Elevation of circulating immunoglobulin and autoantibodies in 4-month-old Mayp^Lp/Lp mice. (A) Serum immunoglobulin levels expressed as the fold increase of their concentration in Mayp^Lp/Lp (n = 5) compared with WT (n = 17) mice (± SD). Elevations of IgG1, IgG2a, and IgE are significant (P < .05; Student t test). (B) Twelve lanes, each containing identical amounts of a single extract of normal paw proteins, were subjected to SDS-PAGE and Western blot analysis with individual sera of 6 Mayp^Lp/Lp mice expressing serum immunoglobulin and of 6 WT mice. (C) Immunohistochemistry using serum from a Mayp^Lp/Lp mouse as primary antibody, showing that the cognate proteins are located in the papillary layers of the corium. Similar results were obtained for 3 additional Mayp^Lp/Lp sera. Bar, 100 μm.