Detection of increased sTRAIL levels in sera of IFNα-treated patients. (A) Serum samples obtained from 6 healthy donors and 6 stage IV metastatic melanoma patients were collected either prior to or 24 hours after IFNα administration and then analyzed for sTRAIL content by ELISA. The figure shows the mean values of averaged duplicate determinations. (B) PBMCs obtained from 2 different patients (collected either prior to or 24 hours after IFNα infusion) were lysed as described in “Patients, materials, and methods” and the levels of intracellular TRAIL determined by ELISA. The mean values of TRAIL levels associated to PBMC pellets are shown.