Interferon induction: tool for establishing interactions among homopolyribonucleotides.

Hitherto unrecognized interactions between homopolyribonucleotides and complexes thereof are suggested by interferon induction data obtained in a highly sensitive assay system of primary rabbit kidney cell cultures superinduced by metabolic inhibitors.

Protective effects of tumor necrosis factor in experimental Legionella pneumophila infections of mice via activation of PMN function.

Tumor necrosis factor (TNF) was found in the lung lavage fluids of Legionella pneumophila-infected mice within 24 hr of intratracheal (i.t.) inoculation. Since this cytokine has been reported to activate polymorphonuclear leukocyte (PMN) function, the effect of TNF on the in vitro bactericidal capacity of PMN-enriched cultures was determined. Murine thioglycollate-elicited PMN which were treated with recombinant human TNF demonstrated augmented killing of L. pneumophila bacteria in vitro. Furthermore, treatment of PMN suspensions with cytokine-containing lung lavage fluid was found to enhance the bactericidal activity of PMN. The addition of anti-cachectin/TNF antibodies partially abrogated the stimulatory effects of the lavage fluid, suggesting that in vivo activation of PMN during the course of infection was likely, and that TNF was partially responsible for the enhanced bactericidal activity. In vivo treatment of animals with TNF resulted in significant protection of the animals from mortality. Furthermore, the rate of clearance of bacteria from the lung tissues of infected mice was increased in those animals treated with TNF, and correlated with the ability of this cytokine to protect the animals. These data suggest that the induction of TNF by Legionella bacteria during infection are involved in the non-specific host defense mechanisms, and that PMN activated by the TNF may be instrumental in clearing the organism from infected lung tissues, thereby protecting the animal.

Comparisons of several biological and physicochemical properties of human leukocyte interferons produced my human leukocytes and by E. coli.

Human interferon (IFN) prepared from virus-induced human leukocyte suspensions (leukocyte-derived interferon) was compared to the IFN extracted from Escherichia coli harboring a human interferon-alpha cDNA hybrid plasmid (Hif-SN35-AH-L6). E coli-derived IFN was 20 to 50 times more active than leukocyte-derived IFN on heterologous bovine, feline, murine and guinea pig cells, relative to the activity on human cells. After partial purification by affinity chromatography on an anti-human lymphoblastoid IFN antibody column, the IFN was analyzed by SDS-polyacrylamide gel electrophoresis. While leukocyte-derived IFN gave a heterogeneous pattern with major peaks of activity of 24000 and 19000 daltons, E. coli-derived IFN gave a heterogeneous peak of activity at about 17-18000 daltons. The leading edge of leukocyte-derived IFN in SDS-polyacrylamide gels was significantly more active on bovine cells than on human cells and coincided in mobility with E. coli-derived IFN, which was also much more active on bone than on human cells. After reduction with mercaptoethanol in SDS, the E. coli-derived IFN lost no activity, whereas the leukocyte-derived IFN lost about 90% of its activity. After reduction, E. coli-derived IFN migrated in SDS-polyacrylamide gels as a single peak at 24000 daltons, as did the residual activity of reduced leukocyte-derived interferon. Out data suggest that the interferon produced by the E. coli harboring the clone Hif-SN35-AH-L6 is analogous in size and cross-species activity to one of the molecular species of leukocyte-derived interferon.

Prediction of forced ventilation in animal fur from a measured pressure distribution.

A model and computation scheme are given for predicting forced ventilation in the fur on an animal limb or torso, modelled here as a fur-covered cylinder with the hairs erect. The intra-fur flow is described by an anisotropic Darcy model, and pressure distribution measured previously for flow past a solid cylinder at Reynolds number 1.29 x 10(5) is used for the outer flow. Calculations from the model are presented for five mammalian species.

Interferons: several questions and few answers.

Interferons, which have been studied for many years as antiviral agents, are now receiving considerable attention as antitumor and immunomodulatory agents. The data to date are sufficiently interesting to warrant further studies on several fronts. Clearly, the results that have been obtained so far tend to pose more questions than they answer.

Determination of human leukocyte populations involved in production of interferons alpha and gamma.

Human mononuclear leukocyte populations separated into T-, B-, and monocyte-enriched fractions, were evaluated for their abilities to produce interferons when induced with either virus, double-stranded RNA or mitogens. The main producer of alpha-interferon was the B-cell enriched subpopulation, but these cells did not produce gamma-interferon. In contrast, the T-cell enriched population produced either alpha or gamma interferons, depending upon the type of inducer used. The monocyte-enriched population was also able to produce either alpha or gamma interferon. The presence of monocytes in T-cell enriched populations enhanced the levels of alpha interferon production, and removal of monocytes from T-cell enriched populations diminished levels of alpha interferon produced. Even though each of the mononuclear populations (B-, T-, and monocytes) were able to produce alpha-interferon in response to poly rI.polyrC, it was found, by using a single-cell production assay, that only about 0.1% of the total mononuclear population actually produced alpha-interferon when so induced. Similarly, using the single-cell production assay, it was demonstrated that gamma-interferon was produced by only a small proportion of induced T-cells (possibly on T-cell subpopulation), as only about 1 T-cell per 1,000 responded to PHA by production of gamma-interferon.

Binding and capture of human interferon-alpha by reverse evaporation vesicles, multilamellar vesicles, and small unilamellar vesicles.

Liposomes of various physical and chemical compositions were prepared and their ability to externally bind and internally capture human interferon alpha (HuIFN-alpha) was determined. HuIFN-alpha was bound by preformed liposomes composed of either dipalmitoyl phosphatidyl choline alone or dipalmitoyl phosphatidic acid (calcium salt), and cholesterol, with or without a phosphatidyl choline component. HuIFN-alpha could also be internally captured within liposomes both of compositions that bound or did not bind interferon. The interferon could be associated with liposomes in at least three manners: bound to the outside surface of the liposome, associated partially within the liposomal membranes, or completely internalized either within the aqueous compartments of the liposome or completely buried within the liposomal bilayer membrane. HuIFN-alpha was stably-associated with reverse-evaporation vesicles, multilamellar vesicles, and small unilamellar vesicles for 30 days at 4 degrees C. Incubation of the multilamellar vesicles at 37 degrees C caused an initial decrease in the amount of externally bound interferon, and incubation with mouse serum caused a further dissociation of the externally-bound interferon. Depending on liposome composition, incubation at 37 degrees C either had little effect on stability of internalized interferon or caused leakage of internalized interferon.

Production and initial characterization of guinea pig interferon.

Guinea pig cell cultures produced extremely low levels of interferon when induced with Newcastle disease virus (NDV), or double-stranded RNA, poly rI.poly rC. Priming guinea pig cells with mouse interferon or guinea pig serum interferon did not significantly enhance interferon production. However, intracardial injection of 10(9) plaque forming units of NDV into guinea pigs lead to interferon production to levels over 6000 units per ml of serum 6 hr after the inducer was administered. The antiviral agent in the serum had the characteristics of interferon. Guinea pig interferon showed low levels of activity on mouse and bovine cells, and no detectable activity on human or rabbit cells.

Relative antiviral resistance induced in homologous and heterologous cells by cross-reacting interferons.

Human cells incubated with human interferon become more resistant to vesicular stomatitis virus (VSV) than to Semliki Forest virus (SFV); monkey cells treated with monkey interferon become more resistant to SFV than to VSV. However, monkey cells incubated with human interferon developed relative antiviral activity identical to that induced by homologous interferon, and human cells developed characteristic human interferon-induced relative antiviral activity when exposed to monkey interferon. Therefore, cross-reacting interferons induce the relative antiviral activity characteristic of the interferon-treated cell rather than the cell of the interferon's origin. This relationship supports the hypothesis that interferon is not itself antiviral but rather induces cells to develop their own antiviral activity.

Potentiation of the antiviral and anticellular activities of interferons by mixtures of HuIFN-gamma and HuIFN-alpha or HuIFN-beta.

Treatment of transformed human amnion WISH cells or human diploid fibroblasts (FS-4) or human fibroblasts trisomic for chromosome 21 (GM2767) with mixtures of human interferon gamma (HuIFN-gamma) and either natural leukocyte HuIFN-alpha or recombinant HuIFN alpha 2 or natural fibroblast HuIFN-beta resulted in potentiation of the antiviral activity of these IFNs. Pretreatment for 22 h of WISH cells with HuIFN-gamma followed by the addition of either HuIFN-alpha or HuIFN-beta resulted in significant potentiation of the antiviral action of these IFNs. The range of potentiation was 3 to 15-fold. Similar potentiation was observed when these IFNs were added simultaneously to the cells. Pretreatment for 22 h of WISH cells with either HuIFN-alpha or HuIFN-beta followed by the addition of HuIFN-gamma also resulted in significant increase of the antiviral protection against virus yield (3 to 39-fold). The level of the potentiation was higher in comparison with the antiviral activity observed when all these IFNs were added at the same time. Treatment of human FS-4 and GM2767 fibroblasts with HuIFN-gamma and either HuIFN-alpha or HuIFN-beta revealed potentiation of anticellular properties of these IFNs. The level of potentiation of anticellular activity was in the range of 2.7- to 9.4-fold. In the majority of the experiments, maximum potentiation of either antiviral or anti-cellular activity was observed when mixtures of equivalent concentrations of IFNs were used. The antiviral and anticellular functions of natural or recombinant IFN-alpha and fibroblast IFN-beta were potentiated usually to a similar degree by the presence of IFN-gamma. In contrast, combinations of HuIFN-alpha (natural or recombinant) and HuIFN-beta, in the absence of HuIFN-gamma, did not potentiate the anticellular or antiviral activity.

Parametric estimation of ventilation-perfusion ratio distributions.

We present a model and rigorous statistical approach for recovery of ventilation-perfusion ratio (V/Q) distribution parameters from multiple inert gas elimination data. We model the lung as a parallel combination of shunt, dead space, and one to three log-normal distributions of gas exchange units. This model provides a natural set of parameters for characterizing V/Q distributions. The log-normal terms are adjustable to represent smooth or sharp peaks in the distribution. Since the peak locations and widths are explicit in the model, very few parameters are needed. We select and estimate the significant parameters of the model by use of standard statistical tests and constrained least squares. This method provides two major advances in V/Q distribution estimation: 1) it allows flexible pooling and statistical comparisons of multiple experiments, and 2) it simultaneously gives both point estimates and 95% probability intervals for the V/Q distribution parameters. We present results of our procedure for data from humans in health, stress, and pulmonary disease. A program package, VQPAR, in FORTRAN is available for implementing the procedure.