Effects of Fas triggering by anti-Fas MoAb CH11 on p210bcr/abl protein expression and on susceptibility to apoptosis of total and CD34⁺ BM cells from a representative patient with CML in chronic phase who had optimal response to IFN-α. (A) Immunoblotting of p210 from total BM cells (upper) and Coomassie-blue staining to document equal protein loading (lower). P145 c-abland actin proteins are used as controls for constant protein loading and absence of degradation. (B) Agarose gel stained with ethidium bromide after electrophoresis of low-molecular-weight DNA extracted from a constant number of total BM cells. Cell lysates and low-molecular-weight DNA were obtained from the same plates for both (A) and (B) experiments. (C) In situ TdT assay of CD34⁺cells treated as indicated; bars represent the mean number of apoptotic cells determined in triplicate experiments ± standard error of mean (SEM). Statistical analysis (paired t-test) showed P< .05 for control versus Fas triggering alone and after addition of any IFN-α concentration and for Fas triggering versus IFNα 1,000 U/mL + Fas triggering. Total BM and CD34⁺ cells were cultured for 48 hours in the presence of the indicated concentrations of IFN-α. MoAb CH11 was used at a concentration of 1 μg/mL.