Serum anti-cardiolipin (anti-CL) antibodies are decreased in β2 microglobulin-deficient (β2m°) and CD1d-deficient (CD1d°) BWF1 mice. (a-c) β2m° or CD1d° BWF1 mice and control littermates (β2m+/+ or β2m+/-, designated as β2m+; and CD1d+/+ or CD1d+/-, designated as CD1d+) were bled and serum samples tested for serum immunoglobulin G (IgG) anti-CL antibodies: (a) 4-month-old β2m+ (n = 88) and β2m° (n = 32); (b) 6- to 8-month-old β2m+ (n = 75) and β2m° (n = 14); (c) 7- to 8-month-old CD1d+ (n = 57) and CD1d° (n = 26) mice. Each symbol represents a single mouse, and horizontal bars represent the mean U/ml for the group. The negative control mean ± SD values for anti-CL antibody in six normal BALB/c mice was 15.1 ± 5.2 U/ml. *P <0.01, Student's t-test.