In Situ Formation of Free-Standing Single-Atom-Thick Antiferromagnetic Chromium Membranes.

Compared to van der Waals two-dimensional (2D) layers with lateral covalent bonds, metallic bonding systems favor close-packed structures, and thus, free-standing 2D metals have remained, for the most part, elusive. However, a number of theoretical studies suggest a number of metals can exist as 2D materials and a few early experiments support this notion. Here we demonstrate free-standing single-atom-thick crystalline chromium (Cr) suspended membranes using aberration-corrected transmission electron microscopy and image simulations. Density functional theory studies confirm the 2D Cr membranes have an antiferromagnetic ground state making them highly attractive for spintronic applications. Moreover, the work also helps consolidate the existence of a new family of 2D metal layers.

Ripk3 licenced protection against microbial infection in the absence of Caspase1-11 inflammasome.

Receptor interacting protein kinase 3 (Ripk3) is a signal relay protein involved in initiation of programmed cell death (necroptosis) and modulation of inflammasome activation. While caspase 1 and 11 are pro-inflammatory caspases responsible for unleashing inflammation and cell death by enzymatic activation of the executioners of inflammation and cell death (pyroptosis). Upon Salmonella infection, the host mounts a pro-inflammatory response which require Ripk3 and Caspase1/11. Here we show that bone marrow derived macrophages with combined deficiency of Ripk3 and Casp1/11 are highly resistant to Salmonella induced cell death, and that these macrophages show an anti-inflammatory cytokine profile. We confirm what was previously known that mice deficient in Casp1/11 have impaired ability to control Salmonella burden, and that the absence of Ripk3 alone does not influence the innate immune responses to Salmonella infection. However, we describe a synergistic role of Ripk3 and Casp1/11 in regulating Salmonella in vivo burden and that Ripk3-dependent host protection in the absence of Casp1/11 is evident during infection by sifA-expressing Salmonella. In summary, we show that the Ripk3 protection to Salmonella infection is obscured by presence of Caspase 1/11 and that the Ripk3-dependent protection requires a phagosome-bound Salmonella.

Culling of APCs by inflammatory cell death pathways restricts TIM3 and PD-1 expression and promotes the survival of primed CD8 T cells.

We evaluated the impact of premature cell death of antigen-presenting cells (APCs) by Caspase-1- and RipK3-signaling pathways on CD8+ T-cell priming during infection of mice with Salmonella typhimurium (ST). Our results indicate that Caspase1 and RipK3 synergize to rapidly eliminate infected APCs, which does not influence the initial activation of CD8+ T cells. However, the maintenance of primed CD8+ T cells was greatly compromised when both these pathways were disabled. Caspase-1- and RipK3-signaling did not influence NF-κB signaling in APCs, but synergized to promote processing of IL-1 and IL-18. Combined deficiency of Caspase1 and RipK3 resulted in compromised innate immunity and accelerated host fatality due to poor processing of IL-18. In contrast, synergism in cell death by Caspase-1- and RipK3 resulted in restriction of PD-1 and TIM3 expression on primed CD8+ T cells, which promoted the survival of activated CD8+ T cells.

The Heterogeneity of Ly6Chi Monocytes Controls Their Differentiation into iNOS+ Macrophages or Monocyte-Derived Dendritic Cells.

Inflammation triggers the differentiation of Ly6Chi monocytes into microbicidal macrophages or monocyte-derived dendritic cells (moDCs). Yet, it is unclear whether environmental inflammatory cues control the polarization of monocytes toward each of these fates or whether specialized monocyte progenitor subsets exist before inflammation. Here, we have shown that naive monocytes are phenotypically heterogeneous and contain an NR4A1- and Flt3L-independent, CCR2-dependent, Flt3+CD11c-MHCII+PU.1hi subset. This subset acted as a precursor for FcγRIII+PD-L2+CD209a+, GM-CSF-dependent moDCs but was distal from the DC lineage, as shown by fate-mapping experiments using Zbtb46. By contrast, Flt3-CD11c-MHCII-PU.1lo monocytes differentiated into FcγRIII+PD-L2-CD209a-iNOS+ macrophages upon microbial stimulation. Importantly, Sfpi1 haploinsufficiency genetically distinguished the precursor activities of monocytes toward moDCs or microbicidal macrophages. Indeed, Sfpi1+/- mice had reduced Flt3+CD11c-MHCII+ monocytes and GM-CSF-dependent FcγRIII+PD-L2+CD209a+ moDCs but generated iNOS+ macrophages more efficiently. Therefore, intercellular disparities of PU.1 expression within naive monocytes segregate progenitor activity for inflammatory iNOS+ macrophages or moDCs.

Dependence of Raman Spectral Intensity on Crystal Size in Organic Nano Energetics.

Raman spectra for various nitramine energetic compounds were investigated as a function of crystal size at the nanoscale regime. In the case of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20), there was a linear relationship between intensity of Raman spectra and crystal size. Notably, the Raman modes between 120 cm(-1) and 220 cm(-1) were especially affected, and at the smallest crystal size, were completely eliminated. The Raman spectral intensity of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), like that of CL-20's, depended linearly on crystal size. The Raman spectral intensity of 1,3,5-trinitroperhydro-1,3,5-triazine (RDX), however, was not observably changed by crystal size. A non-nitramine explosive compound, 2,4,6-triamino-1,3,5- trinitrobenzene (TATB), was also investigated. Its spectral intensity was also found to correlate linearly with crystal size, although substantially less so than that of HMX and CL-20. To explain the observed trends, it is hypothesized that disordered molecular arrangement, originating from the crystal surface, may be responsible. In particular, it appears that the thickness of the disordered surface layer is dependent on molecular characteristics, including size and conformational flexibility. Furthermore, as the mean crystal size decreases, the volume fraction of disordered molecules within a specimen increases, consequently, weakening the Raman intensity. These results could have practical benefit for allowing the facile monitoring of crystal size during manufacturing. Finally, these findings could lead to deep insights into the general structure of the surface of crystals.

Boron-Filled Hybrid Carbon Nanotubes.

A unique nanoheterostructure, a boron-filled hybrid carbon nanotube (BHCNT), has been synthesized using a one-step chemical vapor deposition process. The BHCNTs can be considered to be a novel form of boron carbide consisting of boron doped, distorted multiwalled carbon nanotubes (MWCNTs) encapsulating boron nanowires. These MWCNTs were found to be insulating in spite of their graphitic layered outer structures. While conventional MWCNTs have great axial strength, they have weak radial compressive strength, and do not bond well to one another or to other materials. In contrast, BHCNTs are shown to be up to 31% stiffer and 233% stronger than conventional MWCNTs in radial compression and have excellent mechanical properties at elevated temperatures. The corrugated surface of BHCNTs enables them to bond easily to themselves and other materials, in contrast to carbon nanotubes (CNTs). BHCNTs can, therefore, be used to make nanocomposites, nanopaper sheets, and bundles that are stronger than those made with CNTs.

Transcription factor Batf3 is important for development of CD8+ T-cell response against a phagosomal bacterium regardless of the location of antigen.

Salmonella enterica serovar Typhimurium (ST) is a virulent intracellular bacterium that conceals itself in the phagosomes of infected cells. Although CD8(+) T cells promote protection against various intracellular pathogens, the role of CD8(+) T cells against virulent ST has been unclear due to early fatality of susceptible (B6) mice. Herein, we generated MHC I-deficient mice on the resistant (129SvJ) and susceptible (Nramp1 transgenic B6) background to evaluate the role of CD8(+) T cells against virulent ST. Our results indicate that CD8(+) T cells have a critical protective role in host survival during infection with virulent ST. As antigen presentation and CD8(+) T-cell activation against phagosomal antigens are considered to operate through the cross-presentation pathway, we have evaluated CD8(+) T-cell response against ST in Batf3-deficient mice that lack CD8α dendritic cells (DCs). Using a recombinant of ST that expresses antigen (ST-OVA) mainly in the phagosomes of infected cells, we show that CD8(+) T-cell response is compromised throughout the duration of infection in Batf3-deficient mice. In contrast, when ST delivers antigen to the cytosol of infected cells (ST-OVA-C), CD8(+) T-cell response against the cytosolic antigen was compromised only in the short term in the absence of CD8α DCs, with wild-type and Batf3-deficient mice generating similar CD8(+) T-cell response in the long term. Thus, Batf3 has an important role in CD8(+) T-cell priming regardless of antigenic location; however, its role is redundant at later time intervals against cytosolic antigen.

Radiation oncology: physics advances that minimize morbidity.

Radiation therapy has become an ever more successful treatment for many cancer patients. This is due in large part from advances in physics including the expanded use of imaging protocols combined with ever more precise therapy devices such as linear and particle beam accelerators, all contributing to treatments with far fewer side effects. This paper will review current state-of-the-art physics maneuvers that minimize morbidity, such as intensity-modulated radiation therapy, volummetric arc therapy, image-guided radiation, radiosurgery and particle beam treatment. We will also highlight future physics enhancements on the horizon such as MRI during treatment and intensity-modulated hadron therapy, all with the continued goal of improved clinical outcomes.

Future radiation therapy: photons, protons and particles.

Radiation therapy plays a critical role in the current management of cancer patients. The most common linear accelerator-based treatment device delivers photons of radiation. In an ever more precise fashion, state-of-the-art technology has recently allowed for both modulation of the radiation beam and imaging for this treatment delivery. This has resulted in better patient outcome with far fewer side effects than were achieved even a decade ago. Recently, a push has begun for proton therapy, which may have clinical advantage in select indications, although significant limitations for these devices have become apparent. In addition, currently, heavy particle therapy has been touted as a potential means to improve cancer patient outcomes. This article will highlight current benefits and drawbacks to modern radiation therapy and speculate on future tools that will likely dramatically improve radiation oncology.

Impaired natural killer cell self-education and "missing-self" responses in Ly49-deficient mice.

Ly49-mediated recognition of MHC-I molecules on host cells is considered vital for natural killer (NK)-cell regulation and education; however, gene-deficient animal models are lacking because of the difficulty in deleting this large multigene family. Here, we describe NK gene complex knockdown (NKC(KD)) mice that lack expression of Ly49 and related MHC-I receptors on most NK cells. NKC(KD) NK cells exhibit defective killing of MHC-I-deficient, but otherwise normal, target cells, resulting in defective rejection by NKC(KD) mice of transplants from various types of MHC-I-deficient mice. Self-MHC-I immunosurveillance by NK cells in NKC(KD) mice can be rescued by self-MHC-I-specific Ly49 transgenes. Although NKC(KD) mice display defective recognition of MHC-I-deficient tumor cells, resulting in decreased in vivo tumor cell clearance, NKG2D- or antibody-dependent cell-mediated cytotoxicity-induced tumor cell cytotoxicity and cytokine production induced by activation receptors was efficient in Ly49-deficient NK cells, suggesting MHC-I education of NK cells is a single facet regulating their total potential. These results provide direct genetic evidence that Ly49 expression is necessary for NK-cell education to self-MHC-I molecules and that the absence of these receptors leads to loss of MHC-I-dependent "missing-self" immunosurveillance by NK cells.

Tumorigenic adenovirus 12 cells evade NK cell lysis by reducing the expression of NKG2D ligands.

Activation of natural killer (NK) cells depends on a balance between signals received from activation and inhibitory ligands expressed on the surface of target cells. Tumorigenic human adenovirus 12 (Ad12) transformed cells express low levels of the NK cell inhibitory ligand MHC I, but do not exhibit increased sensitivity to NK cell lysis compared to their non-tumorigenic counterparts. Analysis of the expression of activation ligands that bind to the NKG2D receptor revealed that RAE1ß and H60 were reduced on the surface of Ad12 mouse cells as well as at the level of transcription. In accord with these results, RAE1 localization to the synapse and sensitivity to NK cell cytotoxicity were also diminished. The reduced transcription of the rat NKG2D ligands, RAEt1L and RRTL, in tumorigenic rat cells compared to non-tumorigenic counterparts implies that both mouse and rat cell lines share a common mechanism of NKG2D ligand activation subverted by Ad12.

Effect of Ly49 haplotype variance on NK cell function and education.

The class I MHC-specific receptors expressed by murine NK cells exhibit remarkable variation. Specific activating killer Ig-related receptor/Ly49 have major effects on autoimmune and infectious disease induction and outcome in humans and mice. However, these studies are greatly affected by individual background genetics. Furthermore, the educational impact of variable inhibitory KIR/Ly49 gene numbers on NK cell development and the subsequent ability to survey for MHC class I (MHC-I) expression remain unknown. To address these questions, Ly49 congenic mice were generated that maintain a 129-derived Ly49 gene cluster on a C57BL/6 genetic background (B6.Ly49(129) mice), and the in vitro and in vivo NK cell function of these mice was compared with their inbred parental 129S1 and C57BL/6 counterparts. Notably, target cell recognition directed by activating Ly49 receptors was profoundly affected by allelic variation in B6.Ly49(129) congenic cells versus C57BL/6 NK cells. Furthermore, when assessing NK cell function based on education and subsequent recognition of the C57BL/6 MHC-I haplotype by inhibitory Ly49 receptors, B6.Ly49(129) congenic mice exhibited robust NK cell activity, demonstrating efficient NK cell education by the 129S1 Ly49 cluster during development. The responsiveness of NK cells expressing 129S1 Ly49 was shown to be mediated by subsets expressing one or more self-MHC receptors, including Ly49I, Ly49O, Ly49V, and NKG2A. These findings demonstrate that the genetically segregating and diverse MHC-I and Ly49 loci in mice exhibit independent and epistatic effects on NK cell education that can be uncoupled during the intercrossing of inbred strains.