Figure 2. Binding and toxin-neutralizing activities associated with F5 and F8.

(A) Relative affinities of F5 and F8 for ricin, as determined by direct ELISA in which ricin was captured in its native form on the microtiter plate wells via a surrogate receptor asialofetuin (ASF). EC₅₀ values are defined as the antibody concentration that achieved half-maximal binding. (B) F5 and F8 were mixed at the indicated concentrations with ricin (10 ng/ml) in solution and then applied to Vero cells for cytotoxicity assessment, as described in Materials and Methods. IC₅₀ values were based in the antibody concentration that conferred 50% viability. A single representative experiment done in triplicate is shown. The EC₅₀ and IC₅₀ determinations were done at least three independent times.