Low molecular weight iron-binding factor from mammalian tissue that potentiates bacterial growth.

A low molecular weight, iron-binding factor was isolated from horse liver. This host-associated iron transfer factor (HAITF) is capable of binding iron and stimulating bacterial growth by promoting iron uptake into bacteria. Also, when injected into infected animals, HAITF increases the virulence of bacterial infections. HAITF bioactivity is ubiquitous in animal tissues and present in serum. It is proposed that HAITF is a factor that inadvertently plays a role in the host-parasite competition for iron.