Liver biopsy samples were washed in RPMI-1640 to remove contaminating blood lymphocytes, manually homogenized with a plastic plunger, and treated with DNase (0.002%, Sigma) and collagenase IV (0.02%, Sigma) for 30 minutes, stirring at 37uC. The digested cell suspension was filtered through a 70 mm strainer, washed and re-suspended in R-10 medium (10% fetal calf serum).