CD1d ligation induces cell aggregation, up-regulation of Bax, and caspase-independent cell death. (A) Treatment with anti-CD1d of KMS11-CD1d but not KMS11-vector cells induces cell aggregation. (B) Immunoblotting for various Bcl-2-related proteins at the indicated time points after treatment of the KMS11-CD1d cell line with anti-CD1d 42.1 mAb. (C) Immunoblotting for cleaved caspase 8 and 9. No difference in cleaved caspase 8 products compared with baseline was observed after treatment of KMS11-CD1d with anti-CD1d for the indicated time points; similarly, no cleaved caspase 9 higher than background was observed after treatment with anti-CD1d. (D) Cell death induced by CD1d ligation of KMS11-CD1d is not inhibited by various caspase inhibitors. Data shown in all panels are representative of 3 independent experiments with similar results.