Reticuloendothelial cell

Miller Scott (1985) reported marked reduction in thymus weight in rats fed dioctyltin dichloride for 8 or 12 weeks at a level of 75 mg/kg diet. Numbers of lymphocytes together with T cell subpopulations were reduced in treated rats, but no difference was seen in antibody response to sheep red blood cells in vivo. No evidence was foimd of in vitro cytocidal effects of dioctyltin dichloride on blood lymphocytes. Evans et al. (1986) dosed pregnant and non-pregnant rats for 3 weeks at 75 mg/kg diet and reported severe thymic atrophy and extensive vacuolation of reticuloendothelial cells in pregnant animals only. 

The chemical conversion of heme to bihmbin by reticuloendothelial cells can be observed in vivo as the purple color of the heme in a hematoma is slowly converted to the yellow pigment of bilirubin. 

When high-specific-activity, non-colloidal preparations are administered (a) they are partitioned characteristically between liver and bone (b) in rodents the rate of loss of the liver burden is high (halftime = 6.5 to 10.8 d) (Durbin, 1973) (c) the spleen content is low and (d) autoradiographs show uniform distribution in hepatic cells rather than of phagocytosis of radioactive particles in the reticuloendothelial cells of the liver, spleen, and bone marrow, and there is deposition on bone surfaces. 

Further details of the above study were discussed in U.S. EPA (1994). After the last exposure, methemoglobin levels were elevated in a dose-dependent manner 17 ppm, 0% to 2.9% (no different from controls) 45 ppm, 2.2% to 5.4% and 87 ppm, 4.2% to 23%. The animals exposed at 45 and 87 ppm were anemic with decreases in RBC counts, hemoglobin content, MCHb concentration, and hematocrit, and accompanying increases in erythropoietin foci, reticuloendothelial cell hypertrophy, and hemosiderin deposition in the spleen. The animals in the 87-ppm exposure group were judged cyanotic. In the 17-ppm exposure group, effects were limited to mild splenic congestion. 

Figure 14.15 Representation of the role of ceruloplasmin in mobilizing iron from reticuloendothelial cells. (From Heilman and Gitlin, 2002. Reprinted with permission from Annual Reviews.)...

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... 

Genetic mannosidosis has been described in man, Angus cattle and Murray Gray cattle, and is characterized by a deficiency of a-mannosidase leading to storage of excess mannose-rich oligosaccharides in lysosomes. Pathologically, there is vacuolation of reticuloendothelial cells in the liver and lymph nodes, pancreatic exocrine cells, and neurons. Affected cattle are ataxic, uncoordinated, fail to thrive, and die in the first year of life. 

Heme is mainly found in the human organism as a prosthetic group in erythrocyte hemoglobin. Around 100-200 million aged erythrocytes per hour are broken down in the human organism. The degradation process starts in reticuloendothelial cells in the spleen, liver, and bone marrow. 

Physiologically, immunohaematopoietic stem cells give rise to progenitors that mature to recognizable megakaryocytes in the marrow. The latter release platelets into the circulation where they have a mean life-span of 10 days after which they are removed by the reticuloendothelial cells of the spleen, liver and bone marrow. There are three broad categories giving reduced counts. 

The flagellate leishmania is transmitted to humans by the bite of the female sandfly of the genus Phlebotomus. Three principal diseases result from infection with Leishmania spp. L. donovani causes visceral leishmaniasis (kala-azar) L. tropica and L. major produce cutaneous leishmaniasis, and L. braziliensis causes South American mucocutaneous leishmaniasis. In visceral leishmaniasis, the protozoan parasitizes the reticuloendothelial cells, and this results in an enlargement of the lymph nodes, liver, and spleen the spleen can become massive. Cutaneous leishmaniasis remains localized to the site of inoculation, where it forms a raised disfiguring ulcerative lesion. South American leishmaniasis is variable in its presentation. It is characterized by ulceration of the mucous membranes of the nose, mouth, and pharynx some disfiguring skin involvement also is possible. 

Suramin is not absorbed from the intestinal tract and is administered intravenously. Although the initial high plasma levels drop rapidly, suramin binds tightly to and is slowly released from plasma proteins, and so it persists in the host for up to 3 months. Suramin neither penetrates red blood cells nor enters the CNS. It is taken up by the reticuloendothelial cells and accumulates in the Kupffer cells of the liver and in the epithelial cells of the proximal convoluted tubules of the kidney. It is excreted by glomerular filtration, largely as the intact molecule. 

Absorption of clofazimine from the gut is variable, and a major portion of the drug is excreted in feces. Clofazimine is stored widely in reticuloendothelial tissues and skin, and its crystals can be seen inside phagocytic reticuloendothelial cells. It is slowly released from these deposits, so that the serum half-life may be 2 months. 

Perfluorocarbons. In 1966, it was demonstrated (27) that a laboratory mouse could survive total immersion in a perfluorochemical (PFC) solution. This material, similar to commercial Teflon, is almost completely inert and is insoluble in water. A water-soluble emulsion was prepared that could be mixed with blood (28), and in 1968 (29) the blood volume in rats was completely replaced with an emulsion of perfluorotributylamine [311-89-7], C12F27N. The animals survived in an atmosphere of 90—100% 02 and went on to long-term recovery. However, the 02 content of the perfluorochemicals has a linear dependence on the partial pressure of oxygen, P, as can be seen in Figure 1. The very high 02 tension required to transport physiologic amounts of 02 (12) and the propensity of the perfluorocarbon to be taken up by the reticuloendothelial cells were considered to be severe limitations to the development of clinically useful perfluorocarbon blood substitutes (30). 

Transferrin also has to cope with the iron liberated on breakdown of iron enzymes. It carries iron from the breakdown sites of hemoglobin in the reticuloendothelial cells of spleen and liver back to the sites in bone marrow for the synthesis of hemoglobin. Serum transferrin accounts for about 4 mg of body iron in humans, but delivers some 40 mg of iron daily to the bone marrow. 

Although the mechanisms involved are not yet fully understood, one elimination process of IgG as proteins is a slow proteolytic degradation this takes place predominantly in hepatic and reticuloendothelial cells. 

Encouraged by the greatly enhanced intake of macrophage-taigeted glucocerebrosidase by reticuloendothelial cells, we initiated an investigation to... 

Thorotrast (colloidal ThC>2) was once used as a radiopaque agent in medicine (see Radiopaques). Its injection in a dose of 2.0—15.0 g caused rises in body temperature, nausea, and injury to tissues at the injection site, followed by anemia, leukopenia, and impairment of the reticuloendothelial system. After intravenous administration, thorotrast particles are taken up by reticuloendothelial cells of the liver and spleen. Thorotrast is virtually not eliminated from the body (91). Between 1947 and 1961,33 cases of cancer of the liver, larynx, and bronchi and sarcoma of the kidneys, developing from 6 to 24 years after thorotrast administering, have been described in the literature (92). 

Mononuclear phagocytes (macrophages, Kupffer cells, spleen or lymph node) and sinusoidal or other specialized endothelium remove IgG from plasma, most frequently as IgG-containing immune complexes, IgG aggregates, or IgG bound to cell-associated epitopes [66-69], The initial binding event often occurs between the Fc portion of the IgG molecule and specific Fc receptors (FcyR) on reticuloendothelial cells (Figure 11.2). 

Other potential uses for iron chelators are reducing post-ischaemic perfusion injury [23], organ transplantation [24] and graft versus host disease [25], as anticancer agents through their effect on cell proliferation [26], mobilizing iron from the reticuloendothelial cells in the anaemia of chronic disease [27], and selective metalloenzyme inhibitors of lipoxygenase and ribonucleotide reductase. 

Thermosensitive block copolymer nanoparticles containing doxorubicin increased cytotoxicity against Lewis lung carcinoma cells when activated by heating above the LCST [139], Chitosan was chemically conjugated to NIPAAm/vinyl laurate copolymer to enhance gene transfection in mouse myoblast cells [140]. Upon i.v. administration, poly(NIPAAm) nanoparticles are taken up by the reticuloendothelial cells of the liver and mild inflammatory and fibrotic responses are observed... 

---