Legionella pneumophila induces human beta Defensin-3 in pulmonary cells

<p>Abstract</p> <p>Background</p> <p><it>Legionella pneumophila </it>is an important causative agent of severe pneumonia in humans. Human alveolar epithelium and macrophages are effective barriers for inhaled microorganisms and actively participate in the initiation of innate host defense. The beta defensin-3 (hBD-3), an antimicrobial peptide is an important component of the innate immune response of the human lung. Therefore we hypothesize that hBD-3 might be important for immune defense towards <it>L. pneumophila</it>.</p> <p>Methods</p> <p>We investigated the effects of <it>L. pneumophila </it>and different TLR agonists on pulmonary cells in regard to hBD-3 expression by ELISA. Furthermore, siRNA-mediated inhibition of TLRs as well as chemical inhibition of potential downstream signaling molecules was used for functional analysis.</p> <p>Results</p> <p><it>L. pneumophila </it>induced release of hBD-3 in pulmonary epithelium and alveolar macrophages. A similar response was observed when epithelial cells were treated with different TLR agonists. Inhibition of TLR2, TLR5, and TLR9 expression led to a decreased hBD-3 expression. Furthermore expression of hBD-3 was mediated through a JNK dependent activation of AP-1 (c-Jun) but appeared to be independent of NF-κB. Additionally, we demonstrate that hBD-3 elicited a strong antimicrobial effect on <it>L. pneumophila </it>replication.</p> <p>Conclusions</p> <p>Taken together, human pulmonary cells produce hBD-3 upon <it>L. pneumophila </it>infection via a TLR-JNK-AP-1-dependent pathway which may contribute to an efficient innate immune defense.</p

Pattern recognition receptors in immune disorders affecting the skin.

Contains fulltext : 109004.pdf (publisher's version ) (Open Access)Pattern recognition receptors (PRRs) evolved to protect organisms against pathogens, but excessive signaling can induce immune responses that are harmful to the host. Putative PRR dysfunction is associated with numerous immune disorders that affect the skin, such as systemic lupus erythematosus, cryopyrin-associated periodic syndrome, and primary inflammatory skin diseases including psoriasis and atopic dermatitis. As yet, the evidence is often confined to genetic association studies without additional proof of a causal relationship. However, insight into the role of PRRs in the pathophysiology of some disorders has already resulted in new therapeutic approaches based on immunomodulation of PRRs

Antarctic HF radar observations of irregularities associated with polar patches and auroral blobs: A case study

We report a case study of decameter-scale electron density irregularities associated with polar cap patches and auroral (boundary) blobs in the southern high-latitude F region ionosphere. The observations were carried out on July 14, 1995, with the Antarctic Super Dual Auroral Radar Network HF radars located at Syowa Station and Halley. On that day, 17 irregularity events associated with the patches were identified in the polar cap. The time distribution of these events is consistent with previous model calculations of patch formation and transportation in the northern hemisphere for southward interplanetary magnetic field (IMF) conditions (Bz 0). These patches seem to have been transported into the polar cap from the dayside cusp where the patches had been generated under negative Bz conditions. The striated radar echo patterns due to a series of auroral blobs, clearly observed at Halley in the evening auroral zone, are well explained by previous simulations that calculated the time evolution and transportation of a patch initially located in the polar cap

Seasonal influence on polar cap patches in the high-latitude nightside ionosphere

The influence of the season on the patch-to-background density ratio of polar cap patches in the nightside ionosphere was observed above northern Scandinavia around solar maximum (1999–2001). This is the first study of the seasonal effect in the nightside polar ionosphere. The observations were conducted by the European Incoherent Scatter Svalbard Radar under conditions favorable for patches based on the high-latitude plasma convection pattern, the interplanetary magnetic field, and an absence of in situ precipitation. Patch-to-background ratios of up to 9.4 ± 2.9 were observed between midwinter and equinox, with values of up to 1.9 ± 0.2 in summer. As the patch-to-background ratios in summer were <2, the enhancements could not formally be called patches; however, these were significant density enhancements within the antisunward cross-polar flow. Aberystwyth University's PLASLIFE (PLASma LIFEtime) computer simulation was used to model the observed seasonal trend in the patch-to-background ratio and to establish reasons for the difference between winter and summer values. This difference was primarily attributed to variation in the chemical composition of the atmosphere, which, in summer, both reduced the electron densities of the plasma drawn into the polar cap on the dayside and enhanced plasma loss by recombination. A secondary factor was the maintenance of the background polar ionosphere by photoionization in summer

Ionospheric convection response to slow, strong variations in a northward interplanetary magnetic field: A case study for January 14, 1988

We analyze ionospheric convection patterns over the polar regions during the passage of an interplanetary magnetic cloud on January 14, 1988, when the interplanetary magnetic field (IMF) rotated slowly in direction and had a large amplitude. Using the assimilative mapping of ionospheric electrodynamics (AMIE) procedure, we combine simultaneous observations of ionospheric drifts and magnetic perturbations from many different instruments into consistent patterns of high-latitude electrodynamics, focusing on the period of northward IMF. By combining satellite data with ground-based observations, we have generated one of the most comprehensive data sets yet assembled and used it to produce convection maps for both hemispheres. We present evidence that a lobe convection cell was embedded within normal merging convection during a period when the IMF By and Bz components were large and positive. As the IMF became predominantly northward, a strong reversed convection pattern (afternoon-to-morning potential drop of around 100 kV) appeared in the southern (summer) polar cap, while convection in the northern (winter) hemisphere became weak and disordered with a dawn-to-dusk potential drop of the order of 30 kV. These patterns persisted for about 3 hours, until the IMF rotated significantly toward the west. We interpret this behavior in terms of a recently proposed merging model for northward IMF under solstice conditions, for which lobe field lines from the hemisphere tilted toward the Sun (summer hemisphere) drape over the dayside magnetosphere, producing reverse convection in the summer hemisphere and impeding direct contact between the solar wind and field lines connected to the winter polar cap. The positive IMF Bx component present at this time could have contributed to the observed hemispheric asymmetry. Reverse convection in the summer hemisphere broke down rapidly after the ratio |By/Bz| exceeded unity, while convection in the winter hemisphere strengthened. A dominant dawn-to-dusk potential drop was established in both hemispheres when the magnitude of By exceeded that of Bz, with potential drops of the order of 100 kV, even while Bz remained northward. The later transition to southward Bz produced a gradual intensification of the convection, but a greater qualitative change occurred at the transition through |By/Bz| = 1 than at the transition through Bz = 0. The various convection patterns we derive under northward IMF conditions illustrate all possibilities previously discussed in the literature: nearly single-cell and multicell, distorted and symmetric, ordered and unordered, and sunward and antisunward

HF propagation modeling within the polar ionosphere

This paper illustrates the importance of understanding and taking into account the presence of various structural features in the polar ionosphere (in particular, patches and arcs of enhanced electron density) when planning and operating HF radio links. These features result in radio waves propagating over paths well displaced from the great circle direction and impact on almost any HF communications system where the signal reflects from the ionosphere within the region poleward of the subauroral trough. The off–great circle mechanisms give rise to propagation at times that are not predicted by current prediction codes and may also suppress propagation at times that are expected. Techniques to account for this type of propagation are therefore required. A ray-tracing model that accurately reproduces many of the direction of arrival features observed in experimental measurements has been developed. Particular attention will be given in this paper to area coverage estimations undertaken by means of the ray-tracing model

Riometer and HF radar signatures of polar patches

Polar patch was the name given originally to a spatially limited enhancement of the 630-nm emission observed in the dark polar cap. More recently, the term has been applied to related phenomena observed by other experimental techniques. The interrelationship between patches observed by differing methods has yet to be determined fully. In this paper the signatures of a series of polar patches observed by Halley HF radar and the South Pole broad-beam and imaging riometers are presented. Most frequently, the HF radar patch signature immediately precedes that of the riometer polar patch signature. The interpretation is that the leading edge of the electron concentration structure that forms the patch is steeper than its trailing edge. On a few occasions, HF radar polar patch signatures coincide with the trailing edge of riometer patches and sometimes are seen throughout the riometer patch. Halley digital ionosonde data are used to show that riometer patches are more common over South Pole when the maximum F region plasma concentration is considerably in excess of 5×1011 m−3, which often occurs in the afternoon plasma convection cell