ROS generation by reticulocytes and mature red cells. Peripheral blood cells from Sod2^+/+ and Sod2^–/– transplant recipients were incubated in the presence of the superoxide-sensitive dye DHE and the peroxide-sensitive dye H₂DCFDA for 30 minutes at 37° C, followed by FACS analysis. (Left) Peroxide production by Sod2^+/+ red cells and reticulocytes (shaded gray); and Sod2^–/– red cells and reticulocytes (black line). (Right) Superoxide production by Sod2^+/+ (shaded gray) and Sod2^–/– (black line) red cells and reticulocytes. Red cells are the major peak for each histogram, with reticulocytes forming a tail or secondary peak with higher ROS production. Plots shown are representative of 5 mice for each genotype. For each histogram: light gray tracing indicates unstained Sod2^+/+ cells; broken black tracing indicates unstained Sod2^–/– cells.