Serum anti-dsDNA autoantibodies and rheumatoid factor (RF) are increased in β2 microglobulin-deficient (β2m°) BWF1 mice. β2m+/+ (n = 18 female and 12 male, closed circles), β2m+/- (n = 30 female and 28 male, triangles), and β2m-/- (n = 11 female and 10 male, open circles) mice were bled and serum samples tested for IgG anti-dsDNA antibody and RF. (a) Results are expressed as the percent of mice with autoantibodies, using a cutoff level of the mean + 4 SD optical density (OD) value in sera from six normal age-matched BALB/c mice. Results pooled from male and female mice are shown (*P <0.05, **P <0.01; Fisher's exact test). (b) Results of autoantibodies are shown as the mean ± standard error of log U/ml in male and female mice separately (*P <0.01 to 0.05, **P <0.001, Student's t-test).