93 research outputs found
Interactions between fibroblastic reticular cells and B cells promote mesenteric lymph node lymphangiogenesis.
Lymphatic growth (lymphangiogenesis) within lymph nodes functions to promote dendritic cell entry and effector lymphocyte egress in response to infection or inflammation. Here we demonstrate a crucial role for lymphotoxin-beta receptor (LTβR) signaling to fibroblastic reticular cells (FRCs) by lymphotoxin-expressing B cells in driving mesenteric lymph node lymphangiogenesis following helminth infection. LTβR ligation on fibroblastic reticular cells leads to the production of B-cell-activating factor (BAFF), which synergized with interleukin-4 (IL-4) to promote the production of the lymphangiogenic factors, vascular endothelial growth factors (VEGF)-A and VEGF-C, by B cells. In addition, the BAFF-IL-4 synergy augments expression of lymphotoxin by antigen-activated B cells, promoting further B cell-fibroblastic reticular cell interactions. These results underlie the importance of lymphotoxin-dependent B cell-FRC cross talk in driving the expansion of lymphatic networks that function to promote and maintain immune responsiveness.The growth of lymph nodes in response to infection requires lymphangiogenesis. Dubey et al. show that the mesenteric lymph node lymphangiogenesis upon helminth infection depends on the signaling loop between the B and fibroblastic reticular cells (FRCs), whereby the FRCs respond to lymphotoxin secreted by B cells by releasing B cell activating factor
Treatment of ongoing autoimmune encephalomyelitis with activated B-cell progenitors maturing into regulatory B cells.
The influence of signals perceived by immature B cells during their development in bone marrow on their subsequent functions as mature cells are poorly defined. Here, we show that bone marrow cells transiently stimulated in vivo or in vitro through the Toll-like receptor 9 generate proB cells (CpG-proBs) that interrupt experimental autoimmune encephalomyelitis (EAE) when transferred at the onset of clinical symptoms. Protection requires differentiation of CpG-proBs into mature B cells that home to reactive lymph nodes, where they trap T cells by releasing the CCR7 ligand, CCL19, and to inflamed central nervous system, where they locally limit immunopathogenesis through interleukin-10 production, thereby cooperatively inhibiting ongoing EAE. These data demonstrate that a transient inflammation at the environment, where proB cells develop, is sufficient to confer regulatory functions onto their mature B-cell progeny. In addition, these properties of CpG-proBs open interesting perspectives for cell therapy of autoimmune diseases
Pairing and Phase Coherence in High Temperature Superconductors
Mobile holes in an antiferromagnetic insulator form a slowly fluctuating
array of quasi one-dimensional metallic stripes, which induce a spin gap or
pseudogap in the intervening Mott-insulating regions. The mobile holes on an
individual stripe acquire a spin gap via pair hopping between the stripe and
its environment; i.e. via a magnetic analog of the usual superconducting
proximity effect. This process is the analog of pairing in conventional
superconductors. At non-vanishing stripe densities, Josephson coupling between
stripes produces a dimensional crossover to a state with long-range
superconducting phase coherence. In contrast to conventional superconductors,
the superconducting state is characterised by a high density of (spin) pairs,
but the phase stiffness, which is determined by the density and mobility of
holes on the stripes, is very low.Comment: 4 pages. Proceedings of MMS-High Temperature Superconductivity, V
(1997) To be published in Physica
Interacting one dimensional electron gas with open boundaries
We discuss the properties of interacting electrons on a finite chain with
open boundary conditions. We extend the Haldane Luttinger liquid description to
these systems and study how the presence of the boundaries modifies various
correlation functions. In view of possible experimental applications to quantum
wires, we analyse how tunneling measurements can reveal the underlying
Luttinger liquid properties. The two terminal conductance is calculated. We
also point out possible applications to quasi one dimensional materials and
study the effects of magnetic impurities.Comment: 38 pages, ReVTeX, 7 figures (available upon request
Lattice vibrations of alpha'-NaV_2O_5 in the low-temperature phase. Magnetic bound states?
We report high resolution polarized infrared studies of the quarter-filled
spin ladder compound alpha'-NaV_2O_5 as a function of temperature (5K <= T <=
300K). Numerous new modes were detected below the temperature T_c=34K of the
phase transition into a charge ordered nonmagnetic state accompanied by a
lattice dimerization. We analyse the Brillouin zone (BZ) folding due to lattice
dimerization at T_c and show that some peculiarities of the low-temperature
vibrational spectrum come from quadruplets folded from the BZ point (1/2, 1/2,
1/4). We discuss an earlier interpretation of the 70, 107, and 133cm-1 modes as
magnetic bound states and propose the alternative interpretation as folded
phonon modes strongly interacting with charge and spin excitations.Comment: 15 pages, 13 Postscript figure
Using electronic structure changes to map the H-T phase diagram of alpha'-NaV2O5
We report polarized optical reflectance studies of \alpha'-NaV2O5 as a
function of temperature (4-45 K) and magnetic field (0-60 T). Rung directed
electronic structure changes, as measured by near-infrared reflectance ratios
\Delta R(H)=R(H)/R(H=0 T), are especially sensitive to the phase boundaries. We
employ these changes to map out an H-T phase diagram. Topological highlights
include the observation of two phase boundaries slightly below T_{SG}, enhanced
curvature of the 34 K phase boundary above 35 T, and, surprisingly, strong
hysteresis effects of both transitions with applied field.Comment: 4 pages, 3 figures, PRB accepte
X-wave mediated instability of plane waves in Kerr media
Plane waves in Kerr media spontaneously generate paraxial X-waves (i.e.
non-dispersive and non-diffractive pulsed beams) that get amplified along
propagation. This effect can be considered a form of conical emission (i.e.
spatio-temporal modulational instability), and can be used as a key for the
interpretation of the out of axis energy emission in the splitting process of
focused pulses in normally dispersive materials. A new class of spatio-temporal
localized wave patterns is identified. X-waves instability, and nonlinear
X-waves, are also expected in periodical Bose condensed gases.Comment: 4 pages, 6 figure
Condensed matter and AdS/CFT
I review two classes of strong coupling problems in condensed matter physics,
and describe insights gained by application of the AdS/CFT correspondence. The
first class concerns non-zero temperature dynamics and transport in the
vicinity of quantum critical points described by relativistic field theories. I
describe how relativistic structures arise in models of physical interest,
present results for their quantum critical crossover functions and
magneto-thermoelectric hydrodynamics. The second class concerns symmetry
breaking transitions of two-dimensional systems in the presence of gapless
electronic excitations at isolated points or along lines (i.e. Fermi surfaces)
in the Brillouin zone. I describe the scaling structure of a recent theory of
the Ising-nematic transition in metals, and discuss its possible connection to
theories of Fermi surfaces obtained from simple AdS duals.Comment: 39 pages, 12 figures; Lectures at the 5th Aegean summer school, "From
gravity to thermal gauge theories: the AdS/CFT correspondence", and the De
Sitter Lecture Series in Theoretical Physics 2009, University of Groninge
Sliding Luttinger liquid phases
We study systems of coupled spin-gapped and gapless Luttinger liquids. First,
we establish the existence of a sliding Luttinger liquid phase for a system of
weakly coupled parallel quantum wires, with and without disorder. It is shown
that the coupling can {\it stabilize} a Luttinger liquid phase in the presence
of disorder. We then extend our analysis to a system of crossed Luttinger
liquids and establish the stability of a non-Fermi liquid state: the crossed
sliding Luttinger liquid phase (CSLL). In this phase the system exhibits a
finite-temperature, long-wavelength, isotropic electric conductivity that
diverges as a power law in temperature as . This two-dimensional
system has many properties of a true isotropic Luttinger liquid, though at zero
temperature it becomes anisotropic. An extension of this model to a
three-dimensional stack exhibits a much higher in-plane conductivity than the
conductivity in a perpendicular direction.Comment: Revtex, 18 pages, 8 figure
Generalized Spectral Signatures of Electron Fractionalization in Quasi-One and -Two Dimensional Molybdenum Bronzes and Superconducting Cuprates
We establish the quasi-one-dimensional Li purple bronze as a photoemission
paradigm of Luttinger liquid behavior. We also show that generalized signatures
of electron fractionalization are present in the angle resolved photoemission
spectra for quasi-two-dimensional purple bronzes and certain cuprates. An
important component of our analysis for the quasi-two-dimensional systems is
the proposal of a ``melted holon'' scenario for the k-independent background
that accompanies but does not interact with the peaks that disperse to define
the Fermi surface.Comment: 7 pages, 8 figure
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