as was free ricin.