TRAF3 mice develop plasmacytosis. (A) Phenotypic analysis of plasma cells. Submaxillary lymph nodes (LN) and spleen lymphoid populations were analyzed by 3-color flow cytometry in a representative 14-month-old TRAF3 transgenic mouse (TRAF3) and wild-type littermate (WT). Total nucleated cells were stained for B220, Syndecan-1 and IgM surface expression and analyzed with no gate (top) or selecting the IgM null cells (bottom). Numbers indicate the percentage of cells in that gate. (B) Analysis of plasma cells in lymph nodes. Immunohistochemical analysis of a representative lymph node from a diseased TRAF3 mouse showing severe plasmacytosis. Plasma cells were identified by cytosolic Ig staining. Bars, 100 μm. (C) Plasma cell infiltrates in tissues from TRAF3 mice. Immunohistochemical analysis of the tongue (left) and pancreas (right) of a representative diseased TRAF3 mouse (top and middle panels) and a wild-type littermate (bottom panels). Left, H&E (top and bottom) or anti-IgG (middle) staining of sections of the tongue. Right, H&E staining of infiltrating plasma cell in the pancreas. Bars, 50 μm. (D) Analysis of the expression XBP-1 and IgG in purified B cells. B-cell extracts (20 μg) were analyzed by SDS-PAGE and immunoblotting. (E) TRAF3 mice develop hypergammaglobulinemia. Serum IgG_2a, IgG_2b, and IgM concentrations from TRAF3 mice (ϵ-line) and wild-type littermates (10-15 months old) were determined using isotype-specific ELISA. P values are indicated in the figure. Statistical significance was determined by unpaired Student t test.