Heinz bodies in Prx II^–/– mice. (A) RBCs stained with brilliant cresyl blue. Heinz bodies (dark inclusions within the RBCs) were found only in Prx II^–/– mice. Original magnification, × 1000. (B) Heinz body formation in homozygous (⋄), heterozygous (▪), and wild-type (▵) mice from 1 to 12 weeks of age. Bars represent SEMs.