Iron polymers impair the function and maturation of macrophages

An inhibitory effect of iron salts on various immune functions in vitro has been reported in several laboratories during the last years. This work extends such observations by showing that iron citrate, but not sodium citrate, inhibits the function and maturation of murine macrophages (MOs). However, such inhibition is only observed in the presence of ferric citrate with a metal-to-ligand molar ratio of 1:1, but not with ferric citrate with a metal-to-ligand molar ratio of 1:10 in which the hydrolyzation and polymerization of iron in physiological solutions is prevented. Accumulation of ferric iron on the cytoplasm of MOs was observed, but only in the group of MOs treated with ferric citrate 1:1. Increasing the concentration of serum in the culture medium diminished the inhibitory effect of ferric citrate 1:1. The inhibitory capacity of iron polymer was probably associated to its ability to both interact with the cell constituents of the cytoplasm and stimulate lipid peroxidation.