Disruption of Fpn1 in mouse macrophages results in tissue iron accumulation and mild anemia. Spleen (A) and liver (B) nonheme iron concentrations were measured in sex-matched 2-month-old (Fpn1^flox/flox, 7 male, 7 female; Fpn1^LysM/LysM, 7 male, 7 female) and 10-month-old (Fpn1^flox/flox, 3 male, 3 female; Fpn1^LysM/LysM, 3 male, 3 female) Fpn1^flox/flox and Fpn1^LysM/LysM mice. (C) Spleen weight/body weight ratio in 2-month-old (Fpn1^flox/flox, 6 male, 6 female; Fpn1^LysM/LysM, 5 male, 5 female) and 10-month-old (Fpn1^flox/flox, 3 male, 3 female; Fpn1^LysM/LysM, 3 male, 3 female) mice. (D) Perls' Prussian blue staining in paraffin sections of spleen and liver from Fpn1^flox/flox and Fpn1^LysM/LysM mice shows iron accumulation in Fpn1^LysM/LysM mice (arrowheads) but not in Fpn1^flox/flox mice. Scale bar represents 100 μm. (E) Western blot analysis of ferritin expression in liver and spleen of Fpn1^flox/flox and Fpn1^LysM/LysM mice. (F) Serum ferritin levels in 2-month-old Fpn1^flox/flox (3 male, 3 female) and Fpn1^LysM/LysM (3 male, 3 female) mice. Data are mean ± SEM. *P < .05. †P < .001.