[Physiopathology of the mechanism of activation of neutrophils: a future pathway?]

Numerous agonists such as chemotactic factors, phorbol esters, calcium ionophores, arachidonic acid or particles induce a cascade of events associated to oxygen reduction, the oxidative burst, in phagocytes and specially in neutrophils. Diverse transductional pathways involved in the oxidative burst were described. Moreover, various pathologies of the transductional pathways in different cell systems were recently observed. We think that the study of neutrophils constitutes first an excellent model of Cell Biology and second a putative model of the physiopathology of the transductional pathways.

Quantification of the nonspecific intercellular transfer of fluorescent molecules between labeled and unlabeled rat thymocytes

Fluorescein isothiocyanate has been used to label normal or tumor cells in order to study their migration in vivo. This requires that any transfer of fluorescence to neighbouring cells be carefully ruled out. The aim of the present report is to demonstrate the possibility of a transfer of fluorescein or fluorescein-bound molecules between untreated and labeled cells. When normal rat thymocytes were co-incubated with labeled cells (about 5 X 10(6) fluorescein molecules/cell) under continuous agitation or exposed to supernatants of these labeled cells, they bound an average of 10(4) fluorescein molecules. When the incubation was done on cell pellets after centrifugation, this transfer was increased tenfold. Hence, intercellular molecular exchange may occur in the absence of any specific interaction.

Use of cell contour analysis to evaluate the affinity between macrophages and glutaraldehyde-treated erythrocytes

Recently, several authors evaluated the affinity between lipid bilayers or erythrocyte membranes by analyzing the deformation of cells or vesicles they brought into close contact using micromanipulators. In the present report, we extend this approach in a study of the adhesive properties of rough nucleated cells. Rat peritoneal macrophages were made to bind human red cells modified with glutaraldehyde or glutaraldehyde and polylysine. Conjugates were examined with electron microscopy, and photomicrographs were digitized for quantification of cell surface roughness in and out of adhesion areas. Also, macrophages were subjected to micropipette aspiration to find a relationship between apparent surface tension and area increase. Assuming that this increase was a direct consequence of a smoothing of the cell surface on the submicrometer scale, the actual affinity between macrophages and erythrocytes was estimated. The obtained values ranged between 8.4 X 10(-5) and 18.2 X 10(-5) J/m2. It is concluded that cell surface roughness may be an important parameter of cell adhesion and perhaps deformation. This is made amenable to experimental study by the present approach.

Study of CTL and LAK contacts to target cells after treatment with mitomycin C and adriamycin

We tried to understand the role of Mitomycin C and Adriamycin in the increased killing of target cells by Cytotoxic T lymphocytes (CTL) and lymphokine activated killers (LAK). For this purpose, we used an objective method allowing quantitative evaluation of the roughness of cell contours on electron micrographs. We compared the folding of the membranes of LAK and CTL as well as conjugated targets exposed to different treatments. We demonstrated first that CTL and LAK displayed similar morphological patterns: the killer cells were more villous than targets in the free areas, and second that the former cells exhibited significant smoothing on the areas of contact with these targets. These results suggest that the binding process (as distinct from the recognition step) is dependent on killer properties which are the same in CTL, LAK and probably NK cells.

Abnormalities of some phagocyte membrane receptors during nosocomial infections

The frequent and severe nosocomial infections in ICU patients suggest that these patients are immunodeficient. We studied the phagocytic activity of granulocytes and monocytes isolated from the blood of 32 ICU patients with nosocomial pneumonia (19 male, 13 female; age 41 +/- 4 yr). Cells were tested in standard medium and in the presence of patients' serum. Blood granulocytes and monocytes were purified and separately exposed to opsonized zymosan (to test C3 receptor function), immunoglobulin-coated erythrocytes (to test Fc receptor function), and glutaraldehyde-treated erythrocytes (to test nonspecific binding structures). Phagocytosis and superoxide anion production were measured. Granulocytes of patients exhibited a substantial decrease of zymosan ingestion (p less than .05), whereas phagocytosis of other particles was normal. Monocytes from the patients displayed an unselective overall decrease of phagocytic ability for the three particle types (p less than .05). Patients' sera were at least as efficient as a pool of normal sera in opsonizing zymosan. Further, no phagocytic inhibitor was found in the tested patients. In conclusion, we point out a deficiency of membrane receptors of neutrophils and monocytes in ICU patients with nosocomial infection.

Role of the quaternary ammonium ion determinants in allergy to muscle relaxants

Anaphylaxis to muscle relaxants appears to be a very useful model to study the IgE-dependent mechanisms of mediator release in humans. The serum IgE binding sites of the drugs appeared to be the ammonium ion determinants. In patients allergic to suxamethonium, one of the most frequently used muscle relaxants for general anesthesia, significant histamine release could be obtained in each case with simple diammonium salts. The length of the chain linking the ammonium groups appears to play an important role. In fact, when the length was less than or equal to 4 A, no significant histamine release could be obtained, whereas the optimal length for histamine release appeared to be greater than or equal to 6 A. Furthermore, muscle relaxants with a rigid backbone between the ammonium determinants (such as pancuronium) are less active than flexible molecules (such as suxamethonium) in initiating mediator release. This study suggests that small divalent molecules can induce anaphylactic shock in sensitized patients and that the length and the flexibility of the chain bearing the haptenic determinants appear to be important factors in the elicitation of mediator release.

Analysis of cell structural and functional diversity by combination of micromanipulation and microfluorimetry

Fluorescent molecules are widely used to study quantitative cell properties, such as density of different antigenic markers or membrane responses to various stimuli. In most cases, studies are done on bulk cell populations with a spectrofluorimeter or at the single cell level with a cytofluorograph. However, only microspectrofluorimetric techniques allow continuous recording of dynamic events undergone by individual cells. The aim of the present report was twofold: first, to describe a methodology easily accessible to cell biologists that allows simultaneous manipulation of single cells and measurements of their fluorescence properties; and second, through this methodology to study quantitative aspects of cell structure and function such as binding of a fluorescein-labeled lectin, transfer of fluorescent molecules between labeled and unlabeled cells brought in close contact, or fluorescence response of individual cells stimulated after being loaded with a potential-sensitive dye. We conclude that the understanding of many aspects of cell structure and behavior requires that individual cells be studied under dynamic conditions and for prolonged periods of time.

Self-limitation of the oxidative burst of rat polymorphonuclear leukocytes

The oxidative response of rat polymorphonuclear leukocytes stimulated by phorbol myristate acetate and N-formyl-methionyl-leucyl-phenylalanine was studied. Ferricytochrome reduction and peroxidase-catalyzed decrease of scopoletin fluorescence were used to monitor O-2 and H2O2 release in the extracellular medium. Oxygen consumption was also measured in some experiments. Decrease of chlortetracyclin fluorescence after stimulation of dye-loaded cells was used to study an early step of cell stimulation. Finally, a possible relationship between cell responses and the medium redox potential was explored. Three major conclusions were obtained: Ferricytochrome reduction is dependent on the total cytochrome concentration, and a simple mathematical model allows a tentative estimate of total superoxide anion production by stimulated cells. Increasing cell concentration results in a decrease of individual cell response, and this may be accounted for by a direct inhibition of cell-released hydrogen peroxide on the reactivity of leukocytes. Further, H2O2 may be shown to inhibit an early step of cell response. The solution redox potential does not influence cell reactivity, since it may be dramatically decreased without inhibiting cell response.

Determination of binding strength and kinetics of binding initiation. A model study made on the adhesive properties of P388D1 macrophage-like cells

The adhesive properties of the mouse P388D1 macrophage-like line were explored. Cells were deposited in glass capillary tubes, and the kinetics of adhesion and spreading were studied. Binding involved the cell metabolism since it was decreased by cold, azide, or a divalent cation chelator. Glass-adherent cells were subjected to calibrated laminar shear flows with a highly viscous dextran solution. A tangential force of about 5 X 10(-3) dyn/cell was required to achieve substantial detachment. The duration of application of the shearing force strongly influenced cell-substrate separation when this was varied from 1-10 s. Further, this treatment resulted in marked cell deformation, with the appearance of an elongated shape. Hence, cell-substrate separation is a progressive process, and binding strength is expected to be influenced by cell deformability. The minimum time required for adhesion was also investigated by making cells adhere under flow conditions. The maximum flow rate compatible with adhesion was about 1000-fold lower than that required to detach glass-bound cells. A simple model was devised to provide a quantitative interpretation for the experimental results of kinetic studies. It is concluded that cell-to-glass adhesion required a cell-substrate contact longer than a few seconds. This first step of adhesion was rapidly followed by a large (about 1000-fold) increase of adhesion strength. It is therefore emphasized that adhesion is heavily dependent on the duration of cell-to-cell encounter, as well as the force used to remove so-called unbound cells.

Quantification of cell surface roughness; a method for studying cell mechanical and adhesive properties

The presence on the surface of nucleated cells of a variety of asperities of different size and shape plays a prominent role in cell-cell and cell-substrate interaction. Also, the organization of these asperities is directly related to cellular cytoskeletal elements. In the present report, we describe a simple and objective method of studying electron micrographs to quantify the roughness of cell contours. Constant-length segments of cell boundaries are compared to reference circular segments with common extremities and enclosing the same area. This procedure was performed with a digitizer connected to a microcomputer, and it was used to analyse model contours or electron micrographs of (i) target tumour cells bound by cytotoxic T lymphocytes and (ii) thymocytes sticking to concanavalin A-coated surfaces. It is shown that this method allows precise quantification of cell deformation in adhesive zones, which may allow absolute evaluation of adhesive stimuli.

[Role of phagocytic cells in rheumatoid polyarthritis]

Three groups of subjects were selected for this study. Patients suffering from rheumatoid arthritis (RA) diagnosed according to the criteria of the ARA (mean: 6 criteria) and treated with gold salts. Control subjects treated with one type of non-steroidal anti-inflammatory agent (diclofenac). Healthy subjects receiving no treatment. The granulocytes and monocytes in the peripheral blood were tested separately for the ingestion of 3 types of particles and for the stimulation of the production of the superoxide anion. In the patients with rheumatoid arthritis, all of the phagocytic cells had a normal phagocytic response and a normal superoxide anion production. The serum of the patients did not inhibit the activity of these cells. Diclofenac did not act on phagocytosis or on the oxidative activity of the control cells. It is therefore logical to consider that the phagocytic cells are involved in RA via other mechanisms of action.

Monocytes and granulocytes in rheumatoid arthritis (RA): phagocytic activity and superoxide anion production

It is suggested by many tests that phagocytic cells were implied in inflammation which occurred during rheumatoid arthritis (RA). Further, three subject populations were selected for this study: Rheumatoid arthritis patients diagnosed according to American Rheumatism Association criteria (ARA mean = 6) and treated with gold compounds. Control subjects treated with the same non-steroidal anti-inflammatory drug (NSAID), diclofenac (75 mg per day). Normal subjects without disease or treatment. Blood granulocytes and monocytes were separately tested for ingestion of three different particle species (opsonized zymosan, immunoglobulin G sheep red cells, glutaraldehyde-treated sheep red cells) and stimulation of superoxide anion production by these particles. All phagocytic cells in RA patients have normal phagocytic response and superoxide anion production. Autologous serum does not inhibit the activity of these cells. In addition the NSAID (diclofenac) does not act upon phagocytosis and oxidative burst of control cells.

Study of cell deformability by a simple method

Cell deformability plays an important role in many immunological processes, such as phagocyte chemotaxis and endocytosis. The most widely used method of assay consists in aspirating cells into glass micropipettes and measuring the length of the protrusion induced by a given pressure, or the minimum pressure required to drive cells into the micropipette. This procedure requires specialized equipment and delicate manipulation. The present report describes a simpler procedure: cells are centrifuged in petri dishes floating on a water cushion, then fixed and coated with 0.8 micron diameter latex beads, which allows rapid and accurate determination of their height. This method is compared with the micropipette technique by studying lymphocyte and macrophage-like cell lines in physiological medium and in the presence of a divalent cation chelator or a microfilament inhibitor. In addition to simplicity, the main advantages of this technique are that (i) many cells may be examined within a reasonable period of time, which allows testing of heterogeneous cell populations, and (ii) unexpectedly, centrifugation was quite harmless under our experimental conditions, since it did not impair cell proliferative ability nor phagocytic ability. It is concluded that the method may be used in clinical laboratories to explore phagocyte dysfunctions, as well as in experimental studies.

Unexpected cell surface labeling in conjugates between cytotoxic T lymphocytes and target cells

Specific binding of target cells by cytotoxic T lymphocytes (CTL) is an example of tight interaction between two different cell types. The molecular events that occur at the cell membranes during these interactions are largely unknown. In the present report, we describe an electron microscopic immunostaining study made on CTL-target cell conjugates. Various membrane structures were labeled with monoclonal antibodies specific for structures possibly relevant to cytolysis (Lyt-2, LFA-1, and target cell class I major histocompatibility antigens) or probably unrelated to the cytolytic process (effector cell class I major histocompatibility antigens). Antibodies against Thy-1 were also used. Staining was achieved with immunoperoxidase or immunoferritin. With both techniques nonconjugated cells were either stained or not, depending on whether they bore the antigen corresponding to the antibody used. However, when conjugated to an antigen-bearing cell, a "non-antigen bearing" cell was labeled near the cell interaction area. No increased Fc receptor activity could be detected on bound cells near the interaction area. These data are consistent with the occurrence of limited exchange of membrane macromolecules between bound CTL and target cell.

Leukocyte histamine release to suxamethonium in patients with adverse reactions to muscle relaxants

In an earlier study we confirmed the usefulness of intradermal skin tests and histamine release in diagnosis of patients reactive to muscle relaxants, and we suggested an IgE-mediated reaction rather than an idiosyncratic mechanism. In a later study, we studied the relationship between (Formula: see text) that is one of the muscle relaxants producing the most frequent adverse reactions under anesthesia. Histamine release was measured in five patients with increasing concentrations of suxamethonium in the presence or absence of human serum albumin in Tris buffer. Suxamethonium by itself without any carrier in the buffer could, in vitro, act as a true allergen on target leukocytes in the sensitized patients' group. Acetylcholine (20 and 200 micrograms/ml) did not induce significant histamine release in five patients with positive histamine release in the presence of suxamethonium. Preincubation of leukocytes from 11 patients for 30 min with 20 and 200 micrograms of acetylcholine in Tris albumin CA++ Mg++ buffer decreased the histamine release induced by suxamethonium (10 micrograms/ml); mean maximal histamine release of 46% +/- 4.2 was reduced to 31.4 +/- 5.8 and 7% +/- 4 (p less than 0.001), respectively. However, in eight control subjects similar concentrations of acetylcholine did not change the maximal histamine release induced by anti-IgE (0.2 micrograms/ml). In the same way acetylcholine did not modify histamine release induced by Dermatophagoides pteronyssinus extract (1/10,000 w/v) in six patients allergic to this allergen. This study suggests that suxamethonium acts as a true allergen and that acetylcholine or one of its metabolites may act as a hapten inhibitor in the model of histamine release induced by suxamethonium.(ABSTRACT TRUNCATED AT 250 WORDS)

T-cell-fibroblast hybridoma deformability and concanavalin A-induced agglutination

Cell adhesion influences many important immunological functions such as phagocytosis or T-cell-mediated cytotoxicity. Previous work suggested that the ease of inducing intercellular bonds (i.e. binding efficiency) and the difficulty to separate bound cells with mechanical forces (i.e. binding strength) might be parameters of different significances. The present report describes a study made on two T-lymphocyte/polyoma virus transformed fibroblast hybrid subclones (3D1c and 3D1n) with markedly different adhesive properties: indeed, 3D1c cells were at the same time more readily agglutinated with concanavalin A and more easily disagglutinated than 3D1n. In order to understand these differences, a systematic comparison of various properties of 3D1c and 3D1n cells was undertaken. The following parameters were studied: surface density of concanavalin A binding sites, surface electrostatic charge, hydrophobicity, fluorescence polarization measured on individual cells, and ability to spread on a flat substrate in response to volume or surface forces. It is concluded that cell deformability and/or spreading ability might be an important determinant of binding strength, but the factors governing binding efficiency remained incompletely understood. It is suggested that the methods described in the present report might help understanding differences between various tumor cell lines with different malignant potential.

[Anomalies of the membrane receptors of blood phagocytic cells in nosocomial pulmonary infections]

Patients in intensive care units have frequent and severe opportunistic bacterial pneumoniae, even if they were previously free from respiratory disease. A search was made in these patients for possible immune deficiencies. Granulocyte and monocyte phagocytic activities were studied separately in 17 patients with bacterial bronchopneumonia (male: 13, female: 4; age: 41 +/- 5 yr). The ability of three types of particles (opsonized zymosan, immunoglobulin coated and glutaraldehyde-treated sheep red cells) to trigger ingestion was measured. Cells were tested either in normal AB serum or in the presence of patient's serum. A substantial 40% decrease of the fraction of granulocytes ingesting zymosan was found in our experimental conditions (p less than 0.001). Activity with the other particles was not significantly altered. Patients' sera were at least as efficient as a pool of normal sera in opsonizing zymosan. Furthermore, no phagocytic inhibitor was found in the patients tested. Underlying mechanisms for these abnormalities remain unknown, but a better understanding of the aetiology of the altered bactericidal function of phagocytic cells is required before suggesting immunomodulating treatments.

Effect of age on different receptors and functions of phagocytic cells

Different tests were performed on 15 young (age between 17 and 39) and 13 older (62-83) subjects. Blood polymorphs and monocytes were separately tested for ingestion of 3 different particle species and stimulation of superoxide anion production. The erythrocyte sedimentation rate and the serum concentrations of 10 proteins possibly related to inflammatory processes were also determined. It is concluded that: Individual variations of phagocyte ability to be stimulated by different cell types are independent processes. Aged people displayed selective decrease of Fc receptor-mediated phagocytosis by granulocytes and possibly selective impairment of nonspecific phagocytosis by monocytes. Further, the IgM level was decreased whereas the IgA, C-reactive protein and erythrocyte sedimentation rate were higher in old people than in young subjects. Correlations were found between the serum concentrations of some protein species and phagocytic function, but further experiments were coincidental (if both parameters were age-related) or revealed some causal link. It is suggested that our procedure provides a simple and reproducible way of testing many independent functions of phagocytic cells.

Cell adhesion. Competition between nonspecific repulsion and specific bonding

We develop a thermodynamic calculus for the modeling of cell adhesion. By means of this approach, we are able to compute the end results of competition between the formation of specific macromolecular bridges and nonspecific repulsion arising from electrostatic forces and osmotic (steric stabilization) forces. Using this calculus also allows us to derive in a straightforward manner the effects of cell deformability, the Young's modulus for stretching of bridges, diffusional mobility of receptors, heterogeneity of receptors, variation in receptor number, and the strength of receptor-receptor binding. The major insight that results from our analysis concerns the existence and characteristics of two phase transitions corresponding, respectively, to the onset of stable cell adhesion and to the onset of maximum cell-cell or cell-substrate contact. We are also able to make detailed predictions of the equilibrium contact area, equilibrium number of bridges, and the cell-cell or cell-substrate separation distance. We illustrate how our approach can be used to improve the analysis of experimental data, by means of two concrete examples.

Nonspecific cell surface properties: contact angle of water on dried cell monolayers

Measuring contact angle of water on dried cell or bacterium monolayers allowed van Oss (1) and others (2) to find a correlation between particle hydrophobicity and ingestion by phagocytic cells. The present study was undertaken to understand what was actually assayed with this method. Monolayers were prepared with different cell types at different densities, and they were dried under atmospheres with varying humidity before being studied with scanning electron microscopy and contact angle techniques. It is concluded that a) contact angles are independent of the cell density and substrate structure when more than 30% of the substrate area is covered with cells. b) Initial cell shape should not influence contact angle. c) Contact angles are markedly dependent on the nature of tested cells. d) Contact angles are substantially influenced by the cell drying procedure. e) A very small fraction of the energies we measured would be sufficient to account for cell-cell interactions. Hence these might play a role in some situations of biological interest.

Dissociation between phagocytosis and phagosome-lysosome fusion

The acridine orange technique was used to explore phagosome-lysosome fusion (P-L fusion) in thioglycollate-elicited rat peritoneal macrophages. Sheep red blood cells were coated with IgG or IgM plus complement, or treated with neuraminidase, tannic acid or glutaraldehyde; then both their capacity to be ingested by macrophages and their ability to induce P-L fusion after ingestion were assayed. Their capacity to be engulfed by macrophages was similar, but glutaraldehyde-treated erythrocytes were far more efficient than the other particles in triggering P-L fusion. Hence, both processes must be driven by different mechanisms. No correlation was found between the surface charge of test particles (as assayed by cell electrophoresis) and their ability to trigger phagocytosis or P-L fusion. However, glutaraldehyde-treated erythrocytes were found to be more hydrophobic than the other particles, as previously reported. Hence, particle hydrophobicity might favor P-L fusion. The implication of these findings are discussed.

Dimethylsulphoxide induction of the murine macrophage-like line P388D1: change of phagocytic ability and cell surface properties

The murine macrophage-like cell line P388D1 ingests immunoglobulin-coated sheep red cells (IgG-SRC) poorly, but after 3 days incubation in the presence of 1.5% dimethyl sulphoxide (DMSO), it becomes highly phagocytic. We used this model to correlate triggering of phagocytosis with some surface properties of P388D1 cells, possibly involved in recognition or engulfment of particles. The accessibility of Fc receptors on the cell membranes did not seem to be affected by DMSO treatment since the binding of IgG-SRC to cells was the same before and after treatment with DMSO. A technique allowing quantitative determination of the stability of cell-particle binding showed that binding strength was not the only essential factor in triggering ingestion. Hydrophobicity and surface charge were postulated to play a role in phagocytic recognition. No change in hydrophobicity, as assayed by contact-angle measurement, and in net surface charge evaluated by cell electrophoresis, was observed for normal and DMSO-treated P388D1 cells. On the other hand, the fluorescence polarization of a membrane lipophilic probe (1,6-diphenyl-1,3,5-hexatriene) was significantly (P less than 0.01) decreased when P388D1 cells were treated with DMSO. Since the effect of DMSO on P388D1 function was delayed, our results were consistent with the view that enhancement of phagocytosis might be a consequence of some modification of membrane dynamics, due to changes in lipid composition.

T cell-mediated cytolysis: on the strength of effector-target cell interaction

Allosensitized lymphoid cell populations contain T lymphocytes that can bind to target cells and lyse them. We asked whether there was a relationship between lymphocyte target cell-binding strength and occurrence of cytolysis. Using graded shear forces to dissociate effector-target cell conjugates, we found that (a) within an allosensitized lymphoid cell population derived from an heterogeneous mixed leukocyte culture, there were lymphocyte-target cell conjugates with binding strengths differing by a factor of at least 10(2), (b) even the minimal force required to release a significant amount of bound target cells could disrupt the plasma membranes of some tumor cells and (c) these tumor cells disrupted by shear forces were probably part of cytolysis-conducive rather than of non-cytolysis-conductive conjugates. We combined this approach with the use of cytolysis-inhibiting monoclonal antibodies (mAb), and found that antibody-induced decrease of cytolysis was correlated with a decrease in the percentage of strong or total conjugates, depending on the mAb used. When lectins were added to overcome the inhibitory effect of the mAb, reappearance of cytolytic activity correlated with reappearance of conjugates. This was especially striking using wheat germ agglutinin (WGA): the addition of WGA to irrelevant effector-target cell combinations did not lead to cytolysis; however, the addition of WGA to relevant effector-target cell combinations inhibited by mAb led to reappearance of cytolysis and of strong conjugates. Taken together, these and other results suggested that under our experimental conditions a threshold level of binding strength between effector and target cells might be important, although not sufficient, for T cell-mediated cytotoxicity. These results were not inconsistent with the involvement of mechanical factors in this process. Also, they were in line with the concept of nonantigen-specific lymphoid cell surface interacting molecules, detected by the mAb used and important for the establishment of strong, functional lymphocyte target cell interactions. Finally, they underlined the necessity of a quantitative estimate of cell-cell binding strength when investigating the effect of a given agent (e.g. a mAb) on lymphocyte target cell recognition.