Selective inhibition of human neutrophilic chemotaxis by echo virus, type 9. Virus-induced changes in membrane fluidity

Viral-bacterial synergistic interaction in respiratory disease

In the present review we have identified how viruses can alter the host's susceptibility to bacterial infections by altering both environmental conditions in the lung which favor bacterial replication as well as by suppressing the host's defense mechanisms which prevent clearance of the bacteria. In many instances, these interactions are extremely complex but similar for many viruses. If the virus can overcome the initial host defense mechanisms, which include local antibody and mucus, the virus initiates tissue damage as a result of direct replication within the epithelial cells lining the mucosal surfaces of the respiratory tract. As a result of virus infection, the host cells respond by producing a variety of mediators including various types of interferons, which can alter both virus replication and host response. Replication also produces by-products of virus infection capable of initiating an inflammatory process, which in turn, through release of other mediators, can further modify lung defense mechanisms and encourage bacterial adherence and growth. The bacterium, in turn, releases chemotactic factors which encourage infiltration of specific effector cells into the lung. These effector cells can cause tissue damage and immunopathology, which encourage rapid bacterial growth and may result in death of the animal. In order to be able to control this complicated scenario, it is important either to prevent the initial infection with viruses or to reduce the degree of immunosuppression, so that bacterial clearance can occur rapidly before microcolony formation and extensive lung damage occur. Once a large amount of bacterial replication and lung damage is present, the use of antibiotics is generally of limited value. A schematic illustration of the complexity of the various interactions and counteractions occurring during virus--bacterial synergistic interactions is presented in Fig. 1.

Measurement of membrane fluidity of polymorphonuclear leukocytes by flow cytometry

A method was established for measuring membrane fluidity of polymorphonuclear leukocytes (PMN) by the excimer-forming lipid technique with pyrenedecanoic acid in flow cytometry. When cells were labeled, the use of 2-25 microM of pyrenedecanoic acid provided similar results. Neither the removal of the unincorporated pyrenedecanoic acid nor adjustment of PMN counts exhibited any effect. By the gate analysis method, membrane fluidity of PMN could be measured with 100 microliters of heparinized whole blood in a short time and results with PMN in whole blood was similar to those with purified PMN. Therefore, purification and count adjustment of PMN could be omitted. By this method, membrane fluidity of PMN, which were treated with membrane fluidizer, was measured successfully. This method could be applied to the study of PMN function in various diseases.

Alterations in the biophysical properties of the human endothelial cell plasma membrane induced by a chemotactic tripeptide: correlation with enhanced adherence of granulocytes

Human umbilical vein endothelial cells in monolayer culture were used to study the effects of the chemotactic tripeptide, N-formylmethionylleucylphenylalanine (FMLP), on structure and function of the endothelium. Endothelial cell morphology was unaffected by concentrations of 10(-8)-10(-4)M. No effect on endothelial cell proliferative capacity, as measured by the DNA content of cultures, was seen at the FMLP concentrations studied (10(-8)-10(-6)M). Using fluorescent molecular probes to investigate FMLP-induced alterations in membrane structure, it was shown using the monomer-excimer method with pyrene decanoic acid that FMLP caused a marked restructuring of the plasma membrane. This took the form of a restriction of the surface available to the lipophile reporter molecules, probably caused by a molecular reorganization of the membrane protein component. Experiments with diphenylhexatriene indicated that FMLP did not make the plasma membrane of the endothelial cell more fluid. Concomitant with these changes in the physical properties of the membrane, an FMLP-induced increase in granulocyte adherence to the endothelial cells was observed. A theoretical model is presented correlating granulocyte adherence with the lateral mobility of lipids in the endothelial cell membrane. The significance of the FMLP-induced increase in granulocyte adherence to endothelial cells for the pathogenesis of sepsis is discussed.

Effect of bovine recombinant alpha-1 interferon on inflammatory responses of bovine phagocytes

Bovine phagocytic cells (polymorphonuclear granulocytes, blood monocytes and alveolar macrophages) were treated in vitro with homogeneous, recombinant DNA produced bovine alpha-1 interferon (IFN-alpha 1). The effects seen comprised of enhanced bacterial uptake by all three cell types and increased Fc receptor activity in alveolar macrophages, inhibition of both directed and random migration of monocytes and polymorphs, increased enzyme release or inactivation, increased hydrogen peroxide generation, and decreased superoxide anion release by alveolar macrophages and polymorphonuclear leukocytes. These effects were dose- and time-dependent, the kinetics varying for the different cell types.