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- Albert, A., et al.
(författare)
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SEARCHING FOR DARK MATTER ANNIHILATION IN RECENTLY DISCOVERED MILKY WAY SATELLITES WITH FERMI-LAT
- 2017
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 834:2
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Tidskriftsartikel (refereegranskat)abstract
- We search for excess gamma-ray emission coincident with the positions of confirmed and candidate Milky Way satellite galaxies using six years of data from the Fermi Large Area Telescope (LAT). Our sample of 45 stellar systems includes 28 kinematically confirmed dark-matter-dominated dwarf spheroidal galaxies (dSphs) and 17 recently discovered systems that have photometric characteristics consistent with the population of known dSphs. For each of these targets, the relative predicted gamma-ray flux due to dark matter annihilation is taken from kinematic analysis if available, and estimated from a distance-based scaling relation otherwise, assuming that the stellar systems are DM-dominated dSphs. LAT data coincident with four of the newly discovered targets show a slight preference (each similar to 2 sigma local) for gamma-ray emission in excess of the background. However, the ensemble of derived gamma-ray flux upper limits for individual targets is consistent with the expectation from analyzing random blank-sky regions, and a combined analysis of the population of stellar systems yields no globally significant excess (global significance < 1 sigma). Our analysis has increased sensitivity compared to the analysis of 15 confirmed dSphs by Ackermann et al. The observed constraints on the DM annihilation cross section are statistically consistent with the background expectation, improving by a factor of similar to 2 for large DM masses (m(DM, b<(b)over bar>) greater than or similar to 1 TeV and m(DM, tau+tau-) greater than or similar to 70 GeV) and weakening by a factor of similar to 1.5 at lower masses relative to previously observed limits.
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- Flesch, BK, et al.
(författare)
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Multicenter Study on Differential Human Neutrophil Antigen 2 Expression and Underlying Molecular Mechanisms
- 2020
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Ingår i: Transfusion medicine and hemotherapy : offizielles Organ der Deutschen Gesellschaft fur Transfusionsmedizin und Immunhamatologie. - : S. Karger AG. - 1660-3796. ; 47:5, s. 385-395
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Tidskriftsartikel (refereegranskat)abstract
- <b><i>Background:</i></b> The human neutrophil antigen 2 (HNA-2), which is expressed on CD177, is undetectable in 3–5% of the normal population. Exposure of these HNA-2<sub>null</sub> individuals to HNA-2-positive cells can cause immunization and production of HNA-2 antibodies, which can induce immune neutropenia and transfusion-related acute lung injury. In HNA-2-positive individuals, neutrophils are divided into a CD177<sup>pos.</sup> and a CD177<sup>neg.</sup> subpopulation. The molecular background of HNA-2 deficiency and the bimodal expression pattern, however, are not completely decoded. <b><i>Study Design:</i></b> An international collaboration was conducted on the genetic analysis of HNA-2-phenotyped blood samples, including HNA-2-deficient individuals, mothers, and the respective children with neonatal immune neutropenia and regular blood donors. <b><i>Results:</i></b> From a total of 54 HNA-2<sub>null</sub> individuals, 43 were homozygous for the <i>CD177</i>*<i>787A>T</i> substitution. Six carried the <i>CD177</i>*<i>c.1291G>A</i> single nucleotide polymorphism. All HNA-2-positive samples with >40% CD177<sup>pos.</sup> neutrophils carried the *<i>787A</i> wild-type allele, whereas a lower rate of CD177<sup>pos.</sup> neutrophils was preferentially associated with *<i>c.787AT</i> heterozygosity. Interestingly, only the *<i>c.787A</i> allele sequence was detected in complementary DNA (cDNA) sequence analysis carried out on all *<i>c.787AT</i> heterozygous individuals. However, cDNA analysis after sorting of CD177<sup>pos.</sup> and CD177<sup>neg.</sup> neutrophil subsets from HNA-2-positive individuals showed identical sequences, which makes regulatory elements within the promoter unlikely to affect <i>CD177</i> gene transcription in different CD177 neutrophil subsets. <b><i>Conclusion:</i></b> This comprehensive study clearly demonstrates the impact of single nucleotide polymorphisms on the expression of HNA-2 on the neutrophil surface but challenges the hypothesis of regulatory epigenetic effects being implicated in the bimodal CD177 expression pattern.
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