Iron metabolism Total body iron 4 5 gm

Iron metabolism: Total body iron: 4 -5 gm Distribution of body iron: q 65 -70% in Hb form (1 gm Hb contain 3. 34 mg iron, 100 ml blood contain about 15 gm Hb & about 50 mg iron) q 3 -4% in myoglobin q 15 -30% in stored form q 1% various heam compounds Plasma iron level: 130 µg/dl in men 110 µg/dl in women

Daily requirements of iron: q Children >15 mg/day q 4 -10 years >10 mg/day q Male more than 19 years >10 mg/day q Female: During reproductive age, pg, lactation : >18 mg/day Sources of iron: Heme iron: Fish, meat, chicken Non-heme iron: Vegetable, grains, cereals

Iron transport: Iron + Apotransferrin = Transferrin (in plasma) Iron + Apoferritin= Ferritin or storage iron (in cell cytoplasm) q Extremely insoluble form of iron in the storage pool are called Hemosiderin Daily loss of iron: 0. 6 mg of iron per day, mainly into the feces. Additional menstrual loss of iron in women to an average of about 1. 3 mg/day

Fig: Iron transport & metabolism

Iron absorption: q Actively absorbed from small intestine. Almost all iron absorbed from duodenum q Very little (about 0. 75 mg for men & 1. 5 mg for women) of the 15 -25 mg ingested iron is actually absorbed q Can be absorbed either as heme or as free iron. Iron absorption depends on body’s iron content q Iron absorption depends on the amount of intracellular (apoferritin) & extracellular transport protein (apotransferrin), compared to the amount of ferritin

q If large amount of transferrin is available, iron can be transported rapidly from erythrocytes to plasma q If little transferrin is available, most of the iron remains trapped in the erythrocytes as ferritin & eventually excreted from the body when cells are desquamated q When are stores are depleted, such as after hemorrhage, transferrin synthesis by liver (as β-globulin)

Factors affecting iron absorption: q Iron in ferrous form more soluble & readily absorbed than ferric form q Phytates, tannins, phosphates & oxalates decrease iron absorption q Amino acid & vitamin C enhance iron absorption q Partial or total gastrectomy impairs iron absorption q Malabsorption syndrome impairs iron absorption

Consequences of iron deficiency: v Microcytic hypochromic amaemia v Impaired cell mediated immunity v Reduced resistant to infection

Immunity:

Fig: Formation of antibodies & sensitized lymphocytes by a lymph node in response to antigens

Fig: time course of antibody response (by primary & secondary immune response)

Fig: binding of antigen molecules to one another by bivalent antibodies

Fig: Structure of the typical Ig. G antibody

Fig: Cascade of reactions during activation of classic pathway of complement

(APC) Fig: Activation of T cells requires interaction of T cell receptors with an antigen that is transported to the surface of APC by MHC protein

Fig: Regulation of immune system

Fig: Direction destruction of an invading cell by sensitized lymphocytes