High concentration of IgM, IgE, and autoimmune antibodies in adult Itchy mice. (A) Serum Igs were measured in individual preimmune WT, Itch^+/−, and Itch^−/− mice by enzyme-linked immunosorbent assay (ELISA). Results are expressed as mean fold increase of relative absorbance (OD₄₀₅) over WT mice. **P < .01. (B) Antinuclear antibodies were detected by ELISA in the sera of WT and Itch^−/− mice. (C,D) WT, Itch^+/−, and Itch^−/− mice were immunized with Th2 antigen OVA-alum (C) or KLH-MPL/TDM (D), and the concentration of Ag-specific Igs was measured 3 weeks later by ELISA. Preimmune background is shown as dotted lines for panel D. Symbols throughout are as follows: × indicates WT mice; ○, Itch^+/− mice; and ▲, Itch^−/− mice.