FIG. 1.

A new 30-kDa protein is detected by the anti-caspase-8 MAb C15. (A) Scheme of procaspase-8 and its cleavage products. The binding sites of the anti-caspase-8 MAbs C5 and C15 are indicated. (B) The B-lymphoblastoid cell lines SKW6.4, Raji, and BJAB and the T-cell lines CEM, Jurkat 16, and caspase-8-deficient Jurkat (clone JI9.2) were stimulated with LZ-CD95L for the indicated times, followed by caspase-8 immunoprecipitation (C8-IP) using the anti-caspase-8 MAb C15 directed against the p18 subunit of procaspase-8. Western blotting of immunoprecipitates was performed using the anti-caspase-8 MAb C15 (**, Ig heavy chain; *, unspecific band). (C) SKW6.4 cells were stimulated with LZ-CD95L for different times, and procaspase-8 processing in total cellular lysates was analyzed by Western blotting using the anti-caspase-8 MAb C15. (D) B-lymphoblastoid BJAB cells were stimulated with LZ-TRAIL for different times, and procaspase-8 processing was analyzed as described for panel C. (E) Primary human T cells (day 6) were stimulated with LZ-CD95L, and procaspase-8 processing was analyzed as described for panel C (*, unspecific band).