Human monocyte adherence measured by the nylon fibre microcolumn technique

Attachment, morphology and adherence of human endothelial cells to vascular prosthesis materials under the action of shear stress

In an effort to improve the long-term patency of vascular prostheses several groups now advocate seeding autologous endothelial cells (ECs) onto the lumen of the vessel prior to implantation, a procedure that involves pre-treating the prosthesis material with fibrin, collagen and/or other matrix molecules to promote cell attachment and retention. In this study, we examined the degree to which human umbilical venous endothelial cells (HUVECs) adhered to three materials commonly used polymeric vascular prosthesis that had been coated with the same commercial extra cellular matrix proteins, and after exposure to fluid shear stresses representative of femoro-distal bypass in a cone-and-plate shearing device. We quantified cell number, area of coverage and degree of cell spreading using image analysis techniques. The response of cells that adhered to the surface of each material, and following exposure to fluid shear stress, depended on surface treatment, topology and cell type. Whereas collagen coating improved primary cellular adhesion and coverage significantly, the degree of spreading depended on the underlying surface structure and on the application of the shear stress. In some cases, fewer than 30% of cells remained on the surface after only 1-h exposure to physiological levels of shear stress. The proportion of the surface that was covered by cells also decreased, despite an increase in the degree to which individual cells spread on exposure to shear stress. Moreover, the behaviour of HUVECs was distinct from that of fibroblasts, in that the human ECs were able to adapt to their environment by spreading to a much greater extent in response to shear. The quality of HUVEC attachment, as measured by extent of cell coverage and resistance to fluid shear stress, was greatest on expanded polytetrafluoroethylene samples that had been impregnated with Type I/III collagen.

Tumour promoters/protein-kinase C activators augment the survival and function of human monocyte-derived macrophages in long-term cultures

In this study the effect of various Protein kinase C (PKC) activators/tumour promoters on the maturation and activity of human peripheral blood monocytes was examined. Monocytes were cultured in the absence or presence of various PKC activators for up to 2 weeks, and examined for the number of adherent cells, expression of myeloperoxidase enzymes, CD14 antigens, mannose/N-acetylglucosamine (Man/GlcNAc) receptors, and the production of TNF-alpha. The presence of PKC activators in cultures of monocyte-derived macrophages (HuMoDM) prevented the loss in the number of initially plated monocytes, otherwise observed in long-term tissue cultures with time of incubation. This effect of PKC activators on monocyte survival was diminished in the presence of PKC inhibitors. HuMoDM obtained in the presence of PKC activators maintained a normal differentiation pattern, as was evident by the loss of granular myeloperoxidase enzymes and CD14 antigens, and the acquisition of membrane Man/GlcNAc receptors. HuMoDM which differentiated in the presence of PKC activators also released TNF-alpha in comparable amounts to freshly harvested human monocytes. PKC activators/tumour promoters augmented the viability of long-term cultures of human monocyte-derived macrophages. Such macrophages may facilitate cell and molecular biology studies of differentiated human macrophages.

A micromechanical technique for monitoring cell-substrate adhesiveness: measurements of the strength of red blood cell adhesion to glass and polymer test surfaces

We report a novel method for rapid comparison of the relative strength of adhesion of cells to different solid surfaces. A vertically oscillating micropipette is brought above an individual cell in such a manner that it makes contact with the cell at the lower limit of its travel. The pressure within the micropipette is gradually reduced until the cell attaches to the micropipette by suction and is lifted from the solid surface. The reduction in pressure required to detach a cell depends on the specific cell/substrate combination and serves as a relative measure of the strength of cell adhesion. A particular advantage of this approach over conventional methods is the ability to select particular cells from a population. As a test of the reproducibility of the method and its ability to distinguish the strength of adhesion of cells to different solid surfaces, we have used it to measure the adhesiveness of human red blood cells to hydrophilic glass, tissue culture grade polystyrene, polyethylene terephthalate, and polymethyl methacrylate. We find that results for the same surface are highly reproducible and that the method is capable of distinguishing small differences in the adhesiveness of red blood cells to the above surfaces.

Monocyte-lymphocyte discrimination in a new microtitre-based adhesion assay

A new, rapid and reproducible method is described for the quantification of in vitro monocyte adherence in microtitre 96-well ELISA plates. The assay is based on the measurement of the myeloperoxidase activity in monocytes that have adhered to either plastic or bovine/porcine aortic endothelial cells. The assay shows a linear response to monocyte concentrations over the range 5 x 10(4)-5 x 10(5) cells/well. The method provides good discrimination between monocyte and and lymphocytes and thus allows a study of mononuclear cell populations to be made. The assay works equally well with polymorphonuclear cells. The coefficients of variation are: intra-assay, 7%; interassay, 13%.

Uptake of 3H-deoxyglucose as a microassay of human neutrophil and monocyte activation

The accumulation of 2-deoxy-D-[1-3H]glucose, a non-metabolised analogue of glucose provides a quantitative measurement of the state of activation of phagocytic cells. A microassay for 3H-deoxyglucose uptake by human neutrophils and monocytes is described. Optimal conditions for the assay include the use of 5 X 10(5) cells and 0.78 microCi/ml of deoxyglucose in a final volume of 0.2 ml per microtitre well, and an incubation time of 30 min at 37 degrees C. This simple, rapid and reproducible technique may find application in experimental immunology.

Doxycycline effects on the adherence of polymorphonuclear leukocytes to an albumin-coated glass surface

The effect of doxycycline on polymorphonuclear leukocyte (PMN) adherence to albumin-coated glass surfaces was studied in the absence and presence of the chemotactic peptide FMLP. Three concentrations of doxycycline were studied, one subtherapeutic (0.1 micrograms/ml), one therapeutic (1.0 micrograms/ml) and one supertherapeutic (10 micrograms/ml). PMN adherence was maximal after incubation for 5 min. FMLP did not affect PMN adherence in the present assay system and at the concentration studied (10(-7)M). PMN adherence remained stable and unaffected in the tested doxycycline concentrations. Thus, the present study could not confirm the reported and challenged doxycycline inhibition of PMN adherence.

Sensitive and quantitative determination of monocyte adherence

A new sensitive and highly reproducible one-step ELISA is described to quantitatively determine the adherent capacity of monocytes and related cell lines. Cells were labelled with a monoclonal antibody/peroxidase conjugate which did not affect the adhesive properties of these cells. The labelled cells were allowed to adhere for 1 h and subsequently stained by the addition of substrate. The results demonstrate that there is a good correlation between the number of peroxidase-labelled adherent cells and the absorbance measured at 450 nm. Furthermore the assay permits the use of very low cell numbers since adherent cells could be measured efficiently at a level of only 100-500 cells/well. The method may be very useful in the selection of hybridomas that secrete antibodies which inhibit adherence of cells. In addition it can be applied to study the adhesive properties of any cell type, provided that appropriate monoclonal antibodies are available.

Effect of emetine and chloroquine on phagocytic processes of rat macrophages

Emetine and chloroquine caused a dose-dependent and time-dependent inhibition of bacterial phagocytosis in rat peritoneal macrophages. The effect of emetine was found to be stronger: 50% inhibition was achieved at 5 X 10(-6) M concentration. The inhibition of phagocytosis was irreversible. Neither the binding of bacteria to the surface of phagocytes nor membrane marker 5' nucleotidase was touched by this treatment. The adherence of macrophages to plastic dishes was also impaired by the drugs but only in a smaller extent. Both emetine and chloroquine blocked the amino acid incorporation into macrophage proteins. The effect of emetine was more marked; 10(-6) M decreased the incorporation to 25% of control, while 10(-4) M chloroquine produced a similar inhibition. The block of protein synthesis was also irreversible.

Inhibitory effects of tetrandrine on human neutrophil and monocyte adherence

Tetrandrine is a plant alkaloid useful in the treatment of silicosis. Its mode of action is unknown, but results of the present study show dose-dependent inhibition of human neutrophil and monocyte adherence at concentrations (0.1-10 micrograms/ml) easily achieved in plasma during drug therapy. Monocytes were shown to be more sensitive to tetrandrine than neutrophils. Dye-exclusion experiments indicate that tetrandrine is non-toxic to these cells at 10 micrograms/ml concentrations. Suppression of adherence was reversible by washing, suggesting that the drug does not bind tightly to membrane components. Enhancement of adherence by the tumour promoter, phorbol myristate acetate, was abolished by tetrandrine. The uptake of deoxyglucose by neutrophils and monocytes was suppressed by tetrandrine. These results indicate that tetrandrine may act by interfering with the recruitment of these cells into silicotic lesions.