Polyclonal mucosa-associated invariant T cells have unique innate functions in bacterial infection

Mucosa-associated invariant T (MAIT) cells are a unique population of αβ T cells in mammals that reside preferentially in mucosal tissues and express an invariant Vα paired with limited Vβ T-cell receptor (TCR) chains. Furthermore, MAIT cell development is dependent upon the expression of the evolutionarily conserved major histocompatibility complex (MHC) class Ib molecule MR1. Using in vitro assays, recent studies have shown that mouse and human MAIT cells are activated by antigen-presenting cells (APCs) infected with diverse microbes, including numerous bacterial strains and yeasts, but not viral pathogens. However, whether MAIT cells play an important, and perhaps unique, role in controlling microbial infection has remained unclear. To probe MAIT cell function, we show here that purified polyclonal MAIT cells potently inhibit intracellular bacterial growth of Mycobacterium bovis BCG in macrophages (MΦ) in coculture assays, and this inhibitory activity was dependent upon MAIT cell selection by MR1, secretion of gamma interferon (IFN-γ), and an innate interleukin 12 (IL-12) signal from infected MΦ. Surprisingly, however, the cognate recognition of MR1 by MAIT cells on the infected MΦ was found to play only a minor role in MAIT cell effector function. We also report that MAIT cell-deficient mice had higher bacterial loads at early times after infection compared to wild-type (WT) mice, demonstrating that MAIT cells play a unique role among innate lymphocytes in protective immunity against bacterial infection

A novel role of dendritic gap junction and mechanisms underlying its interaction with thalamocortical conductance in fast spiking inhibitory neurons

<p>Abstract</p> <p>Background</p> <p>Little is known about the roles of dendritic gap junctions (GJs) of inhibitory interneurons in modulating temporal properties of sensory induced responses in sensory cortices. Electrophysiological dual patch-clamp recording and computational simulation methods were used in combination to examine a novel role of GJs in sensory mediated feed-forward inhibitory responses in barrel cortex layer IV and its underlying mechanisms.</p> <p>Results</p> <p>Under physiological conditions, excitatory post-junctional potentials (EPJPs) interact with thalamocortical (TC) inputs within an unprecedented few milliseconds (i.e. over 200 Hz) to enhance the firing probability and synchrony of coupled fast-spiking (FS) cells. Dendritic GJ coupling allows fourfold increase in synchrony and a significant enhancement in spike transmission efficacy in excitatory spiny stellate cells. The model revealed the following novel mechanisms: <b><it>1) </it></b>rapid capacitive current (I_cap) underlies the activation of voltage-gated sodium channels; <b><it>2) </it></b>there was less than 2 milliseconds in which the I_capunderlying TC input and EPJP was coupled effectively; <b><it>3) </it></b>cells with dendritic GJs had larger input conductance and smaller membrane response to weaker inputs; <b><it>4) </it></b>synchrony in inhibitory networks by GJ coupling leads to reduced sporadic lateral inhibition and increased TC transmission efficacy.</p> <p>Conclusion</p> <p>Dendritic GJs of neocortical inhibitory networks can have very powerful effects in modulating the strength and the temporal properties of sensory induced feed-forward inhibitory and excitatory responses at a very high frequency band (>200 Hz). Rapid capacitive currents are identified as main mechanisms underlying interaction between two transient synaptic conductances.</p

The dynamics of oxygen concentration, pH value, and organic acids in the rhizosphere of Juncus spp.

A novel type of planar optodes for simultaneous optical analysis of pH and oxygen dynamics in the rhizosphere is introduced. The combination of the optical, non-invasive measurement of these parameters with sterile sampling of rhizosphere solution across and along growing roots by use of a novel type of rhizobox provides a methodical step forward in the investigation of the physicochemical dynamics of the rhizosphere and its underlying matter fluxes between roots and soil. In this study, this rhizobox was used to investigate the effect of oxygen releasing roots of three Juncus species on the amount and distribution of organic acids in reductive, oxygen-deficient soils of different pH (pH 3.9-pH 5.9). Pronounced diurnal variations of oxygen concentration and pH along the roots, particularly along the elongation zone were observed. Long-term records over more than eight weeks revealed considerable spatial and temporal patterns of oxygen over a range of almost 200 mu mol O-2 L-1 and pH dynamics of +/- 1.4 pH units in the rhizosphere. A strong effect of oxidative acidification due to oxygen release by the plant roots was clearly visible for Juncus effusus, whereas the roots of Juncus articulatus alkalinized the rhizosphere. In contrast, roots of Juncus inflexus induced no effects on rhizospheric pH. Only four different organic acids (oxalate, acetate, formate and lactate) were detectable in all soil solutions. Maximal concentration of all organic acids occurred at pH 3.9, whereas the lowest concentration of each organic acid was found at pH 5.9. Hence, considering the pH-dependence of the redox potential, the acid soil provided increased reductive conditions leading to slower anaerobic degradation of organic acids to CO2 or methane (CH4). The concentration of organic acids decreased by up to 58% within a distance of only 4 mm from the bulk soil to the root surface, i.e. reciprocal to the pronounced O-2-gradient. The decreasing presence of organic acids toward the oxygen releasing roots is possibly due to a change in the composition of the microbial community from anaerobic to aerobic conditions. The present study highlights the dynamic interplay between O-2 concentration, pH and organic acids as key parameters of the physicochemical environment of the rhizosphere, particularly for wetland plants growing in oxygen-deficient waterlogged soils. (C) 2011 Elsevier Ltd. All rights reserved