FIG. 3.

24B11 and R70 block ricin attachment to polarized human lung epithelial cells. Fluorescein-labeled ricin (2.5 μg/ml) was mixed with the indicated MAb and then applied at 4°C to the apical surface of A459 cells grown on permeable Transwell filters. After 1 h, the monolayers were washed, fixed with paraformaldehyde, and visualized en face using a Zeiss Axioskop II fluorescence microscope. A459 cell monolayers treated with (A) ricin in the absence of MAbs, (B) ricin plus 24B11, (C) ricin plus R70, (D) ricin plus TFTB-1, or (E) ricin plus MOPC-21, an IgG1 of irrelevant antigen specificity, or (F) received no ricin treatment. The scale bar (A) applies to all panels.