Production and characterisation of a monoclonal antibody specific for apoptotic bodies derived from several tumour cell lines

We have recently shown that apoptotic bodies (apobodies) derived from rat c olon carcinoma cell lines (PROb) after sodium butyrate (NaB) treatment were able to cure rats with induced peritoneal carcinomatosis (Boisteau et al., 1997). A specific immune response was assumed to be involved since the ser um of cured rats contained antibodies specific for apobodies. In the presen t study, a mAb (clone 6E8) produced by immunisation of rats with apobodies strongly recognized apobodies but had little reactivity with parental tumou r cell lines, as demonstrated by enzyme-linked immunosorbent assay (ELISA), immunostaining and flow cytometry. Immunoelectron microscopy showed that 6 E8 mAb mainly stained the hyaloplasm or cytosol of apobodies. A protein was detected at 67 kDa by immunoprecipitation of apobodies with mAb, followed by immunoblotting, using serum of rats immunised with apobodies. The 6E8 mA b recognized apobodies derived from several rat or human colon cancer cell lines and a rat glioma cell line, regardless of the apoptosis stimulus used (NaB, staurosporine or UV). Our results clearly show that 6E8 mAb defines an epitope specifically generated during apoptosis, which suggests that the protein recognized may be involved in the molecular cascade of apoptotic c ell death. (C) 1999 Elsevier Science B.V. All rights reserved.