<P> In response to a systemic bacterial infection, the immune system initiates a process known as iron withholding . If bacteria are to survive, then they must obtain iron from their environment . Disease - causing bacteria do this in many ways, including releasing iron - binding molecules called siderophores and then reabsorbing them to recover iron, or scavenging iron from hemoglobin and transferrin . The harder they have to work to get iron, the greater a metabolic price they must pay . That means that iron - deprived bacteria reproduce more slowly . So our control of iron levels appears to be an important defense against most bacterial infections; there are some exceptions however . TB causing bacterium can reside within macrophages which are an iron rich environment and Borrelia burgdorferi utilises manganese in place of iron . People with increased amounts of iron, like people with hemochromatosis, are more susceptible to some bacterial infection . </P> <P> Although this mechanism is an elegant response to short - term bacterial infection, it can cause problems when inflammation goes on for longer . Since the liver produces hepcidin in response to inflammatory cytokines, hepcidin levels can increase as the result of non-bacterial sources of inflammation, like viral infection, cancer, auto - immune diseases or other chronic diseases . When this occurs, the sequestration of iron appears to be the major cause of the syndrome of anemia of chronic disease, in which not enough iron is available to produce enough hemoglobin - containing red blood cells . </P> <P> Most well - nourished people in industrialized countries have 4 to 5 grams of iron in their bodies (∼ 38 mg iron / kg body weight for women and ∼ 50 mg iron / kg body for men). Of this, about 6997250000000000000 ♠ 2.5 g is contained in the hemoglobin needed to carry oxygen through the blood, and most of the rest (approximately 2 grams in adult men, and somewhat less in women of childbearing age) is contained in ferritin complexes that are present in all cells, but most common in bone marrow, liver, and spleen . The liver's stores of ferritin are the primary physiologic source of reserve iron in the body . The reserves of iron in industrialized countries tend to be lower in children and women of child - bearing age than in men and in the elderly . Women who must use their stores to compensate for iron lost through menstruation, pregnancy or lactation have lower non-hemoglobin body stores, which may consist of 6996500000000000000 ♠ 500 mg, or even less . </P> <P> Of the body's total iron content, about 6996399999999999999 ♠ 400 mg is devoted to cellular proteins that use iron for important cellular processes like storing oxygen (myoglobin) or performing energy - producing redox reactions (cytochromes). A relatively small amount (3--4 mg) circulates through the plasma, bound to transferrin . Because of its toxicity, free soluble iron is kept in low concentration in the body . </P>

Where is most of the iron in a person's body located