Activated invariant natural killer T (iNKT) cells reduce anti-DNA antibodies, but not anti-cardiolipin (anti-CL) antibodies. (a) In vitro studies. Spleen cells harvested from 5-month-old BWF1 mice were cultured with αGalCer for 5 days, and supernatants tested for immunoglobulin G (IgG) anti-DNA and anti-CL antibodies, shown as the mean ± SD optical density (OD); *P <0.05 to 0.01, n = 5. Results represent two similar experiments. (b) In vivo studies. BALB/c SCID mice (4-month-old) were reconstituted with purified B-cells from iNKT cell-deficient Jα18° BALB/c mice, and injected with lipopolysaccharide and αGalCer, as described in Methods. These mice were then implanted with T-cells from Vα14Tg BALB/c mice or with T-cells from Jα18° BALB/c mice. Four days after the reconstitution, spleen cells were harvested and cultured without any further stimulation for 6 days. Culture supernatants were tested for IgG anti-DNA and anti-CL antibodies. Results represent two independent experiments, each using three mice per group. *P <0.05.