Delayed-Type hypersensitivity to latex: Computational prediction of MHC class II epitopes on latex allergens

Delayed type hypersensitivity to natural rubber latex is rare compared to IgE mediated immediate reactions. Binding of allergens to MHC Class II is a crucial step in the presentation of antigens to CD4+ T Cells responsible for delayed reactions. Computational prediction of MHC class II epitopes on thirteen known latex allergens using SMM-align method revealed strong binding with several alleles. This shows that latex allergens are capable of initiating delayed type hypersensitivity in susceptible individuals.
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Guinea pigs sublethally infected with aerosolized Legionella pneumophila develop humoral and cell-mediated immune responses and are protected against lethal aerosol challenge. A model for studying host defense against lung infections caused by intracellular pathogens.

We have employed the guinea pig model of L. pneumophila infection, which mimics Legionnaires' disease in humans both clinically and pathologically, to study humoral and cell-mediated immune responses to L. pneumophila and to examine protective immunity after aerosol exposure, the natural route of infection. Guinea pigs exposed to sublethal concentrations of L. pneumophila by aerosol developed strong humoral immune responses. By the indirect fluorescent antibody assay, exposed guinea pigs had a median serum antibody titer (expressed as the reciprocal of the highest positive dilution) of 32, whereas control guinea pigs had a median titer of less than 1. Sublethally infected (immunized) guinea pigs also developed strong cell-mediated immune responses. In response to L. pneumophila antigens, splenic lymphocytes from immunized but not control animals proliferated strongly in vitro, as measured by their capacity to incorporate [3H]thymidine. Moreover, immunized but not control guinea pigs developed strong cutaneous delayed-type hypersensitivity to intradermally injected L. pneumophila antigens. Sublethally infected (immunized) guinea pigs exhibited strong protective immunity to L. pneumophila. In two independent experiments, all 22 immunized guinea pigs survived aerosol challenge with one or three times the lethal dose of L. pneumophila whereas none of 16 sham-immunized control guinea pigs survived (p less than 0.0001 in each experiment). Immunized guinea pigs were not protected significantly from challenge with 10 times the lethal dose. Immunized but not control animals cleared the bacteria from their lungs. This study demonstrates that guinea pigs sublethally infected with L. pneumophila by the aerosol route develop strong humoral immune responses to this pathogen, develop strong cell-mediated immune responses and cutaneous delayed-type hypersensitivity to L. pneumophila antigens, are protected against subsequent lethal aerosol challenge, and are able to clear the bacteria from their lungs. The guinea pig model of L. pneumophila pulmonary infection is as an excellent one for studying general principles of host defense against pulmonary infections caused by intracellular pathogens

Tumor-derived exosomes confer antigen-specific immunosuppression in a murine delayed-type hypersensitivity model

Exosomes are endosome-derived small membrane vesicles that are secreted by most cell types including tumor cells. Tumor-derived exosomes usually contain tumor antigens and have been used as a source of tumor antigens to stimulate anti-tumor immune responses. However, many reports also suggest that tumor-derived exosomes can facilitate tumor immune evasion through different mechanisms, most of which are antigen-independent. In the present study we used a mouse model of delayed-type hypersensitivity (DTH) and demonstrated that local administration of tumor-derived exosomes carrying the model antigen chicken ovalbumin (OVA) resulted in the suppression of DTH response in an antigen-specific manner. Analysis of exosome trafficking demonstrated that following local injection, tumor-derived exosomes were internalized by CD11c+ cells and transported to the draining LN. Exosome-mediated DTH suppression is associated with increased mRNA levels of TGF-β1 and IL-4 in the draining LN. The tumor-derived exosomes examined were also found to inhibit DC maturation. Taken together, our results suggest a role for tumor-derived exosomes in inducing tumor antigen-specific immunosuppression, possibly by modulating the function of APCs. © 2011 Yang et al

Large lepton asymmetry from Q-balls

We propose a scenario which can explain large lepton asymmetry and small baryon asymmetry simultaneously. Large lepton asymmetry is generated through Affleck-Dine (AD) mechanism and almost all the produced lepton numbers are absorbed into Q-balls (L-balls). If the lifetime of the L-balls is longer than the onset of electroweak phase transition but shorter than the epoch of big bang nucleosynthesis (BBN), the large lepton asymmetry in the L-balls is protected from sphaleron effects. On the other hand, small (negative) lepton numbers are evaporated from the L-balls due to thermal effects, which are converted into the observed small baryon asymmetry by virtue of sphaleron effects. Large and positive lepton asymmetry of electron type is often requested from BBN. In our scenario, choosing an appropriate flat direction in the minimal supersymmetric standard model (MSSM), we can produce positive lepton asymmetry of electron type but totally negative lepton asymmetry.Comment: 10 pages, 3 figures, ReVTeX

General Relativistic White Dwarfs and Their Astrophysical Implications

We consider applications of general relativistic uniformly-rotating white dwarfs to several astrophysical phenomena related to the spin-up and the spin-down epochs and to delayed type Ia supernova explosions of super-Chandrasekhar white dwarfs, where we estimate the "spinning down" lifetime due to magnetic-dipole braking. In addition, we describe the physical properties of Soft Gamma Repeaters and Anomalous X-Ray Pulsars as massive rapidly-rotating highly-magnetized white dwarfs. Particularly we consider one of the so-called low-magnetic-field magnetars SGR 0418+5729 as a massive rapidly-rotating highly-magnetized white dwarf and give bounds for the mass, radius, moment of inertia, and magnetic field by requiring the general relativistic uniformly-rotating configurations to be stable.Comment: 13 pages, 4 figures. arXiv admin note: text overlap with arXiv:1204.207

A unique model for the variety of multiple populations formation(s) in globular clusters: a temporal sequence

We explain the multiple populations recently found in the 'prototype' Globular Cluster (GC) NGC 2808 in the framework of the asymptotic giant branch (AGB) scenario. The chemistry of the five -or more- populations is approximately consistent with a sequence of star formation events, starting after the supernovae type II epoch, lasting approximately until the time when the third dredge up affects the AGB evolution (age ~90-120Myr), and ending when the type Ia supernovae begin exploding in the cluster, eventually clearing it from the gas. The formation of the different populations requires episodes of star formation in AGB gas diluted with different amounts of pristine gas. In the nitrogen-rich, helium-normal population identified in NGC 2808 by the UV Legacy Survey of GCs, the nitrogen increase is due to the third dredge up in the smallest mass AGB ejecta involved in the star formation of this population. The possibly-iron-rich small population in NGC 2808 may be a result of contamination by a single type Ia supernova. The NGC 2808 case is used to build a general framework to understand the variety of 'second generation' stars observed in GCs. Cluster-to-cluster variations are ascribed to differences in the effects of the many processes and gas sources which may be involved in the formation of the second generation. We discuss an evolutionary scheme, based on pollution by delayed type II supernovae, which accounts for the properties of s-Fe-anomalous clusters.Comment: 20 pages, 7 figures, in press on MNRA

Determination of susceptibility to sensitization to dental materials in atopic and non-atopic patients

Introduction: Some studies report that atopic patients have a greater frequency of delayed-type sensitization than non-atopic patients. Objective: To determine the influence of the atopic condition on delayed sensitization to dental materials. Design: cross-sectional study. Methods: Forty (40) atopic subjects and forty (40) non-atopic subjects, of both sexes, between 20 and 65 years of age were included. The determination of delayed sensitization to dental materials was performed using patch test. An oral exam was also carried out to check for lesions of the oral mucosa. Results: 61.25% of the patients were positive for delayed-type sensitization to one or more allergens, being palladium chloride (21.25%), ammoniated mercury (20%), benzoyl peroxide (12.5%) and amalgam (10%) the most frequent. The frequency of sensitization was 67.5% in the group of atopic patients, compared to 55% in the non atopic group (p>0.05). The materials with the greatest difference of sensitization in atopic compared to non-atopic patients were ammoniated mercury, benzoyl peroxide, amalgam and Bisphenol A Dimethacrylate (BIS-GMA). Conclusion: The atopic condition is not related to a higher frequency of delayed sensitization to a battery of dental materials. © Medicina Oral