Isolation of peripheral
Peripheral blood mononuclear cells were isolated from heparinized blood by density gradient centrifugation. Briefly, 5 ml of blood, diluted with histopaque (density 1.077; Sigma-Aldrich, Dorset, UK) were carefully layered on 5 ml of lymphocyte in 15 ml centrifuge tubes and centrifuged at 1900 rpm for 30 min at 4C.