Binding of polyclonal and monoclonal anti-isotype I antibodies to A domain isotypes I – VII. Microtitre dishes were coated with A domains isoype I (closed squares), isotype II (closed circles), isotype III (open squares), isotype IV (open circles), isotype V (closed triangles), isotype VI (open diamonds), and isotype VII (open triangles) at the indicated concentrations. Wells were then blocked and then incubated with (a) polyclonal rabbit anti-isotype I A domain antibodies, or mouse monoclonal anti-isotype I A domain antibodies 1F9 (b), 1G8 (c), 7C5 (d), 1E6 (e), and 7B7 (f). Bound antibodies were detected with either HRP-conjugated goat anti-rabbit IgG antibodies (a) or HRP-conjugated goat anti-mouse IgG antibodies (b-f), followed by TMB substrate. Graphs are representative of three separate experiments.