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Biomedical subjects

B Vray

Publications and source records attributed to B Vray.

34 records · Page 2Linked to original sources
PubMed1984

Wheat germ agglutinin potentiates uptake of bacteria by murine peritoneal macrophages.

Exposure of thioglycollate-elicited murine peritoneal macrophages to wheat germ agglutinin (WGA) increased markedly the uptake of six different bacteria, which have surface receptors for the lectin. Uptake of Staphylococcus aureus H was higher by 3-5-fold, of S. aureus 52A2 by 1.8-fold, of S. aureus 52A5 by 1.7-fold, of S. albus by 2.3-fold, of Shigella flexneri by 6-fold and of Micrococcus luteus by 6.5-fold. Klebsiella pneumoniae, devoid of receptors for WGA, was not phagocytosed following pretreatment of macrophages with the lectin. Pretreatment of the bacteria with the lectin also resulted, in most cases, in an increase in phagocytosis. Interaction of WGA with the macrophages and with the bacteria, as well as the potentiation of phagocytosis, was abolished by tri-N-acetylchitotriose, a saccharide that binds specifically to WGA, but not by monosaccharides which do not interact with this lectin. With non-elicited macrophages, enhancement of phagocytosis by WGA was less pronounced, probably because of the higher number of lectin-binding sites (5-fold) on the elicited cells. Peanut agglutinin and soybean agglutinin, that bind to macrophages but not to the bacteria studied, lack the ability to potentiate phagocytosis. Macrophage surface sugars thus appear to play an important role in phagocytosis by serving as receptors for lectins that form bridges between the macrophages and the microorganisms.

Animals↗
PubMed1984

[Macrophage phagocytic function].

Described a century ago by Metschnikoff , phagocytosis plays an essential role in the defence of organisms faced with bacterial infection. Phagocytosis is ensured essentially by neutrophils and macrophages. In cases of inflammatory response, chemotactic factors induce an afflux of neutrophils which predominate at the site of infection for the first few hours. Then macrophages intervene to try and eliminate the infectious agent. If the latter can be rapidly ingested and degraded, the inflammatory response will gradually dwindle . On the other hand, if the infection persists (bacteria resistant to phagocytosis, or to bactericidal agents), the inflammatory response will become chronic. Macrophage anti-bacterial activity is therefore essential and can be broken down into several stages: first chemotaxis, which initiates macrophage migration towards the inflammatory focus. Then adherence to bacteria, via opsonins and membrane receptors. This binding releases an intra-cytoplasmic signal which governs the following stages, i.e. actual ingestion (phagocytosis), then enzymatic destruction within phagolysosomes " bactericidosis ". The phase of recognition and membrane binding to bacteria thus occupies an important place in the physiological role of macrophages. Two receptors are especially involved: the Fc receptor and the C3b receptor. The ingestion phase appears to be initiated by the redistribution of these membrane receptors, which first reform in "micro-clusters" (reversible small aggregates), then in "clusters" (irreversible larger aggregates), which finally become "patches" and "caps". " Bactericidosis " then ensures in most cases the disintegration of the infectious agent, by systems that can be either dependent or independent of oxygen. The main techniques for the study of macrophage phagocytosis are briefly reviewed.

Animals↗
PubMed1983

Genetic deficiency of C4 presenting with recurrent infections and a SLE-like disease. Genetic and immunologic studies.

A young girl presenting with recurrent pulmonary infections and atypical lupus erythematosus was totally deficient in C4. In one sister, also deficient in C4, the same symptoms developed. Results of family studies were consistent with an autosomal recessive mode of transmission and with linkage of the genes determining C4 deficiency to those of the major histocompatibility complex. The patient's serum and red cells were Chido- and Rodgers-negative. Humoral and cellular immunity were normal, except for a low lymphocyte response in mixed lymphocyte culture. The cellular function of the patient's polymorphonuclear leukocytes was normal, for both phagocytosis and bactericidal activity using Candida albicans. However, in the presence of C4-deficient serum, opsonin generation and bactericidal indexes were diminished. These defects were completely reversible upon addition of purified C4.

Child, Preschool↗
PubMed1981

Switched allotype expression in an immunoglobulin-nonsecreting rabbit lymphoid cell line fused with rabbit gangliocytes.

The Simian virus 40-transformed rabbit spleen cell TRSC-1 synthesizes intracellular whole IgG molecules of the alb4 allotype. Two hypoxanthine-guanine phosphoryl transferase-deficient mutants were derived from this line. One of these, TRSC-1-8, was used in somatic cell fusion experiments together with gangliocytes from a rabbit immunized against beta-galactosidase. Out of nineteen hybrid clones surviving in selective medium, only one, L17, was shown to produce free gamma chains which express the a2 allotype of the donor rabbit rather than the al marker of the parents TRSC-1-8 line. The inability to restore IgG secretion in hybrids suggests that dominant regulatory controls are exerted by the TRSC-1 genome on Ig reduction. This supports the notion that the TRSC-1 line originated from a splenocyte that had not reached the final plasmocyte differentiation stage at the time of viral transformation.

Animals↗
PubMed1980

Anti-alprenolol anti-idiotypic antibodies bind to beta-adrenergic receptors and modulate catecholamine-sensitive adenylate cyclase.

Rabbit antibodies induced against alprenolol, a potent beta-adrenergic antagonist, bind to other antagonists, and, with less avidity, to catecholamine agonists. Anti-idiotypic antibodies were raised against the anti-alprenolol immunoglobulins. The anti-idiotypic antibodies specifically bind and agglutinate turkey erythrocytes; this is not observed for human agglutinate turkey erythrocytes; this is not observed for human or sheep erythrocytes, which are devoid of beta-adrenergic receptors. The anti-idiotypic antibodies compete with (--)-[3H]-dihydroalprenolol for binding on the beta-adrenergic receptors on purified turkey erythrocyte membranes. The binding to the membrane-bound receptors is prevented by preincubation of the anti-idiotypic antibodies with their immunogen, the antialprenolol immunoglobulins. The binding to the receptor is not merely passive: the anti-idiotypic antibodies stimulate basal adenylate cyclase activity [ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1] and enhance adenylate cyclase activation by catecholamine. These observations support the notion that antiidiotypic antibodies may constitute an "internal image" of the original antigen and may mimic its biological effects.

Adenylyl Cyclases↗
PubMed1980

SEM morphological studies of phagocytosis by rat macrophages and rabbit polymorphonuclear leukocytes.

Peritoneal rat macrophages and rabbit polymorphonuclear leukocytes were obtained after thioglycollate or glycogen stimulation. Optimal conditions for phagocytosis were determined by a recently developed quantitative fluorimetric assay. We studied by serial SEM micrographs macrophages and polymorphonuclear leukocytes incubated either in medium or in the presence of different types of phagocytic particles. We compared the morphological aspects of adsorption and phagocytic processes for opsonized microorganisms (Micrococcus lysodeikticus and Candida albicans) with these for inert beads of iron and metallic mercury. Without phagocytosis, in the presence of fresh homologous serum, we observed a progressive development of microvilli or lamellipodia in ruffles and by the end, hypertrophied ruffles appeared at one pole of the cell. We noted extremely well developed ruffles during phagocytosis of opsonized microorganisms. These were practically absent on the macrophages incubated with inert particles. The mean number of adsorbed particles is more elevated in the case of iron and metallic mercury beads than for microorganisms. The rate of ingestion of inert particles was considerably higher than for microorganisms even when they were opsonized. In conclusion, at all stages of the phagocytic process, we observe different morphological features of the macrophages depending on the nature of the phagocytosed particles.

Animals↗