Red cell agglutination kinetics: a method for automatic recording with the fragiligraph

Caffeine activates a mechanosensitive Ca(2+) channel in human red cells

Caffeine is known to activate influx of both mono- and divalent cations in various cell types, suggesting that this xanthine opens non-selective cation channels at the plasma membrane. This possibility was investigated in human erythrocytes, studying the caffeine action on net Ca(2+), Na(+) and K(+) movements in ATP-depleted cells. Whole populations and subpopulations of young and old erythrocytes were employed. Caffeine was tested in the presence of known mechanosensitive channel blockers (Gd(3+), neomycin and amiloride) and ruthenium red as a possible inhibitor. Caffeine enhanced net cation fluxes in a concentration-dependent way. In whole populations, the Ca(2+) entry elicited by 20 mM caffeine was fully suppressed by Gd(3+) (5 microM), amiloride (250 microM) and ruthenium red (100 microM) and partially blocked by neomycin (100 microM). The above blockers also inhibited caffeine-dependent Na(+) entry whilst showing antagonistic effects on the corresponding K(+) efflux. These compounds fully suppressed hypotonically-induced (-35 mOsm/kg) Ca(2+) influx at nearly the same concentrations completely blocking caffeine-stimulated Ca(2+) entry. The effect of inhibitors on Ca(2+) influx in young cells exceeded that in old cells at similar concentrations. The results clearly show that caffeine stimulates a stretch-activated Ca(2+) channel in human red cells and that aged cells are less susceptible to mechanosensitive channel blockers.

Reduced CR1 expression on aged human erythrocytes: immuno-electron microscopic and functional analysis

Recognition and clearance of aged human erythrocytes (AE) is a complex process involving immune and non-immune reactions. Complement activation on the surface of AE and deposition of the C3b complement component appear to facilitate this process. Complement receptor type 1 (CR1, CD35) expressed on the surface of human erythrocytes binds to C3b molecules and promotes their inactivation by complement factor I. This may protect the erythrocytes from lysis by complement and by phagocytes. It has been previously reported that aging of human erythrocytes is accompanied by a decrease in the number of CR1 molecules expressed on their surface. Results presented here further support this finding with for the first time a presentation of immune-electron microscopic observation. Haemagglutination and binding assays showed that AE express significantly fewer CR1 (CD35) molecules than young erythrocytes (YE). This is associated in AE with reduced CR1-like factor I co-factor activity and increased deposition in vivo of C3, C4 and properdin as well as increased sensitivity to lysis in vitro by homologous and heterologous complement. Three different immuno-electron microscopical techniques have been used to clearly show the quantitative difference in CR1 (CD35) expression between AE and YE. Finally our results demonstrate that the previously reported clustered arrangement of CR1 (CD35) on human erythrocytes is similar on aged and young erythrocytes.

Variations in surface charge distribution of leukemic and non-leukemic transformed cells

The surface negative charge distribution of fresh leukemic cells from patients with acute leukemia was examined with cationized ferritin (CF), an electron dense label of anionic sites and compared with leukemic cells from phase-cycle fractionated populations of a human leukemic cell line K-562. Normal-untreated and phytohemagglutinin (PHA)-transformed lymphocytes were also tested. A CF-induced redistribution of anionic sites into clusters and patches within a wide range of variations in density was observed electron microscopically both in fresh acute leukemic cells and in unseparated cells of the K-562 line. Cells of the G0/G1 fraction from a phase-cycle separated K-562 population exhibit a higher density of CF label per unit length of membrane as compared with the G2 + M cell fraction. PHA-benign transformed normal lymphocytes exhibit an even and continuous CF labeling, similar to that of normal-untreated lymphocytes. An attempt was made to correlate the CF-induced charge redistribution with the rate of agglutination with the cationic Poly-L-lysine. Our observations indicate that the CF ligand does induce an anionic site redistribution, varying in density, both in fresh leukemic cells and in cells from a K-562 line, and does not in normal untreated and PHA-benign transformed lymphocytes. The particular pattern of anionic site redistribution observed in leukemic cells of this study is apparently phase-cycle dependent.

Ethanol-induced alterations in human erythrocyte shape and surface properties: modulatory role of prostaglandin E1

Exposure of human erythrocytes to ethanol (1 to 20% by vol) in Ca2+ and Mg2+-free phosphate-buffered saline, pH 7.4, transformed biconcave discs into spiculated echinocytes within 3 min at 25 degrees C. The effects of ethanol were concentration-and time-dependent, but reversible by washing in the incubation buffer system within 60 min of initial exposure to ethanol. After prolonged ethanol exposure (180 min), washing of cells resulted in the formation of stomatocytes (cup-forms). Ethanol-induced echinocytosis was also accompanied by a 30% enhancement in the agglutinability of erythrocytes by ligands with high affinity for negative surface charge (poly-L-lysine and wheat germ agglutinin, 20 microliters/ml) without any alterations in surface charge topography. Concomitant exposure of erythrocytes to prostaglandin E1 (100 nM) selectively prevented the enhancement of ligand-mediated agglutinability, but did not modify cell shape. These data indicate that certain erythrocyte surface properties may not be directly influenced by cell shape and suggest a unique modulatory action of prostaglandin E1 on shape-transformed cells.

The relationship between sialic acid content and peanut agglutinin binding on senescent and enzyme treated human erythrocytes

Young, old and neuraminidase treated human red blood cells (RBC) were investigated with peanut agglutinin (PNA), a lectin with a specificity similar to that of serum T-agglutinin. The effect of serum agglutinins on this interaction was also investigated. The density and distribution of PNA receptors were evaluated by agglutination with PNA and binding of ferritin-conjugated PNA (PNA-F), or PNA labeled with radioactive iodine [( 131I] PNA). The results were correlated with the distribution of membrane bound sialic acids, as evaluated by chemical analysis and rate of agglutination with poly-L-lysine (PLL). Untreated RBC of all ages did not agglutinate with PNA and failed to bind PNA-F and [131I] PNA. Treatment of young RBC with neuraminidase, which resulted in reduction of membrane-bound sialic acids to an extent similar to that of physiologically aged RBC, resulted in the concomitant exposure of PNA binding sites and in the agglutination of these cells by autologous serum. Pretreatment of the neuraminidase treated RBC with autologous serum resulted in partial inhibition of the binding capacity of PNA on the RBC. The results indicate that the normal age-related loss of sialic acids in circulating RBC is not identical with enzymatic removal of sialic acids by neuraminidase. The observations suggest that different mechanisms are functional in the recognition and sequestration of old RBC and of RBC treated with neuraminidase.

Hydrophobic chromatography of cells: adsorption and resolution on homologous series of alkylagaroses

Implantation of hydrocarbon chains on beaded agarose results in column materials capable of adsorbing erythrocytes or lymphocytes from various sources. In a homologous series of such columns, identical in all structural respects (ligand density, charge density and ultrastructure) except for the length of their hydrocarbon chains, the capacity to adsorb these cells generally increases with increase in the number of carbon atoms per chain. The cells can be desorbed from the columns by repeated gentle pipetting in the presence of bovine serum albumin (for erythrocytes) or foetal calf serum (for lymphocytes). Under the conditions used for adsorption and desorption there is neither physical entrapment of the cells in the column nor apparent damage to their integrity, as indicated by the facts that (a) 95-98% of the cells applied on the column can be recovered; (b) erythrocytes eluted from the column and those yet to be applied are morphologically indistinguishable, exhibit an identical osmotic fragility profile and, (after desorption) retain the same adsorption profile for the columns; and (c) over 95% of the mouse spleen lymphocytes, eluted from the columns, continue to exclude the dye Trypan blue, suggesting that they preserve their viability. Cells from different sources exhibit different adsorption profiles on homologous series of alkylagaroses, allowing the detection of differences in the surface of these cells and their resolution by these columns. Exploratory experiments with artificial cell mixtures are described, illustrating the possibility of enriching the mixture with one of the cell types by preferential adsorption or exclusion on an appropriate alkylagarose. The best resolution was obtained with a mixture of erythrocytes and spleen lymphocytes (both from DBA/1 mice). After appropriate "tailoring" of the column material used (an ethylagarose) it was possible to apply a 1:1 mixture of these cells and to obtain (after preferential adsorption) essentially pure erythrocytes (98% of the excluded cells).(ABSTRACT TRUNCATED AT 400 WORDS)

Expression of peanut agglutinin receptors on virus-induced preleukemic cells in mice

Preleukemic bone marrow and spleen cells of irradiated C57BL/6 mice that were inoculated with the radiation-induced leukemia virus variant D-RadLV differ from autonomous end-stage leukemia cells in the expression of the receptor for peanut agglutinin. As a result, the preleukemic cells are agglutinated by peanut agglutinin and the end-stage cells are not. This observation provides further evidence that preleukemic cells possess surface markers similar to those of the prothymocyte. In vitro and in vivo thymocyte-virus interactions reveal that cells susceptible to D-RadLV transformation are present mainly among the peanut agglutinin-receptor-bearing thymocyte population which has previously been demonstrated to be immunologically immature.

Phagocytosis of nucleated and mature beta thalassaemic red blood cells by mouse macrophages in vitro

Physiological or experimental decrease in sialic acid (SA) content on the red blood cell (RBC) membrane is believed to play an important role in the recognition of these cells by macrophages. Since there is a 20-30% decrease in the SA content on the membrane of thalassaemic RBC, the interaction between macrophages and these RBC was studied in vitro. Using mouse peritoneal macrophages, it was found that these macrophages 'recognize' and phagocytize thalassaemic RBC while RBC from normal donors are hardly phagocytized. The average level of phagocytosis of thalassaemic RBC from splenectomized patients was found to be 22-fold higher than that of RBC from normal donors. The phagocytized cells consisted of both mature and nucleated RBC. Mouse peritoneal macrophages seem to be a useful in vitro system for the study of the accelerated sequestration and shortened life span of thalassaemic RBC.

Rabbit erythrocyte survival following diminished sialic acid and ATP depletion

The limited deformability and ATP depletion was considered by some authors to be the factor limiting the life span of old red blood cells (RBC) in circulation. Others believed that sialic acid on the RBC surface determines their life span. We compared the life span of 51Cr labelled, neuraminidase treated rabbit RBCs with ATP depleted by incubation at 37 degree C rabbit RBCs. Osmotic fragility, agglutinability, glucose-6-phosphate dehydrogenase (G6PD) and hexokinase activity and ATP levels of these cells were determined. Desyalated RBCs were removed from the circulation within 24 hours. ATP levels, G6d and hexokinase activity and osmotic fragility were normal in these cells. The agglutination by poly(L-lysine) was affected by the loss of surface charge on these cells. Half the ATP depleted RBCs were out of the circulation within three days. Reconstitution of ATP by reincubation with adenosine, elevated the ATP levels to about 80% of their original level, but survival of these cells did not improve. Analysis of sialic acid showed tha 50% of it was removed during the incubation for ATP depletion. The low ATP level and loss of sialic acid fromt he RBC membrane appeared to be conincidental rather than dependent on each other. The latter appears to be a primary factor in red cell survival.

Detection of anti-red blood cell antibodies by treatment of the cells with neuraminidase

Neuraminidase treated RBC were used to detect incomplete unbound anti RBC antibodies in the plasma of patients with immune diseases. 80% (48 out of 60) of the examined patients gave positive results with this method while all the 50 normal controls were negative. The indirect antiglobulin test was negative in all the patients. In the direct antiglobulin test only two RBC samples, whether treated with neuraminidase or not, gave positive results. The present study indicates that the assay of plasma on neuraminidase treated RBC may serve as a sensitive method for the detection of the presence of anti RBC antibodies in various immunological diseases.

A method for automatic recording of serum lysozyme activity with the fragiligraph

A quick and simple method for the estimation of lysozyme activity using the Fragiligraph, was described. Diminution of turbidity in a suspension of Micrococcus lysodeikticus produced by the addition of standard lysozyme (hen egg white) or serum sample, was continuously recorded for 5 min by the Fragiligraph. The normal mean serum lysozyme activity value obtained by this method is 6,80 mug/ml +/- 1.85.

Electron microscope analysis of young and old red blood cells stained with colloidal iron for surface charge evaluation

Human and rabbit red blood cells, separated into "young" and "old" age groups by differential flotation on phthalate esters, were fixed with glutaraldehyde and labeled with colloidal ferric oxide. Electron micrographs of thin sections of young cells showed a uniform and dense depostion of positive iron particles. Old cells showed particles deposited irregularly, leaving unlabeled gaps on the membrane surface. Red cells incubated with 10 units/ml receptor-destroying enzyme (RDE) demonstrate a reduced labeling, similar to that of old cells. After neuraminic acid had been removed from red cells by 20 units/ml RDE, no iron particles were found on membrane surfaces. The different labeling of young, old, and RDE-treated human and rabbit red cells was correlated with their electric mobility and agglutinability by poly-L-lysine. The contradiction between the apparent similarity in charge density of human and rabbit red cells as estimated by density of iron particles and the markedly lower electric mobility of rabbit red cells is discussed.