Many bacteria-associated polysaccharides induce long-lived antibody responses that protect against pathogenic microorganisms. The maintenance of polysaccharide-specific antibody titers may be due to long-lived plasma cells or ongoing antigen-driven B cell activation due to polysaccharide persistence. BALB/c and VHJ558.3 transgenic (TG) mice respond to α 1→3-dextran (DEX) by generating a peak anti-DEX response at 7 days, followed by maintenance of serum antibody levels for up to 150 days. Analysis of the cellular response to DEX identified a population of short-lived, cyclophosphamide sensitive DEX-specific plasmablasts in the spleen, and a quiescent, cyclophosphamide resistant DEX-specific antibody-secreting population in the bone marrow. BrdU pulse-chase experiments demonstrated the longevity of the DEX-specific antibody-secreting population in the bone marrow. Splenic DEX-specific plasmablasts were located in the red pulp with persisting DEX-associated CD11c+ dendritic cells 90 days after immunization, whereas DEX was not detected in the bone marrow after 28 days. Selective depletion of short-lived DEX-specific plasmablasts and memory B1b B cells using cyclophosphamide and anti-CD20 treatment had a minimal impact on the maintenance of serum anti-DEX antibodies. Collectively, these findings demonstrate that the maintenance of serum polysaccharide-specific antibodies is the result of continuous antigen-driven formation of short-lived plasmablasts in the spleen and a quiescent population of antibody-secreting cells maintained in the bone marrow for a long duration.
Germline DH sequences are required for the generation of natural antibodies reactive to bacterial phosphorylcholine but not for those reactive to self-antigen.
Autoantibodies can be present years to decades prior to the onset of disease manifestations in autoimmunity. This suggests that the initial autoimmune trigger involves a peripheral lymphoid component, which ultimately drives disease pathology in local tissues later in life. Here we show Sjögren’s Syndrome manifestations that develop in aged NOD.H-2h4 mice were driven by and dependent on peripheral dysregulation that arose in early life. Specifically, elimination of spontaneous germinal centers in spleens of young NOD.H-2h4 mice by transient blockade of CD40 ligand (CD40L) or splenectomy abolished Sjögren’s pathology of aged mice. Strikingly, a single injection of anti-CD40L at 4 weeks-of-age prevented tertiary follicle neogenesis and greatly blunted the formation of key autoantibodies implicated in glandular pathology, including anti-muscarinic receptor antibodies. Microarray profiling of the salivary gland characterized the expression pattern of genes that increased with disease progression and showed early anti-CD40L greatly repressed B cell function, while having a broader effect on multiple biological pathways including IL-12 and interferon signaling. Importantly, a single, prophylactic treatment with anti-CD40L also inhibited the development of autoimmune thyroiditis and diabetes in NOD.H-2h4 and NOD mice, respectively, supporting a key role for CD40L in the pathophysiology of several autoimmune models. These results strongly suggest early peripheral immune dysregulation gives rise to autoimmune manifestations later in life and for diseases pre-dated by autoantibodies, early prophylactic intervention with biologics may prove efficacious.
Ectopic follicles are non-encapsulated organized lymphoid structures that form at sites of inflammation and presumably contribute to the activation and differentiation of cells with autoreactive potential within target tissues. As such, directed targeting of ectopic follicles in settings of autoimmunity may provide a means to specifically inhibit the activation of autoreactive cells without impairing protective immune responses ongoing in peripheral lymphoid tissues. NOD·H2h4 mice are a non-diabetic strain of NOD mice which develop a Sjögren's syndrome-like disease which includes the formation of ectopic follicles in the salivary gland and characteristic Sjögren's autoantibodies. The goal of these studies was to better characterize the formation of ectopic follicles in this model and to explore their contribution to autoimmunity. Our studies show that by 8 weeks of age, young NOD·H2h4 mice spontaneously develop an abundance of splenic germinal centers, prior to the emergence of lymphocyte infiltration in the salivary gland tissue. Ectopic follicle formation in the salivary gland begins to appear in these mice between 12 and 16 weeks of age. Interestingly, anti-Ro and anti-La autoantibodies precede the development of ectopic follicles in young NOD·H2h4 mice. In contrast, production of anti-dsDNA antibodies is delayed and largely coincides with the formation of ectopic follicles in these mice. These data suggest that tertiary lymphoid structures may arise from the trafficking of activated T and B cells to sites of inflammation in non-lymphoid tissues. Furthermore, local presentation of autoantigens may then promote the expansion of autoreactive cells with specificities distinct from those generated in the splenic micro-environment.
The present investigation studies the processing of A356 Al-Si alloy containing up to 5% vol.-% nano-sized al2o3 particles having size less than 500 nm. Composites were prepared using semi-solid casting route. To evaluate the results the alloys were further characterised by various metallurgical and mechanical characterization methods. The results showed that introducing nano-particles into semi-solid slurries promises to be a successful route for producing a new generation of cast metal matrix nano-composites (MMNCs). The nano-composites showed high strength values associated with superior ductility, low porosity content, high corrosion resistance, and improved electrical conductivity compared to the alloy without particles addition under the same casting conditions.
The effect of the friction stir welding (FSW) parameters on the microstructure and mechanical characteristics of A319 cast Al alloy has been investigated. Plates from the investigated alloy were welded together under different tool rotational (v) and welding (u) speeds. The results showed the possibility of welding and obtaining sound joints from A319 cast Al alloy using FSW. The welded zones exhibited many advantages over the base material (BM) such as, lower porosity content, extra fine non-dendritic a-Al grains, and extra fine more homogeneously dispersed Si particles. The size of both a-Al grains and Si particles was found to be increase by increasing both tool rotational and welding speeds. The welded joints showed better mechanical properties than the BM. It has been found that increasing the tool rotational speed and/or the welding speed reduces both the tensile and yield strengths of the welded joints, however, they still higher than of the BM. In contrast, increasing the aforementioned speeds tends to increase the ductility of the welded joints.
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