Autoantibody production WASp-deficient mice. (A) Fluorescent ANA titers in WASp-deficient and age-matched control mice on 129SvEv genetic background divided into 2 groups based on age (> 6 months and < 6 months). Statistical comparison was performed using the Fisher exact test. A total of 266 serum samples were tested. For the group less than or equal to 6 months old (n = 48), the mean age ± SD in days was WASp-deficient, 119 ± 35; WT controls, 104 ± 33 (P = .18). For the group more than 6 months old (n = 218), the mean age ± SD in days was WASp-deficient, 325 ± 98; WT controls, 303 ± 83 (P = .08). (B) Representative images of 129 background WASp ANA (serum dilution 1:640) with positive (B6.lpr/lpr 1:640) and negative 129 SvEv WT controls (serum dilution 1:40). Note the staining of mitotic figures by serum from the WASp-deficient mouse, suggesting the presence of anti-chromatin antibodies. (C) Kaplan-Meier analysis of the proportion of mice becoming ANA-positive at 1:640 cutoff titers over time (solid line, WT controls; dashed line, WASp-deficient mice). (D) Sera from ANA-positive mice tested for anti-dsDNA specificity by ELISA and expressed as a percent of the total tested samples per genotype. Mean age in days ± SD (not statistically significantly different) and number of mice per group are indicated (anti-dsDNA–negative, □; anti-dsDNA–positive, ■).