The mannose receptor influences antigen-presenting cells by direct interaction with CD45R0

The immune system has to manage the critical decision to induce either immunity or tolerance. Cells that take part in the regulatory processes of the immune system are amongst others antigen presenting cells (APCs), especially dendritic cells (DCs) and macrophages (M φΦs). Recently, it was shown that the mannose receptor (MR), known as an endocytic receptor expressed by specific APCs, is responsible for the induction of T cell tolerance. Under non-inflammatory conditions, the MR expressed by DCs can bind to CD45 on CD8+ T cells. The interaction of MR and CD45 induces the inhibition of CD45 phosphatase activity. Thereby, transcriptional T cell re-programming and up-regulation of CTLA-4 in T cells are initiated resulting in T cell tolerance. As CD45 is not only expressed by T cells but by all hematopoietic cells including APCs, the aim of this thesis was to investigate a putative influence of the MR on APCs by interaction with CD45. We could show that GM-CSF induced, bone marrow derived APCs (BM(GM-CSF) cells) express the lowest molecular isoform of CD45, CD45R0, that interacted with a recombinant MR construct comprising the CR, FN II, and CTLD1-2 domains of the MR (FcMR). This interaction impaired CD45 phosphatase activity in BM(GM-CSF) cells and altered intracellular signalling pathways. The capacity of APCs to stimulate antigen-specific T cells was altered by binding of FcMR to CD45. Antigen-specific T cells primed by FcMR pre-stimulated APCs showed reduced cytokine secretion of CD4+ T cells determined by IFN- γΓ levels and diminished cytotoxic activity of CD8+ T cells, although, proliferation of T cells remained unaffected. In addition, the application of supernatant containing soluble mannose receptor (sMR), that is shed by MR-positive cells, to stimulate BM(GM-CSF) cells also decreases CD45 phosphatase activity but in contrast supports an immunstimulatory phenotype of activated antigen-specific T cells. Recently, sMR was found to be highly elevated in several diseases. Here, we could show enhanced sMR serum levels after high-fat died or obesity in mice and human, respectively, pointing out a direct correlation of sMR expression and inflammatory metabolic processes

Current Concepts of Antigen Cross-Presentation

Dendritic cells have the ability to efficiently present internalized antigens on major histocompatibility complex (MHC) I molecules. This process is termed cross-presentation and is important role in the generation of an immune response against viruses and tumors, after vaccinations or in the induction of immune tolerance. The molecular mechanisms enabling cross-presentation have been topic of intense debate since many years. However, a clear view on these mechanisms remains difficult, partially due to important remaining questions, controversial results and discussions. Here, we give an overview of the current concepts of antigen cross-presentation and focus on a description of the major cross-presentation pathways, the role of retarded antigen degradation for efficient cross-presentation, the dislocation of antigens from endosomal compartment into the cytosol, the reverse transport of proteasome-derived peptides for loading on MHC I and the translocation of the cross-presentation machinery from the ER to endosomes. We try to highlight recent advances, discuss some of the controversial data and point out some of the major open questions in the field

Soluble mannose receptor induces proinflammatory macrophage activation and metaflammation

Proinflammatory activation of macrophages in metabolic tissues is critically important in the induction of obesity-induced metaflammation. Here, we demonstrate that the soluble mannose receptor (sMR) plays a direct functional role in both macrophage activation and metaflammation. We show that sMR binds CD45 on macrophages and inhibits its phosphatase activity, leading to an Src/Akt/ NF-kappa B-mediated cellular reprogramming toward an inflammatory phenotype both in vitro and in vivo. Remarkably, increased serum sMR levels were observed in obese mice and humans and directly correlated with body weight. Importantly, enhanced sMR levels increase serum proinflammatory cytokines, activate tissue macrophages, and promote insulin resistance. Altogether, our results reveal sMR as regulator of proinflammatory macrophage activation, which could constitute a therapeutic target for metaflammation and other hyperinflammatory diseases.Diabetes mellitus: pathophysiological changes and therap

Fast High Resolution Volume Carving for 3D Plant Shoot Reconstruction

Volume carving is a well established method for visual hull reconstruction and has been successfully applied in plant phenotyping, especially for 3d reconstruction of small plants and seeds. When imaging larger plants at still relatively high spatial resolution (≤1 mm), well known implementations become slow or have prohibitively large memory needs. Here we present and evaluate a computationally efficient algorithm for volume carving, allowing e.g., 3D reconstruction of plant shoots. It combines a well-known multi-grid representation called “Octree” with an efficient image region integration scheme called “Integral image.” Speedup with respect to less efficient octree implementations is about 2 orders of magnitude, due to the introduced refinement strategy “Mark and refine.” Speedup is about a factor 1.6 compared to a highly optimized GPU implementation using equidistant voxel grids, even without using any parallelization. We demonstrate the application of this method for trait derivation of banana and maize plants

phenoSeeder - A robot system for single-seed handling and measurement of seed traits

The quality of seeds is essential for plant breeding with very different variability of relevant traits for different crops. In DPPN we have developed a modular phenoSeeder system consisting of an industrial pick-and-place robot and different measurement stations. It enables precise and effi-cient seed handling with low error rates and collecting seed traits such as size or weight of dif-ferent plant species. The robot is equipped with different tools used for seed handling. Depend-ing on seed size, each tool uses a specifically designed needle to which vacuum or overpressure is supplied to suck or release individual seeds, respectively. The picking system has been success-fully tested for seeds of various species such as Arabidopsis thaliana, Brassica napus or Hordeum vulgare varying in size from 180 μm to 8 mm.The seed handling cycle starts at a so called seed source station. It consists of a circular glass pane on which the seeds are manually dispersed and which is uniformly illuminated by an LED ring from below. A color camera underneath the glass pane acquires images of the seeds. The images are analyzed to extract both seed positions and properties such as projected seed area, length and width. For the different seed types individual segmentation parameters have been determined. The position of a single seed is defined by its image coordinates describing the seed’s center of mass. A 2D-homography is used to map image coordinates to world coordinates which can be approached by the robot. After picking up a seed, it can be carried to measure-ment stations like a balance or a 3D-reconstruction station. Each single seed gets its own ID and all measured traits are transferred to a database allowing seed-to-plant tracking in phenotyping pipelines. The modular software concept makes it possible to simply add new measurement stations without having to change the existing software.After traits are measured, the seed is released either into a pot with soil or at a defined position of a well plate. Currently a sowing procedure without moving to a measurement station takes 2.9 to 3.3 seconds depending on the pot’s distance to the seed source station. In case that a seed could not be released, the robot moves to a needle cleaner station where two rotating brushes clean the needle. Another part within DPPN is the construction of a quickSeeder system, based on a similar robot as that of the phenoSeeder. It will enable fast planting of seeds of which the respective traits were scored and which were placed in well plates by the phenoSeeder sys-tem beforehand

Intraendosomal flow cytometry: A novel approach to analyze the protein composition of antigen-loaded endosomes

Tumorimmunolog