Spontaneous anti-nuclear antibodies in WT and mutant mice with germline or conditional knockout of Fcgr2b. (A) Levels of anti-nuclear antibodies of IgG classes in 10 month old WT and mutant mice with germline or conditional knockout of Fcgr2b (16~27 mice per group) were analyzed by ELISA, and presented as O.D. values (symbols represent O.D. values of individual mice and thick horizontal lines represent the means). ** p < 0.01, *** p < 0.001, ANOVA with Dunnett’s post hoc comparing each group to the “WT” group. (B) Increased anti-nuclear antibodies levels in some Fcgr2b−/− mice. Hep-2 human epithelial cells were stained with 1:100 diluted sera from 8–9 month old WT and Fcgr2b−/− mice, followed by FITC conjugated goat anti-mouse IgG. Anti-nuclear IgG antibodies were detected in about half (9/18) Fcgr2b−/− mice, whereas none of 5 wild-type mice were positive in this analysis (p < 0.05, Chi-square test).