GM-CSF-Producing Th Cells in Rats Sensitive and Resistant to Experimental Autoimmune Encephalomyelitis

Given that granulocyte macrophage colony-stimulating factor (GM-CSF) is identified as the key factor to endow auto-reactive Th cells with the potential to induce neuroinflammation in experimental autoimmune encephalomyelitis (EAE) models, the frequency and phenotype of GM-CSF-producing (GM-CSF+) Th cells in draining lymph nodes (dLNs) and spinal cord (SC) of Albino Oxford (AO) and Dark Agouti (DA) rats immunized for EAE were examined. The generation of neuroantigen-specific GM-CSF+ Th lymphocytes was impaired in dLNs of AO rats (relatively resistant to EAE induction) compared with their DA counterparts (susceptible to EAE) reflecting impaired CD4+ lymphocyte proliferation and less supportive of GM-CSF+ Th cell differentiation dLN cytokine microenvironment. Immunophenotyping of GM-CSF+ Th cells showed their phenotypic heterogeneity in both strains and revealed lower frequency of IL-17+ IFN-gamma+, IL-17+ IFN-gamma-, and IL-17-IFN-gamma+ cells accompanied by higher frequency of IL-17-IFN-gamma- cells among them in AO than in DA rats. Compared with DA, in AO rats was also found (i) slightly lower surface density of CCR2 (drives accumulation of highly pathogenic GM-CSF+ IFN-gamma+ Th17 cells in SC) on GM-CSF+ IFN-gamma+ Th17 lymphocytes from dLNs, and (ii) diminished CCL2 mRNA expression in SC tissue, suggesting their impaired migration into the SC. Moreover, dLN and SC cytokine environments in AO rats were shown to be less supportive of GM-CSF+ IFN-gamma+ Th17 cell differentiation (judging by lower expression of mRNAs for IL-1 beta, IL-6 and IL-23/p19). In accordance with the (i) lower frequency of GM-CSF+ Th cells in dLNs and SC of AO rats and their lower GM-CSF production, and (ii) impaired CCL2 expression in the SC tissue, the proportion of proinflammatory monocytes among peripheral blood cells and their progeny (CD45(hi) cells) among the SC CD11b+ cells were reduced in AO compared with DA rats. Collectively, the results indicate that the strain specificities in efficacy of several mechanisms controlling (auto) reactive CD4+ lymphocyte expansion/differentiation into the cells with pathogenic phenotype and migration of the latter to the SC contribute to AO rat resistance to EAE

Synovial CD4+ T-cell-derived GM-CSF supports the differentiation of an inflammatory dendritic cell population in rheumatoid arthritis

OBJECTIVE: A population of synovial inflammatory dendritic cells (infDCs) has recently been identified in rheumatoid arthritis (RA) and is thought to be monocyte-derived. Here, we investigated the role and source of granulocyte macrophage-colony-stimulating factor (GM-CSF) in the differentiation of synovial infDC in RA. METHODS: Production of GM-CSF by peripheral blood (PB) and synovial fluid (SF) CD4+ T cells was assessed by ELISA and flow cytometry. In vitro CD4+ T-cell polarisation experiments were performed with T-cell activating CD2/CD3/CD28-coated beads in the absence or presence of pro-Th1 or pro-Th17 cytokines. CD1c+ DC and CD16+ macrophage subsets were flow-sorted and analysed morphologically and functionally (T-cell stimulatory/polarising capacity). RESULTS: RA-SF CD4+ T cells produced abundant GM-CSF upon stimulation and significantly more than RA-SF mononuclear cells depleted of CD4+ T cells. GM-CSF-producing T cells were significantly increased in RA-SF compared with non-RA inflammatory arthritis SF, active RA PB and healthy donor PB. GM-CSF-producing CD4+ T cells were expanded by Th1-promoting but not Th17-promoting conditions. Following coculture with RA-SF CD4+ T cells, but not healthy donor PB CD4+ T cells, a subpopulation of monocytes differentiated into CD1c+ infDC; a process dependent on GM-CSF. These infDC displayed potent alloproliferative capacity and enhanced GM-CSF, interleukin-17 and interferon-γ production by CD4+ T cells. InfDC with an identical phenotype to in vitro generated cells were significantly enriched in RA-SF compared with non-RA-SF/tissue/PB. CONCLUSIONS: We demonstrate a therapeutically tractable feedback loop of GM-CSF secreted by RA synovial CD4+ T cells promoting the differentiation of infDC with potent capacity to induce GM-CSF-producing CD4+ T cells

The new materials science diffractometer STRESS SPEC at FRM II

In response to the development of new materials and the application of materials and components in new technologies the direct measurement, calculation and evaluation of textures and residual stresses has gained worldwide significance in recent years. Non destructive analysis for phase specific residual stresses and textures is only possible by means of diffraction methods. In order to cater for the development of these analytical techniques the new Materials Science Diffractometer STRESS SPEC at FRM II is designed to be equally applied to texture and residual stress analyses by virtue of its flexible configuration. The system compromises a highly flexible monochromator setup using three different monochromators Ge 511 , bent silicon 400 and pyrolitic graphite PG . This range of monochromators and the possibility to vary the take off angles from 2 amp; 952;M 35 to 110 allows wavelength adjustment such that measurements can be performed around a scattering angle of 2 amp; 952;S 90 . This is important in order to optimise neutron flux and resolution, especially for stress analysis on components, since the gauge volume element in that case is cubic and large vertical divergences due to focusing monochromators do not affect the spatial resolution. The instrument is now available for routine operation and here we will present details of recent experiments and instrument performanc

On the Fatigue Behavior and Associated Effect of Residual Stresses in

Mechanical surface treatments, such as deep rolling, shot peening and laser shock peening, can significantly improve the fatigue behavior of highly stressed metallic components. Deep rolling is an especially attractive technique since it is possible to generate deep, near-surface compressive residual stresses and work hardening while retaining a relatively smooth surface finish. Indeed, this technique is best known for increasing the fatigue strength and lifetime of steel components such as crankshafts. Although most work on deep rolling has been on steels, recently it has also been applied with reasonable success to titanium alloys. Accordingly, in this investigation, we examine the effect of deep rolling on the high-cycle fatigue behavior of Ti-6Al-4V, with particular emphasis on the thermal and mechanical stability of the residual stress states and near-surface microstructures. Preliminary results on laser shock peened Ti-6Al-4V are also presented for comparison. In addition, we examine whether these surface treatments are effective in retaining fatigue strength at the higher temperatures of 300 to 450#C. Based on the cyclic deformation and stress/life behavior, together with the X-ray and microstructural observations, it is found that deep rolling can be quite effective in retarding the initiation and initial propagation of fatigue cracks in Ti-6Al-4V at such higher temperatures, despite the almost complete relaxation of the residual stresses at the surface. This clearly implies that, in addition to residual stresses, near-surface microstructures, which in Ti-6Al-4V consist of ultrafine near-surface nanostructures, play a critical role in the enhancement of fatigue lifetimes by mechanical surface treatments

In-Situ Observations of Low-Cycle Fatigue Damage in Cast AM60B Magnesium in an Environmental Scanning Electron Microscope

We present in-situ observations of low-cycle fatigue damage in cast AM60B magnesium. The in-situ fatigue tests were conducted in an environmental scanning electron microscope under both high vacuum and 20 Torr of water vapor. In both environments, fatigue cracks were observed to form and grow within the dendrite cells and through the interdendritic regions. Crack formation and growth through the dendrite cells proceeded along persistent slip bands. The persistent slip bands were typically oriented at about 45 deg with respect to the loading axis and were more frequently observed in relatively large dendrite cells. Crack formation and growth through the Mg interdendritic regions, laden with Al-Mg intermetallic particles, was facilitated by slip incompatibilities in adjacent dendrite cells, microporosity, and damaged second-phase particles. The detectable “crack-formation” size at slip bands and within interdendritic regions was typically equivalent to the dendrite cell size (DCS), since cracks rapidly spanned this distance once nucleated. Cracks formed during cycling in vacuum were more uniformly distributed and showed a lack of complete closure upon unloading, in contrast to cracks formed during cycling in water vapor. The cracks formed in water vapor were much more isolated and showed indication of significant environmental attack and associated embrittlement at the crack tip, as evidenced by the near-perfect mating of crack faces upon unloading. Final fracture occurred by the coalescence of numerous cracks throughout the microstructure, distributed differently depending on the testing environment. The water-vapor environment accelerated the formation of selected, isolated cracks, leading to more localized damage compared to the highly distributed damage growth and coalescence observed in the material cycled in vacuum