mAb ligation of CD1d triggers cell death. (A,B) Annexin⁺ cells (bottom right quadrant in the flow cytometry dot blots) detected by annexin/PI staining after ligation of the C1R-CD1d B cell line with 2 different anti-CD1d mAb at different time points compared with isotypic IgG and medium only treatment. For medium or IgG versus anti-CD1d 42.1 at 12, 24, and 36 hours, P < .01, n = 6. For CD1d 51.1, the mean plus or minus SEM of 2 experiments is shown. (C) Mitochondrial membrane potential loss detected by DiOC3 staining 24 hours after ligation with anti-CD1d 42.1 (10 μg/mL), IgG1 isotypic, or medium control. Representative of 3 independent experiments. (D) Cell death as assessed by annexin⁺ cells at 24 hours after treatment of the myeloma cell line KMS11 transfected with full-length human CD1d with different concentrations of anti-CD1d 42.1. Data shown are mean plus or minus SEM of triplicate assays and representative of 3 experiments. (E) Cell death as assessed by annexin⁺ cells at different time points after treatment of the myeloma cell line KMS11-CD1d with anti-CD1d 42.1 mAb (10 μg/mL) or IgG isotypic control. Representative of at least 4 independent experiments. (F) Mitochondrial membrane potential loss of KMS11-CD1d at 24 hours after treatment with anti-CD1d 42.1 mAb (10 μg/mL). Representative of 3 independent experiments. (G) Cell death shown as percentage of annexin⁺ cells of CD138-purified primary myeloma cells as assessed at 24 hours after treatment with 5 μg/mL anti-CD1d 42.1 (■) or medium ().