Transferrin white cells

Hypoproteinemia may result in low levels of serum calcium, ceruloplasmin, and transferrin. Because losses of iron are at most 0.5-1.0 mg/24 hr, even with the heaviest proteinuria, other factors must operate to produce iron deficiency and microcytic hypochromic anemia. Although the copper-binding protein ceruloplasmin is lost in the urine in nephrotic subjects and its plasma levels are low, plasma and red cell copper concentrations are usually normal. Zinc circulates mainly bound to albumin and also to transferrin, and thus the reported reduction zinc concentration in plasma, hair, and white cells in nephrotic patients is not surprising. 

Transferrins are also involved in the antimicrobial action of the white cells. Lactoferrin is an important component of neutrophils (Masson et al., 1969), and is crucial for the phagocytic activity of these cells. Thus, if lactoferrin present in the neutrophils is saturated with iron, the antibacterial action of the neutrophils is greatly compromised (Bullen and Armstrong, 1979). 

The transferrins include serum transferrin found in blood serum, ovo transferrin or conalbumin found in egg whites and lacto transferrin found in the milk of mammals. Serum transferrin has the primary role of transporting iron throughout the system from the iron storage areas to the bone marrow for incorporation into hemoglobin in the immature red blood cells. It also appears to have the function of sweeping free iron ions out of the serum to prevent iron poisoning. 

In the meantime, in 1947, Laurell and Ingelman[17] had independently purified the red protein from pig plasma and in the same year proposed the name transferrin which has since been adopted as the generic name of the proteins of this family serotransferrin (instead of siderophilin) present in blood and some external secretions, ovotransferrin (instead of conalbumin) in avian egg-white, lactotransferrin (also called lactoferrin) from milk, external secretions and leukocytes and melanotransferrin (instead of p97) in melanocyte and normal cell plasma membrane. A dozen mammalian and some frog, fish and insect serotransferrins were later isolated and characterized. 

Platelets and white blood cells (WBC) can be labeled with In to provide agents for imaging inflammatory processes and thrombi (McAfee and Thakur 1976, Keeley and Hillis 1996, Becker and Meller 2001). A weak complex is formed between the In radiometal and 8-hydroxyquinoline (oxine). Since the hn-oxine complex is weak, the metal rapidly exchanges with transferrin in the plasma. In the absence of plasma, the complex diffuses across the cell membrane and the metal binds to intracellular sites. In humans, hn-labeledWBC will accumulate at sites of inflammation and also localize in the liver and spleen. 

In-labeled white blood cells (WBC) have also been clinically used for infection and inflammation imaging. The neutral, lipid-soluble "In(oxine)3 (oxine = 8-hydroxyquinoline) complex penetrates cellular membranes and is used to label WBC. After diffusing intracellularly, the "In(oxine)3 complex dissociates and the " In is bound to nuclear and cytoplasmic proteins. Labeling of WBCs is done in plasma to avoid transchelation with transferrin in blood. The procedure consists of withdrawal of blood from patient, separation of red blood cells from white blood cells, purification of leucocytes, radiolabeling, followed by reinjection of the radiolabeled cells into the patient. The WBCs migrate to inflamed area and can lead to positive imaging. 

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