FIGURE 4.

IPSE/α-1 is an immunoglobulin-binding protein with highest affinity to IgE. A, IPSE/α-1 binds to immunoglobulins and transferrin (Tf) in human serum. Western blots of human serum were incubated with IPSE/α-1 followed by labeled streptavidin (SAV-AP) or labeled α-human IgG. Proteins were stained with AuroDye and india ink. B, IPSE/α-1 binds to various immunoglobulin isotypes. Strips with blotted human polyclonal IgE, IgG, IgA, and IgM were incubated with the respective anti-isotype antibodies or IPSE/α-1 followed by SAV-AP. Controls: secondary antibody (C1), SAV-AP (C2). C, dotted IgG (G) and IgE (E) were incubated with labeled IPSE/α-1 followed by SAV-AP.