Fig. 7. Macrophages digest RBCs and raise iron level.

Macrophages engulf RBCs and digest them into hemoglobin, which further break down into heme. Heme can be decomposed into biliverdin, carbon monoxide and iron. Iron generated from heme can either promote ROS production and lipid peroxidation or released into the environment through FPN, thus raising the iron level in both macrophages and the tissue environment.