Ricin neutralization in cell-free assays. Neutralization of ricin biological activity by 43RCA (diamond, solid line), anti-dgRCA-A IgG (square, dotted line), or non-specific murine Ig (triangle, solid line). Dilutions of the antibodies were mixed with whole ricin and incubated with ricin (4.0 nM) before adding to the translation assay. Luminescence was measured after 90 min at 37°C. Values were calculated as the % control [(CPS treated sample/CPS untreated, no ricin control) × 100]. Results represent the average ± S.D. for three individual experiments.