Iron forms in the supernatants of healthy volunteer monocytes (□) and HH monocytes (▪) after erythrophagocytosis and during the release experiment. At different time points during iron release, supernatants were collected, frozen, dried, reconstituted with ddH₂O, and fractionated on SE-HPLC. Radioactive iron was measured again in the eluted fractions. Iron was recovered as Hb, LMW-Fe, and ferritin. The results are expressed as percentage (mean ± SD) of the total iron present in the system (= cells + supernatant) of six experiments. Statistical analysis was by Student'st-test (★, P < .05).