Reticuloendothelial macrophages

They interfere with the ability of reticuloendothelial macrophages to attack and destroy antibody-coated cells. 

The life span of the human erythrocyte is -120 days (Chap. 1), in other words with -0.85% of that total are broken down each day in the reticuloendothelial (RE) cells of the spleen, liver, and bone marrow. The erythrocytes are lysed inside the digestive vesicles of the reticuloendothelial (macrophage) cells and the hemoglobin is hydrolyzed. The globin is hydrolyzed to amino acids, and the heme is metabolized as follows. 

Polyanionic polymers can enter into biological functions by distribution throughout the host and they behave similar to proteins, glycoproteins and polynucleotides which modulate a number of biological responses related to the host defense mechanism. These are enhanced immune responses, and activation of the reticuloendothelial system (RES) macrophages. 

Fibronectin is an extracellular matrix protein that mediates a variety of cellular effects. It is important in cell-cell and cell-substratum interactions ( 3.9), mediates reticuloendothelial cell activity and binds both to Clq (the first component of complement) and to bacteria. It also increases the tu-mouricidal activity of macrophages and activates complement receptors, by regulating the binding of C3b-coated particles to neutrophils. It may mediate attachment of Staphylococcus aureus to neutrophils and may also play a role as an adhesion factor, promoting the adhesion of neutrophils to surfaces. Fibronectin mRNA (8.7-8.8 kb) is detected only at low levels in... 

About 70% of the total body store of iron (-5 g) is contained within erythrocytes. When these are degraded by macrophages of the reticuloendothelial (mononuclear phagocyte) system, iron is liberated from hemoglobin. Fe can be stored as ferritin (= protein apoferri-tin + Fe ) or returned to erythropoiesis sites via transferrin. 

C. Turnover of RBCs by the reticuloendothelial (RE) system (peripheral macrophages, spleen, and liver) and degradation of cytochromes in cells throughout the body necessitates the degradation of heme. 

In addition, polyelectrolytes such as poly(acrylic acid-alt-maleic anhydride) (pyran) are reticuloendothelial stimulants, induce resistance to tumor growth [462,463] and show interferon-inducing ability and antiviral activity. The pyran activity may be dependent upon molecular weight. Low molecular weight materials of narrow polydispersity activate macrophages however antitumor activity does not appear to be molecular weight dependent [460]. 

It is well established that size, charge, and chemical composition of liposomes affect their fate in vivo [306], To manipulate their biodistribution and/or drug release, liposomes of different structures have been prepared, including those sensitive to changes in pH [307, 308] or temperature [309,310]. Compared to soluble polymers discussed in previous chapters, liposomes, when applied i.v., are captured by a substantially greater extent by the specialized cells (macrophages) of the reticuloendothelial system (RES) [311]. The removal of liposomes from the bloodstream takes place by nonspecific endocytosis (phagocytosis) [312],... 

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