(A) FasL concentrations in AML and CML patients. FasL was quantified by Western blotting assay by using a National Institutes of Health Image Program 1.6. Data for patients were normalized to the PBMC from 2 normal individuals, for which the data have been included at each time. (B) FasL profile. Western blot showing FasL in cells from leukemic patients. Cells were lysed in lysis buffer, separated on a 4/20% polyacrylamide gel, the protein transferred to a nitrocellulose membrane, and the membrane was probed with an anti-FasL MoAb. Fourteen patients were analyzed for FasL contained by Western blot. All the samples tested contained FasL and several also contained the truncated form of the protein. FasL (37 kD) and short FasL (sFasL, 26 kD) are indicated by arrows. Short FasL was never detected in samples from AML or normal donors.