Combination neutralising effect of antibodies against ricin <i>in vitro</i>.

<p>(<b>A</b>) Combination of pairs of antibodies, with RB34 as control (RB34: ○; RB34/RB37: ▴; RB34/RA36: ♦; RB37/RA36: ▾; RB27/RB37: ▪). (<b>B</b>) Combination of three or four antibodies, with RB34 as control (RB34: ○; RB27/RB37/RA36: •; RB34/RB37/RA36: ▴; RB34/RB37/RA36/RA32: <b>+</b>; RB34/RB37/RA36/RA33: ▪; RB34/RB37/RA36/RA35: ♦). Antibodies were premixed in equimolar ratio at several concentrations (0–10 µg/ml) and incubated with ricin (0.1 ng/ml) before exposure to Jurkat cells. Cell viability was assessed by means of luminescence assay using a Cell titer Glo luminescence kit (Promega).