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PubMed1992

Impaired in vitro accumulation of mercury in erythrocytes of acatalasemic mice.

In order to elucidate the role of erythrocyte catalase in the accumulation of mercury in erythrocytes, labeled erythrocytes and plasma were prepared by exposing normal and acatalasemic mice to radioactive mercury vapor (203Hg0: 6.8mg/m3) for 30 min. Labeled erythrocytes (or plasma) were mixed with unlabeled plasma (or erythrocytes) of normal or acatalasemic mice and incubated at 0 degrees C for 1 h. After incubation, the radioactivity of mercury in the erythrocytes and the plasma was measured by a gammascintillation counter. When labeled erythrocytes were incubated with unlabeled plasma, the ratio of mercury transferred from acatalasemic erythrocytes to normal plasma (11.6%) or to acatalasemic plasma (13.3%) were significantly higher than that from normal erythrocytes to normal plasma (1.8%) or to acatalasemic plasma (2.2%). When labeled normal (or acatalasemic) plasma was incubated with unlabeled normal or acatalasemic erythrocytes, the uptake of mercury by acatalasemic erythrocytes from normal plasma was 2.0%, and 1.2% from acatalasemic plasma, which tended to be lower than that by normal erythrocytes from normal plasma (3.4%) or from acatalasemic plasma (2.2%). The results indicated impaired accumulation of mercury in acatalasemic erythrocytes, suggesting the importance of catalase in taking up mercury in erythrocytes and protecting other organs from toxic effects of metallic mercury.

Acatalasia↗

PubMed1977

[Favourable erythrocyte rheology in patients with glucose-6-phosphate dehydrogenase deficiency (author's transl)].

The rheological properties of erythrocytes of 6 patients with glucose-6-phosphate dehydrogenase deficiency were studied. A method of filtration and measurements of viscosity of erythrocyte suspensions with a hematocrit of 80% were used. The erythrocytes of all patients were more flexible than the erythrocytes of healthy controls. The erythrocytes of the patients passed the polycarbonate filters with a pore diameter of 5 micron more rapidly and showed a lower viscosity of erythrocyte suspensions. The increased flexibility of erythrocytes was due to a lower hemoglobin content which was measured in isolated ghosts. After incubation of the cells with acetylphenylhydrazine, Heinz bodies formed in the erythrocytes of controls. The flexibility of these cells decreased markedly. Though more Heinz bodies were found in the erythrocytes of the patients when the cells were incubated under identical conditions, even these erythrocytes became less rigid than the erythrocytes of controls. From these results we condlude that the more flexible erythrocytes of the patients could pass the splenic sinus even when they contain Heinz bodies. The rheological properties of the erythrocytes explain why splenectomy is not efficient in glucose-6-phosphate dehydrogenase deficiency.

Blood Viscosity↗

PubMed1978

Influence of mouse age and erythrocyte age on glutathione metabolism.

In order to determine whether the biological age of a mouse influences erythrocyte metabolism and erythrocyte aging in vivo, blood samples were collected from male C57/BL6J mice of different biological ages ranging from mature (10 months) to "very old" (37 months). In the very old mouse, compared with the mature mouse, the erythrocyte survival time was decreased, erythrocyte densities were increased, the concentrations of total free thiol and reduced glutathione, and glutathione reductase activity were decreased. Erythrocytes were separated into different density (age) groups by phthalate ester two-phase centrifugation or by albumin density-gradient centrifugation. The density-age relationship of erythrocytes was established by pulse-labelling with 59Fe in vivo and by subsequent determinations of specific radioactivity of erythrocyte fractions of different densities prepared during a chase period of 60 days. The age of erythrocytes in mice of all ages was directly related to density. Also, in older erythrocytes compared with younger erythrocytes, decreased concentrations of total free thiol and reduced glutathione, and decreased glutathione reductase activity were observed. These were the lowest in the old erythrocytes of very old mice. These results in aging erythrocytes from aging mice suggest that the glutathione status the erythrocyte may be an index of aging, not only of the cell but also of the organism.

Aging↗

PubMed1994

Erythrocyte deformability has no influence on the rate of erythrophagocytosis in vitro by autologous human monocytes/macrophages.

Erythrocytes with decreased deformability are known to be rapidly removed from the circulation by splenic macrophages. The exact mechanism is, however, not well understood. We have analysed the phagocytosis of less-deformable erythrocytes by macrophages in vitro. Human monocytes/macrophages were isolated from peripheral blood and cultured for a total time of 6 h at 37 degrees C with 5% CO2. Autologous erythrocytes of the rhesus positive donor were rigidified by heat treatment (47 degrees C for 1 h). The change in erythrocyte deformability was assessed with a filter aspiration technique; the membrane elastic modulus was found to be increased about 2.5-fold. For controls, untreated erythrocytes and erythrocytes incubated with anti-RhD-antibodies were prepared. The rate of phagocytosis during 2 h at 37 degrees C and 5% CO2 was 0.74 +/- 0.59 (erythrocytes per monocyte/macrophage) for controls, 3.58 +/- 2.72 for anti-RhD-loaded erythrocytes and 0.82 +/- 0.74 for heat-treated erythrocytes, respectively. We conclude that decreased erythrocytes deformability does not cause an increased rate of phagocytosis by monocytes/macrophages compared to normally deformable erythrocytes in our in vitro model. This suggests that the preferential removal of rigid cells in vivo is probably not a specific process, but is due to the increased splenic transit time of rigid erythrocytes and hence longer interaction time between erythrocytes and phagocytes.

Cells, Cultured↗

PubMed1975

Alteration of human erythrocyte membrane properties by complement fixation.

Erythrocyte survival studies of complement-coated radiolabeled erythrocytes have shown rapid removal of these cells from the peripheral blood with a return of these cells into the circulation within a few hours. We studied complement-coated human erythrocytes and measured surface charge and deformability, two parameters believed to be important in erythrocyte survival. Erythrocytes were coated with complement by two in vitro techniques: the addition of (a) low ionic strength sucrose, and (b) IgM cold agglutinins. Erythrocytes obtained from three patients with cold agglutinin disease were used as a source of in vivo complement-coated cells. No difference was found in surface charge as measured by electrophoretic mobility between erythrocytes from normal subjects and complement-coated erythrocytes from any of the three sources. When deformability was measured by filtration through 3-mum polycarbonate sieves, marked decreases in deformability were found in complement-coated erythrocytes. The filtration returned toward control levels by incubating the complement-coated erythrocytes in serum for 1 h and correlated with decreases in immune adherence. Using screen filtration pressure as a measure of deformability, a positive correlation between number of C3 molecules per erythrocyte and decreased deformability was found. C3b appeared responsible for the decreased deformability of the erythrocytes, since conversion of C3b to C3d resulted in a return of deformability toward normal. The data suggested that the sequestration of complement-coated human erythrocytes in the microvasculature can be explained in part by decreased deformability and changes in immune adherence.

Agglutinins↗

PubMed1992

Serological and biochemical studies on En(a-) human erythrocytes in a Japanese family.

The propositus erythrocytes with phenotype En(a-), which was found in the first example of a Japanese family, reacted with anti-N serum weaker than the ordinary phenotype N erythrocytes. When the erythrocyte membranes of the propositus were subjected to SDS-PAGE, no glycophorin A was observed on the gel by PAS staining, whereas glycophorin B band was observed. The S and the s antigens of the propositus erythrocytes were appeared to be normal. These results suggested that N activity of the propositus erythrocytes may be derived from glycophorin B components on the erythrocyte membranes. The amounts of bound sialic acid of the erythrocyte membranes were significantly lower in the En(a-) erythrocytes than the ordinary OMN erythrocytes. Neither the OMN nor the En(a-) erythrocytes showed the agglutinability to Arachis hypogaea lectin. The number of lectin receptor sites on the En(a-) erythrocyte membranes was significantly lower than on the OMN erythrocyte membranes for Limulus polyphemus, Triticum vurgaris and Bauhinia purpurea lectins. These results provide further support for the contention that En(a-) cells lack the glycophorin A as major erythrocytes sialoglycoprotein on the membranes.

Asian People↗

PubMed1983

Structural alteration of the erythrocyte membrane during malarial parasite invasion and intraerythrocytic development.

Erythrocyte entry by malarial merozoites causes structural alteration of the erythrocyte membrane. First, entry into erythrocytes by merozoites requires the formation of a junction between the erythrocyte membrane and the apical end of the merozoite. Secondly, migration of the junction parallel to the long axis of the merozoite brings the merozoite into an invagination of the erythrocyte membrane. Freeze-fracture studies show that the junction consists of a narrow band of rhomboidally arrayed intramembrane particles (IMP) on the P face of the erythrocyte membrane and matching rhomboidally arrayed pits on the E face. IMP on the P face of the erythrocyte membrane disappear beyond this junction, resulting in the absence of IMP from the P face of the parasitophorous vacuole membrane which originated from the erythrocyte membrane. The erythrocyte membrane is sealed off by fusion of the junction at the posterior end of the merozoite in the fashion of an iris diaphragm. After completing its entry into the erythrocyte the merozoite is surrounded by a parasitophorous vacuole membrane which is different in its molecular organization from the original erythrocyte membrane. In addition, two types of erythrocyte membrane modification are induced by intraerythrocytic parasites. They include electron-dense protrusions called knobs and caveola-vesicle complexes along the erythrocyte membrane.

Animals↗

PubMed1991

Maintenance and mobility of hemoglobin and water within the human erythrocyte after detergent disruption of the plasma membrane.

Is an intact plasma membrane responsible for keeping hemoglobin and water within the human erythrocyte? If not, what is responsible? How free is Hb to move about within the erythrocyte? To answer these questions erythrocytes were taken for phase contrast microscopy, transmission electron microscopy (TEM), determination of water-holding capacity, and proton NMR studies both before and after membrane disruption with a nonionic detergent (Brij 58). Addition of 0.2% Brij to a D2O saline solution of hemoglobin (Hb) caused particles of Hb to appear and to aggregate. This aggregation of Hb caused the amplitude of the Hb proton NMR spectra to decrease. Thus, the less mobile the Hb the lower the Hb proton spectra amplitude. Erythrocytes washed in D2O saline showed proton NMR spectra of relatively low amplitude. Addition of Brij (0.2%) to these erythrocytes caused increased Hb mobility within these erythrocytes. The TEM of fixed and thin-sectioned erythrocytes treated with Brij showed disruption of the plasma membrane of all erythrocytes regardless of whether or not they had lost Hb. Brij-permeabilized erythrocytes washed in D2O saline or in a D2O K buffer maintained a higher heavy water-holding capacity upon centrifugation as compared to nonpermeabilized erythrocytes. The TEM of Brij-treated and washed erythrocyte "shells" revealed a continuous submembrane lamina but no other evidence of cytoskeletal elements. The water-holding capacity of the erythrocyte can be accounted for by the water-holding capacity of hemoglobin. The evidence favors a relatively immobile state of Hb and of water in the erythrocyte that is not immediately dependent on an intact plasma membrane but is attributed to interactions between Hb molecules and the submembrane lamina.

Body Water↗

PubMed2001

Familial phosphofructokinase deficiency is associated with a disturbed calcium homeostasis in erythrocytes.

OBJECTIVES: To critically evaluate whether an altered calcium homeostasis in erythrocytes could be contributing to the symptomatology of the Tarui's disease, which is an inherited phosphofructokinase (PFK) deficiency of the muscle isoenzyme. PFK is a tetrameric enzyme with three different isoenzymes, muscle (M), liver (L), and platelet (P). Erythrocytes contain a 50 : 50 hybrid of M and L type. The deficiency of the muscle isoenzyme displays a symptomatology which is mainly characterized by myopathy, and a compensated haemolytic anaemia. DESIGN: Erythrocyte deformability was assessed before and after autoincubation. Energy related metabolites and energy charge was determined in erythrocytes under various experimental conditions. SETTING: The clinical part of the study was performed at the Departments of Cardiology and Clinical Chemistry, Umeå University Hospital, and the experimental investigation was carried out at the Department of Clinical Chemistry of the University Hospital of Uppsala, Sweden. SUBJECTS: Four family members with Tarui's disease participated in the study: the proband (patient 1), a 39-year-old male and two siblings, patient 2 (male, aged 46 years) and patient 3 (female, 30 years). Patient 4 (male, 16 years) was the son of the patient 2. Five healthy persons served as controls (controls 1-5). INTERVENTIONS: None. MAIN OUTCOME MEASURES: Cell-physiological variables were determined after autoincubation of erythrocytes (i.e. incubation in their own plasma at 37 degrees C) and after incubation in a composite buffered medium. RESULTS: Erythrocyte deformability as assessed by the erythrocyte fluidity was substantially decreased in patients compared to the moderate decrease in the control after 24 h of autoincubation, in presence of endogenous Ca2+ (heparin plasma). Moreover, autoincubation of erythrocytes shows that the patient's erythrocytes, although being moderately deficient in PFK activity, exhibit a normal (or slightly increased) lactate production compared to controls. Despite this, we show an increased ATP turnover with an Ca2+-induced AMP deaminase (and 5'-nucleotidase) activation leading to an increase in hypoxanthine content in patients' erythrocytes of about 100% after 24 h of autoincubation in heparin plasma, when compared to controls. A loss of volume in patient's erythrocytes after 24 h of autoincubation (in presence of Ca2+), as revealed by a diminished MCV, was consistent with an increased metabolic pool of intracellular calcium ions with a selective loss of K+ due to the activation of the K+ channel by intracellular Ca2+ (Gardos-effect). CONCLUSION: We conclude that the different calcium ion-induced effects on energy metabolism, structure and function of patients' erythrocytes are due to an augmented membrane leakage of Ca2+ and therefore an accumulated intracellular Ca2+ pool. This will result in an increased energy demand by the Ca2+-stimulated ATPase (calcium pump) to compensate for the dissipated Ca2+ gradient across the plasma membrane. The concomitant haemolysis may be explained by a diminished erythrocyte deformability due to Ca2+ overload.

Adolescent↗

PubMed1983

Paroxysmal nocturnal hemoglobinuria: deficiency in factor H-like functions of the abnormal erythrocytes.

Erythrocytes from patients with paroxysmal nocturnal hemoglobinuria (PNH) contained a subpopulation that lacked membrane-associated Factor H-like activity present on normal human erythrocytes. Initial deposition of C3b on the erythrocytes was effected using a fluid phase C3 convertase. The cells were then treated with fluorescein-labeled C3 and the cell-bound C3 convertase. Analysis utilizing the fluorescence-activated cell sorter revealed two distinct cell populations, one of which was highly fluorescent, indicating a large number of C3b molecules per cell. Only this population (43%) was susceptible to lysis (44%) when exposed to acidified serum before C3b deposition. The less fluorescent population resembled normal human erythrocytes and was not affected by prior treatment with acidified serum. Since C3b deposition occurred almost exclusively on the complement-sensitive cells in the PNH erythrocyte population, these cells could be examined for the Factor H-like regulatory activities without prior isolation. These functions include enhancement of inactivation of erythrocyte-bound C3b by Factor I and acceleration of the decay of erythrocyte-bound C3 convertase, C3b,Bb. It was found that C3b on PNH erythrocytes was 100-fold less susceptible to inactivation by Factor I than C3b on normal human erythrocytes. The half-life at 22 degrees C of C3b,Bb on PNH erythrocytes was threefold greater than on normal human erythrocytes and similar to that of the enzyme bound to particles that do not possess Factor H-like activity. These observations suggest that the abnormal susceptibility of PNH erythrocytes to lysis by complement is due to a functional deficiency in one or more of the Factor H-like proteins present on normal human erythrocytes.

Complement C3↗

PubMed1978

Electron spin resonance studies of erythrocytes from patients with Duchenne muscular dystrophy.

The membrane organization of the erythrocytes from patients with Duchenne muscular dystrophy was studied by means of electron spin resonance. The fluidity of the membrane near the polar region of Duchenne muscular dystrophy erythrocytes was similar to that of normal erythrocytes. The membrane environment in the nonpolar region, however, was quite different from that of normal erythrocytes, judged by the spectra with 2-(14-carboxytetradecyl) - 2 - ethyl - 4,4 - dimethyl - 3 - oxazolidinyloxyl as probe. The temperature dependence of the ratio of the line height of central field to that at the low field showed two inflection points in normal erythrocytes at pH 7.4 (13.5 degrees -16.5 degrees and 37.5 degrees -40.5 degrees C, respectively) but the inflection point in the lower temperature range was not detected in Duchenne muscular dystrophy erythrocytes. When pH was varied, an abrupt decrease in the ratio was observed at pH 5.9-5.6 in normal erythrocytes whereas there was a gradual decrease over the range of pH from 6.6 to 5.0 in Duchenne muscular dystrophy erythrocytes. The rate of reduction of the radical 2-(3-carboxypropyl)-4,4-dimethyl-2-tridecyl-3-oxazolidinyloxyl by ascorbate in normal erythrocytes was faster than that in Duchenne muscular dystrophy erythrocytes. Treatment of both erythrocytes with phloretin markedly reduced the rate of reduction by ascorbate and eliminated the difference in the two types of erythrocyte. These results indicate that in Duchenne muscular dystrophy the erythrocyte membrane is involved as well as the muscle cell.

Adolescent↗

PubMed1983

Oxidant damage of the lipids and proteins of the erythrocyte membranes in unstable hemoglobin disease. Evidence for the role of lipid peroxidation.

Since unstable hemoglobins have been considered a source of reactive oxygen radicals, and oxidative membrane damage a prehemolytic event, we examined the erythrocyte membranes of six patients (three splenectomized) with hemoglobin Köln disease. In the hydrogen peroxide stress test, the patients' erythrocytes generated more than twice the malonyldialdehyde (a lipid peroxidative product) than control erythrocytes. Fluorescence spectra of lipid extracts of the patients' erythrocytes showed an excitation maximum at 400 nm and an emission maximum of 460 nm, characteristic of malonyldialdehyde lipid adducts. Two types of membrane polypeptide aggregates were found in the erythrocytes of the splenectomized patients. The first, which were dissociable by treatment with mercaptoethanol, contained disulfide-linked spectrin, band 3 and globin. The second, not dissociable by mercaptoethanol, had an amino acid composition similar to that of erythrocyte membranes and spectrin (unlike globin) and like that of aggregates produced by the action of malonyldialdehyde on normal erythrocyte membranes. Atomic absorption spectroscopy of hemoglobin Köln erythrocytes showed no increase in calcium content implying that these cross-links were not due to calcium-stimulated transglutaminase. Using a micropipette technique, we demonstrated that erythrocytes containing membrane aggregates from splenectomized patients were less deformable while aggregate-free erythrocytes from non-splenectomized patients had normal deformability. We conclude that the erythrocyte membranes in hemoglobin Köln disease show evidence of lipid peroxidation with production of malonyldialdehyde, and that the nondissociable membrane aggregates formed in this disease are likely cross-linked by malonyldialdehyde. Because the erythrocytes containing membrane aggregates from splenectomized patients with unstable hemoglobin disease show decreased membrane deformability, we hypothesize that this abnormality results in premature erythrocyte destruction in vivo.

Blood Proteins↗

PubMed1998

Cell age distribution of erythrocytes at the incidence of cerebral stroke in stroke-prone spontaneously hypertensive rats, and their glutathione peroxidase activity.

To study the mechanism of the fall of glutathione peroxidase (GSH-Px) activity in erythrocyte after cerebral strokes in stroke-prone spontaneously hypertensive rats (SHRSP), erythrocytes were fractionated into low density erythrocytes (LD-E) and high density erythrocytes (HD-E) by a density gradient centrifugal method using Percoll solution, and fluctuation of the distribution ratio and changes of GSH-Px activity in fractionated erythrocytes were investigated. The distribution ratio of LD-E and HD-E in erythrocytes of SHRSP was about 4:1 at 5 weeks of age (n = 6), and the distribution to HD-E increased along with aging. While the distribution ratio was changed, however, there was no change in the GSH-Px activity in both LD-E and HD-E of erythrocytes. In senile, 30-week-old SHRSP (n = 4) with advanced hypertension, the GSH-Px activity in the HD-E was lower, in proportion to the increase of the distribution rate against HD-E. On the other hand, in SHRSP (n = 5) having cerebral stroke, the distribution ratio of LD-E and HD-E was about 1:4. The GSH-Px activity was 31.4 +/- 2.9 units/10(10) erythrocytes in LD-E, which was hardly different from the value of SHRSP without stroke (35.7 +/- 3.3 units/10(10) erythrocytes). In HD-E, however, the activity was 18.2 +/- 2.2 units/10(10) erythrocytes, being lower than the activity of SHRSP without stroke. At the moment when the GSH-Px activity had dropped to 17 units/mg hemoglobin, and the control diet was changed to one based on fish or a hydralazine treatment given, the activity recovered, and an increase in body weight and the distribution rate of the LD-E over HD-E was increased. It is clear from these experiments that the fall of erythrocyte GSH-Px activity observed after cerebral stroke is due to a decrease of LD-E and increase of HD-E, which has lowered activity. However, nothing definite is known on the relationship between the fall of GSH-Px activity in erythrocytes and disorder in cerebral tissue. It appears that the fall of the GSH-Px activity causes at least functional and structural changes in erythrocytes, which interfere with the delivery of oxygen to peripheral tissues, triggering oxidation stress in cerebral tissues.

Animals↗

PubMed1988

Effect of statil (ICI 128436) on erythrocyte viscosity in vitro.

The hypothesis that sorbitol accumulation could contribute to a reduced erythrocyte deformability in diabetes was investigated. Erythrocyte sorbitol and erythrocyte viscosity at high and low shear rates were studied in 20 insulin-dependent diabetic (IDDM) and 20 matched control subjects. An increased erythrocyte sorbitol and an increased low-shear erythrocyte viscosity were found in the IDDM patients, but there was no significant correlation (r = .11, NS) between the parameters. Incubation (3 h, 37 degrees C) in a Krebs buffer containing 33.3 mM glucose resulted in a significant sorbitol accumulation, but erythrocyte viscosity was not affected. Despite this fact, addition of 1 mM statil (ICI 128436) in the 5.5- and 33.3-mM glucose media not only prevented erythrocyte sorbitol accumulation but also improved erythrocyte viscosity in diabetic and control subjects. The effect was more pronounced at the low (approximately 16%) than at the high (approximately 2%) shear rate. The effect on erythrocyte viscosity disappeared by washing the erythrocytes after incubation, although erythrocyte sorbitol remained different. Our results suggest that sorbitol accumulation does not contribute to an increased erythrocyte viscosity in diabetes, and statil shows a positive effect on erythrocyte viscosity independent of its aldose reductase-inhibiting property.

Adult↗

PubMed1993

Recognition and sequestration of young and old erythrocytes from young and elderly human donors: in vitro studies.

Experiments were performed to determine the mechanism of recognition for sequestration of erythrocytes from elderly and young donors and to study in vitro a previously observed shortening of in vivo life span of erythrocytes in elderly donors. Erythrocytes from young and elderly human donors were separated according to their age-density on Stractan gradients. Elderly donors had more low age-density erythrocytes than did young donors. Erythrocytes from elderly donors had higher levels of immunoglobulin G (IgG) on their erythrocytes than did those from young donors. In an in vitro erythrophagocytosis assay, young (low age-density) and old (high age-density) erythrocytes from elderly donors and old but not young erythrocytes from young donors were recognized and sequestered. Phagocytosis of erythrocytes from elderly and young donors can be specifically blocked by beta-galactoside but not alpha-galactoside sugars. This phagocytosis is not blocked by protein G, which specifically blocks Fc-gamma-mediated erythrophagocytosis, thus demonstrating that the recognition of the senescent erythrocyte is not due to the direct recognition of a physiologic autoantibody. beta-Galactoside and alpha-galactoside sugars have no inhibitory effect on erythrophagocytosis mediated by IgG anti-Rh-D antibodies. Erythrophagocytosis of young and old erythrocytes from elderly donors and old erythrocytes from young donors are all mediated by a macrophage receptor with lectin-like properties, which can be inhibited by a beta-galactoside-like sugar moiety, and not by an Fc receptor that recognizes erythrocyte-bound IgG.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1996

Poly-N-acetyllactosaminyl saccharide chains of band 3 as determinants for anti-band 3 autoantibody binding to senescent and oxidized erythrocytes.

Natural IgG antibodies to band 3 glycoprotein of erythrocyte membrane (anti-band 3 IgG) are known to bind to senescent erythrocytes, and believed to initiate antibody-dependent phagocytic removal of the senescent cells from blood circulation. Anti-band 3 antibodies also bind to the erythrocytes with hereditary hemoglobin abnormalities such as sickle, beta-thalassemic and hemoglobin Köln erythrocytes. Oxidative stress appears to be responsible for the generation of senescent cell antigen on erythrocytes, to which anti-band 3 antibodies bind, since erythrocytes oxidized in vitro bind anti-band 3 IgG, and various oxidative modifications are observed in senescent erythrocytes as well as the erythrocytes with abnormal hemoglobin. Major antigenic sites of band 3 for anti-band 3 IgG autoantibodies are its sialylated poly-N-acetyllactosaminyl saccharide chains. The poly-N-acetyllactosaminyl saccharide chains on senescent erythrocytes are indeed involved in the antigenic sites on senescent erythrocytes. The finding of the carbohydrate epitopes and possible involvement of oxidative mechanism are compatible with the band 3 clustering hypothesis, in which clustering of band 3 molecules in erythrocyte membrane is supposed to be responsible for effective binding of anti-band 3 IgG to the cell surface, because the carbohydrate epitopes of band 3 can form multivalent epitopes on cell surface when band 3 molecules cluster, and oxidative stress can induce such clusters. Interestingly, poly-N-acetyllactosaminyl chains of band 3 on oxidized erythrocytes are also recognized by macrophages directly. Thus, poly-N-acetyllactosaminyl chains may play dual roles as determinants for recognition by anti-band 3 IgG and by macrophages.

Anion Exchange Protein 1, Erythrocyte↗

PubMed1992

Functional characterization of non-human primate erythrocyte immune adherence receptors: implications for the uptake of immune complexes by the cells of the mononuclear phagocytic system.

Erythrocytes from primates express an immune adherence (IA) receptor that binds complement-opsonized immune complexes (IC) both in vivo and in vitro. We have analyzed the immunochemical and functional properties of the IA receptor from erythrocytes from species that have been used for in vivo IC clearance studies and have compared these properties to the human IA receptor (which is called complement receptor type 1, CR1). Erythrocytes from all species (chimpanzee, baboon, rhesus and cynomolgus monkey) bind antibody/double-stranded DNA IC when opsonized with autologous complement. However, IC which are bound to chimpanzee erythrocytes are not released upon addition of chimpanzee serum (which contains factor I activity), while IC bound to baboon erythrocytes and human erythrocytes are released upon addition of autologous serum. Anti-human CR1 monoclonal antibodies (mAb) E11 and HB8592 bind to erythrocytes from all species examined and the number of mAb epitopes per erythrocyte correlated with the number of IC that could bind to the erythrocyte under saturating conditions. However, a number of interesting differences between the species are observed with other mAb. The anti-CR1 mAb 1B4 and 3D9, which block recognition of ligand by CR1, did not bind to chimpanzee erythrocytes and bound partially to rhesus and cynomolgus monkey erythrocytes. In addition, the ability of autologous serum to induce release of erythrocyte-bound IC correlates with the presence of these epitopes. These findings, taken in context with previous clearance studies, suggest that serum-mediated release may not be required for the rapid transfer of the IC from the erythrocyte to the mononuclear phagocytic system.

Animals↗

PubMed1995

Cholesterol modulation of transmembrane cation transport systems in human erythrocytes.

The aim of this study was to investigate whether in vitro cholesterol enrichment of human erythrocytes affects transmembrane cation transport systems by changes induced in the membrane microviscosity of these cells. Human erythrocytes in suspension were incubated with cholesterol-lecithin dispersions to obtain an enrichment of their membrane cholesterol. The ouabain-sensitive Na+ efflux, the Na+, Li+(-)countertransport activity, the Na+, K+(-)cotransport activity, the basal transmembrane leakage of Na+ and K+, and the enzymatic activity of ATPases were determined in these cholesterol-rich cells and compared with control cells. Membrane core and surface microviscosity was also measured in the control and cholesterol-enriched cells, using the fluorescent probes, 1,6-diphenyl-1,3,5-hexatriene (DPH) and trimethylammonium (TMA)-DPH, respectively. The cholesterol content of the erythrocytes incubated in the presence of cholesterol-rich dispersions increased gradually over time. A 47% increase membrane cholesterol content was obtained after 16 h of incubation, while no change in the erythrocyte phospholipid content was found. High membrane cholesterol in the human erythrocyte phospholipid content was found. High membrane cholesterol in the human erythrocyte, obtained by in vitro enrichment of the cells with cholesterol-lecithin dispersion, inhibited in intact cell suspensions the ouabain-sensitive Na+ efflux, an estimate of the Na+(-)pump activity, and in isolated erythrocyte membranes the enzymatic activity of Na+, K+(-)ATPase, and Mg2+(-)ATPase. The dissociation constant for internal sodium and the maximal rate of ouabain-sensitive Na+ efflux is decreased in cholesterol-rich erythrocytes compared to control cells. The elevated erythrocyte membrane cholesterol content was also accompanied by a decrease in the Na+,K+(-)cotransport activity, the Na+, Li+(-)countertransport activity, and the transmembrane basal leakage of Na+ and K+. Microviscosity, measured in the erythrocyte membrane core with the fluorescence probe DPH, was increased in the cholesterol-rich cells compared to the control cells. However, the membrane surface microviscosity, measured with the probe TMA-DPH, was not different between the control cell and the cholesterol-rich cells. The present data show that enrichment of the human erythrocyte membrane with cholesterol results in an increase of membrane core microviscosity, resulting in an inhibition of transmembrane cation transport systems in erythrocytes in suspensions and of erythrocyte membrane Na+,K+(-)ATPase, Ca2+(-)ATPase, and Mg2+(-)ATPase.

Adenosine Triphosphatases↗