FIG. 4.
FB11 binds to a different OAg epitope than Ab3, Ab52 and Ab54. (A) The binding of FB11 to decreasing concentrations of Ft LPS decreases at a much higher rate than the binding of the other IgG2a anti-OAg MAbs. Reactivity of IgG2a anti-OAg MAbs was tested by ELISA on plates coated with the indicated concentrations of LPS. Data from one of three experiments with similar results are shown. (B) Ab3, Ab52, and Ab54, but not FB11, bind to overlapping OAg epitopes. Isotype-specific competition ELISA was performed with graded concentrations of the indicated IgG2a competitors and a fixed concentration of Ab3IgAR, and the ELISA was developed with anti-IgA secondary Ab. The left panel shows the competition assay. The presence/binding of all IgG2a anti-LPS competitor MAbs to LPS was verified in a duplicate plate by developing the reaction with HRP-conjugated anti-mouse IgG2a secondary Ab (right panel). Data from one of three experiments with similar results are shown.