Immuno-electronmicroscopic study of human EA rosettes.

The immuno-electronmicroscopic study of human EA rosettes, using ferritin-labelled anti-human IgG antiserum, showed clusters of ferritin granules at the points of contact between erythrocytes and lymphoid cells, indicating that the links between Fc fragment of IgG on the surface of erythrocytes and specific receptor on the surface of lymphoid cell correspond to the sites of morphological interaction between the 2 cell types.     

K-Lymphocyte cytotoxicity: role of human blood group ABO, rhesus and P alloantibodies]

Using human erythrocytes of known antigenic density, sensitized by ABO and Rhesus (D) alloantibodies, it is shown that K cell cytotoxicity mediated by peripheral blood lymphocytes is directly correlated with the number of IgG molecules specifically bound to the target cell surface. The lytic sensitivity of P1k but not P2 or p erythrocytes coated with anti-Tja (anti-P + P1 + Pk) antibodies, demonstrates that effector K cells are mainly triggered through the IgG ANTI-Pk component of such sera.     

Incorporation of14C-thymidine by cultures of erythrocytes from rheumatoid arthritis patients and normal subjects,suggesting the presence of an L-form

Summary Cultures of washed erythrocytes from rheumatoid arthritis patients and normal subjects were found to incorporate¹⁴C-thymidine,suggesting the presence of an L-form. The extent of the incorporation by erythrocytes from rheumatoid patients was more variable than that by erythrocytes from normal subjects, and correlated negatively with IgG measurements and white cell counts performed on the patients' bloods, although not with the clinical activity of the patients.     

An increase in Sendai virus-induced cell fusion of erythrocytes infected with Plasmodium chabaudi

The extent of cell fusion induced by Sendai virus was examined in erythrocytes infected with Plasmodium chabaudi. An increase in cell fusion of erythrocytes with Ehrlich tumor cells and of erythrocytes with erythrocytes was observed with the infected erythrocytes. However, agglutination by the virus was not changed between erythrocytes of normal and malarial mice. These results indicate that the increase in cell fusion occurred in the process of membrane fusion, suggesting that some membrane property of Plasmodium-parasitized erythrocytes is changed in terms of Sendai virus-induced cell fusion.     

An increase in Sendai virus-induced cell fusion of erythrocytes infected withPlasmodium chabaudi

Summary The extent of cell fusion induced by Sendai virus was examined in erythrocytes infected withPlasmodium chabaudi. An increase in cell fusion of erythrocytes with Ehrlich tumor cells and of erythrocytes with erythrocytes was observed wit the infected erythrocytes. However, agglutination by the virus was not changed between erythrocytes of normal and malarial mice. These results indicate that the increase in cell fusion occurred in the process of membrane fusion, suggesting that some membrane property ofPlasmodium-parasitized erythrocytes is changed in terms of Sendai virus-induced cell fusion.We thank Drs George L. Gerton, T. Matsuyama and M. Niwa for their comments on this work and Mr I. Kimata for preparing photographs.     

Serological identification of an antigen associated with acute lymphoid leukemia]

Using as references a lymphoblastoid cell line established from the pleural effusion of a lymphosarcoma patient and the corresponding autochtonous reactive serum, absorption typing assays resulted in the identification of a cell surface antigen associated with acute lymphoid leukaemia. This antigen, provisionally termed PON, may also be demonstrated on the cells of some acute myelomonocytic leukaemias and lymphosarcomas.     

Suppression of the immune response by drugs interfering with the metabolism of serotonin

The work was based on the assumption that neurohumoral control of the immune response, particularly in stressed animals, involves central serotoninergic mechanisms. Rats immunized with sheep erythrocytes were stressed by repeated restraints and/or treated with a precursor of serotonin (5-hydroxytryptophan, 5-HTP) or with an inhibitor of serotonin synthesis (parachlorophenylalanine, PCPA). As expected, repeated stresses reduced the plaque-forming cell (PFC) response. Treatment with 5-HTP also reduced the PFC response, and potentiated the immunosuppressive effect of stress. This was accompanied by increased metabolism of serotonin in the brain, as indicated by increased concentration of its metabolite, 5-hydroxyindoleacetic acid (5-HIAA), in cerebral tissue. Treatment with PCPA also suppressed the PFC response, but this suppression was accompanied by decreased levels of brain serotonin and of 5-HIAA. Plasma corticosterone levels were elevated in rats treated with PCPA. It seems that putative central effects of PCPA on serotoninergic regulation of the immune response were outweighed by its effects on corticosterone secretion and/or on lymphoid cells.     

Suppression of the immune response by drugs interfering with the metabolism of serotonin

Summary The work was based on the assumption that neurohumoral control of the immune response, particularly in stressed animals, involves central serotoninergic mechanisms. Rats immunized with sheep erythrocytes were stressed by repeated restraints and/or treated with a precursor of serotonin (5-hydroxytryptophan, 5-HTP) or with an inhibitor of serotonin synthesis (parachlorophenylalanine, PCPA). As expected, repeated stresses reduced the plaque-forming cell (PFC) response. Treatment with 5-HTP also reduced the PFC response, and potentiated the immunosuppressive effect of stress. This was accompanied by increased metabolism of serotonin in the brain, as indicated by increased concentration of its metabolite, 5-hydroxyindoleacetic acid (5-HIAA), in cerebral tissue. Treatment with PCPA also suppressed the PFC response, but this suppression was accompanied by decreased levels of brain serotonin and of 5-HIAA. Plasma corticosterone levels were elevated in rats treated with PCPA. It seems that putative central effects of PCPA on serotoninergic regulation of the immune response were outweighed by its effects on corticosterone secretion and/or on lymphoid cells.     

IgM memory B cells: a mouse/human paradox

Humoral memory is maintained by two types of persistent cells, memory B cells and plasma cells, which have different phenotypes and functions. Long-lived plasma cells can survive for a lifespan within a complex niche in the bone marrow and provide continuous protective serum antibody levels. Memory B cells reside in secondary lymphoid organs, where they can be rapidly mobilized upon a new antigenic encounter. Surface IgG has long been taken as a surrogate marker for memory in the mouse. Recently, however, we have brought evidence for a long-lived IgM memory B cell population in the mouse, while we have also argued that, in humans, these same cells are not classical memory B cells but marginal zone (MZ) B cells which, as opposed to their mouse MZ counterpart, recirculate and carry a mutated B cell receptor. In this review, we will discuss these apparently paradoxical results.     

Direct inhibition of phospholipid scrambling activity in erythrocytes by potassium ions

The exposure of phosphatidylserine (PS) at the cell surface plays a critical role in blood coagulation and serves as a macrophage recognition moiety for the engulfment of apoptotic cells. Previous observations have shown that a high extracellular [K⁺] and selective K⁺ channel blockers inhibit PS exposure in platelets and erythrocytes. Here we show that the rate of PS exposure in erythrocytes decreases by ~50% when the intracellular [K⁺] increases from 0 to physiological concentrations. Using resealed erythrocyte membranes, we further show that lipid scrambling is inducible by raising the intracellular [Ca²⁺] and that K⁺ ions have a direct inhibitory effect on this process. Lipid scrambling in resealed ghosts occurs in the absence of cell shrinkage and microvesicle formation, processes that are generally attributed to Ca²⁺-induced lipid scrambling in intact erythrocytes. Thus, opening of Ca²⁺-sensitive K⁺ channels causes loss of intracellular K⁺ that results in reduced intrinsic inhibitory effect of these ions on scramblase activity. Received 11 September 2008; received after revision 17 October 2008; accepted 27 October 2008     

Detection of antigenic determinants of membranes using an insoluble peanut lectin]

The binding of lectins on insoluble supports may be used to detect the interactions occurring between these molecules and the sites of some receptors of membranes. An example is given, using the "anti-T" lectin extracted from peanut, to show the presence of determinants with terminal free glactose on the surface of erythrocytes and lymphocytes.     

Effekt der Perjodsäure auf die Erythrocytenmembran

Summary M/2 up to M/500 HJO₄ produces a very peculiar ductility of native erythrocyte membranes, whereas a similar effect is hardly observed on the membranes of trypsin-treated erythrocytes. This observation demonstrates indirectly, probably for the first time, the morphological existence of a loose protein-layer assumed by one of the authors to be present on the surface of erythrocytes.     

Die Rouleau-Bildung der Rindererythrocyten

Summary Not a trace of rouleau formation could be observed with native beef erythrocytes under varying conditions. A typical rouleau formation and a markedly increased sedimentation rate could, however, be elicited when the surface layer of the beef erythrocytes was carefully removed with proteolytic enzymes. This is an additional evidence that the beef erythrocytes are enveloped in a surface sheet, which inhibits their hemagglutination and their rouleau formation. Papain is a proteolytic enzyme, which is inactive regarding rouleau formation. Lysolecithin disintegrates the rouleaus, albumin restores them.

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Diese Arbeit wurde von der H.-Buss-Stiftung (Basel) unterstützt.     

Genome and cell sizes in frogs: A comparison with salamanders

Summary The nuclear volume (Nv), cell volume (Cv) and cell surface area (Cs) of erythrocytes from 26 anuran species show a linear and direct correlation with the nuclear DNA content; the Cs/Cv ratio tends to decrease as DNA increases. Analogous phenomena are found in urodeles possessing less than 70 pg/N of DNA, whereas in those with a larger genome there is a trend towards stabilization of the Cs/Cv ratio. The same mechanisms appear to control the ratios of genome sizes to cell sizes within the amphibians and possibly in other vertebrates as well. The former, however, seem to avail themselves to a greater extent of the adaptive properties inherent in their genome and cell size variations.Research supported by a grant from the Italian CNR.     

Cross-presentation of IgG-containing immune complexes

IgG is a molecule that functionally combines facets of both innate and adaptive immunity and therefore bridges both arms of the immune system. On the one hand, IgG is created by adaptive immune cells, but can be generated by B cells independently of T cell help. On the other hand, once secreted, IgG can rapidly deliver antigens into intracellular processing pathways, which enable efficient priming of T cell responses towards epitopes from the cognate antigen initially bound by the IgG. While this process has long been known to participate in CD4⁺ T cell activation, IgG-mediated delivery of exogenous antigens into a major histocompatibility complex (MHC) class I processing pathway has received less attention. The coordinated engagement of IgG with IgG receptors expressed on the cell-surface (FcγR) and within the endolysosomal system (FcRn) is a highly potent means to deliver antigen into processing pathways that promote cross-presentation of MHC class I and presentation of MHC class II-restricted epitopes within the same dendritic cell. This review focuses on the mechanisms by which IgG-containing immune complexes mediate such cross-presentation and the implications that this understanding has for manipulation of immune-mediated diseases that depend upon or are due to the activities of CD8⁺ T cells.     

Activity of soluble factors produced by Epstein-Barr virus-transformed human B lymphocytes on different cell lines.

Self-stimulatory growth factors, produced by a human Epstein-Barr virus (EBV)-positive lymphoblastoid B cell line, named BA-D10-4, have been tested for the capacity to induce DNA synthesis in various human and animal cell lines, including lymphoid, either EBV-positive or EBV-negative, and non-lymphoid cell lines. It has been found that BA-D10-4 cells produce growth factors which seem to be essential for their sustained proliferation in vitro, and which increase DNA synthesis in different primate lymphoid cells, independently of the presence of the EBV genome and of the lymphocyte lineage.     

Changes in erythrocyte membrane lipid composition affect the transient decrease in membrane order which accompanies insulin receptor down-regulation.

We have recently demonstrated, using electron paramagnetic resonance (EPR) spectroscopy, that insulin receptor internalization in response to insulin incubation (down-regulation) in human erythrocytes is accompanied by a transient decrease in membrane order, as measured by the 2T' parallel order parameter. Since membrane lipids play such an important role in receptor internalization, we investigated the possible effects that an alteration of the normally-occurring lipid profile might have on down-regulation and the concomitant transient decrease in membrane order. Consequently, human erythrocytes enriched with cholesterol and erythrocytes from cirrhotic patients were examined, because both of these groups of cells have a higher cholesterol/phospholipid molar ratio (CH/PL) than controls. The 5-nitroxystearate spin label, which inserts into the lipid bilayer of cell membranes, was used to monitor changes in 2T' parallel for a 3-h period at 37 degrees C. We report here that both cholesterol-enriched and cirrhotic erythrocytes do not down-regulate, as demonstrated by binding assays, and that they do not show the typical transient decrease in membrane order observed in controls. The results seem to indicate that a more ordered membrane inhibits internalization of the insulin receptor in erythrocytes, and that an increase in membrane disorder is necessary for insulin receptor down-regulation.     

Absence of relationship between erythrocyte and viral antigen expressed on the surface of chick erythrocytes]

Anti-gs antisera were tested on embryo and adult Chick erythrocytes. Specific immunsera directed against Chick embryo or adult erythrocyte antigens have been tested on Hamster cell lines infected with the Rous virus. Results demonstrate that the erythrocyte and viral antigens are different.     

Peripheral erythrocyte levels, hemolysis and three vanadium compounds

Three vanadium compounds of different valence states were administered to adult mice. Two, four, and eight days following treatment of vanadium, cardiac blood was collected. The blood sample was used to ascertain the peripheral erythrocyte count (cell/mm3) and to determine the in vitro hemolytic index of erythrocytes obtained from mice treated in vivo with either the tri-, tetra-, or pentavalent vanadium compound. Data indicate that the tetravalent form was the most effective test substance in 1) promoting rupture of isolated erythrocytes compared to red cells retrieved from control mice and 2) depressing the erythrocyte count obtained from heart blood; maximum effects were manifest four days post-treatment. For all treatments there appeared to be a good correlation between the degree of vanadium-induced hemolysis and the peripheral erythrocyte count reduction following exposure to the vanadium.     

Variation in delayed hypersensitivity to methylated bovine serum albumin as as function of the dose and time of administration of cyclophosphamide]

The injection of Cy before immunization provokes an intensification of delayed-type hypersensitivity (DTH) to methylated bovine serum albumin (M-BSA) and a diminution of about 90% of the cell number in various lymphoid tissues. The relationship between these observations, the time of administration, the dose of injected Cy and the intensity of DTH reactions, allows us to formulate hypotheses concerning the physiological modulation of DTH.