Evaluation of the expression of TRAIL receptors.

(A) Membrane proteins were obtained from exponentially growing HEL (H) and K562 (K) cells. After SDS/PAGE, samples were immunoblotted by using polyclonal goat antibody directed toward TRAIL-R1 and TRAIL-R2. Sizes of the molecular mass markers are indicated in kilodaltons (kd) on the left. Surface expression of TRAIL-R1, -R2, -R3, and -R4 was evaluated by flow cytometry in K562 (B), HEL (C) cell lines, and primary normal erythroblasts (D) at 6 (HEL) and 18 (K562, primary normal erythroblasts) hours after IR. Shadowed histograms represent irradiated cells stained with anti–TRAIL-RI, -R2, -R3, and -R4 antibody. Unshadowed histograms represent nonirradiated (control) cells. Negative controls are represented by cells stained with isotype-matched irrelevant goat IgG (Irr. Ab). Representative results from 1 of 4 separate experiments are shown.