Figure 1.

In vitro cytotoxicity of ricin and its neutralization by antitoxin. (A) Ricin caused a concentration dependent cytotoxicity in Vero cell cultures. (B) Pre-incubation of ricin (3.24 ng·mL⁻¹) with the indicated concentration of antitoxin resulted in neutralization of the cytotoxic effects of ricin. LC₅₀ and EC₅₀ values were determined from the 4-parameter logistical curve fits shown and used to calculate the neutralizing ratio as described in the main text. Data are shown as mean ± SD from three independent experiments in each case.