Iron withholding: a defense against infection and neoplasia

Although the phenomenon of natural immunity (as contrasted to the acquired type) was also recognized during the 1880s, knowledge concerning specific physiological and biochemical mechanisms failed to develop for the next 50 years. Within the past five decades, however, investigators have described a variety of chemical systems. Examples include the alternate complement pathway, lysozyme, beta -lysins, and interferon. Another system of natural immunity, iron withholding, is the subject of this paper. Vertebrate animals have developed an elaborate yet remarkably efficient stratagen to withhold growth-essential iron from microbial and neoplastic invaders while retaining their own access to this metal. Although the present understanding of this system is based on observations first made in the early 1930s, most of the work in this field has been accomplished more recently.