Dr. Jekyll and Mr. Hyde - Distinctiveness and plasticity of mononuclear phagocytes in the mouse skin

Antigen-presenting cells are crucial participants in the defense of the body against potentially pathogenic invaders. In an immature state, they reside in all peripheral sites, where they can recognize and take up antigens. Once they have encountered antigens, they may become activated. As a consequence, they will migrate to draining lymph nodes, where they can activate naïve T cells to become the main effector cells of the immune system. These T cells can then migrate back to the affected site to help to rid the body of the invaders. The skin, as the largest organ of the body, contains many cells that have the potential to develop into effective antigen-presenting cells (discussed in Chapters 1 and 2). The epidermis, the outermost layer, has its population of Langerhans cells. These cells form a tight network with connecting cellular protrusions. Via these, they sample endogenous as well as exogenous molecules that get into contact with the epidermis. As these cells have been known now for quite a while, their functions in the epidemis as well as after migration into skin-draining lymph nodes have been extensively studied. The dermis, the second layer of the skin, also contains cells with potential antigenpresenting capacity. These cells are, in contrast to the epidermal Langerhans cells, much less well investigated. The aim of this thesis study, outlined in Chapter 3, therefore was to analyze the antigen-presenting cells of the mouse dermis in more detail and to compare them to the epidermis-derived Langerhans cells

Dendritic cells in vivo and in vitro

Dendritic cells (DC) are crucial cells of the immune system, and bridge the essential connection between innate and adaptive immunity. They reside in the periphery as sentinels where they take up antigens. Upon activation, they migrate to lymphoid organs and present there the processed antigens to T cells, thereby activating them and eliciting a potent immune response. Dendritic cells are bone marrow-derived cells, still big controversies exist about their in vivo development. In vitro, DC can be generated from multiple precursor cells, among them lymphoid and myeloid committed progenitors. Although it remains unknown how DC are generated in vivo, studying the functions of in vitro generated DC results in fundamental knowledge of the DC biology with promising applications for future medicine. Therefore, in this review, we present current protocols for the generation of DC from precursors in vitro. We will do this for the mouse system, where most research occurs and for the human system, where research concentrates on implementing DC biology in disease treatments

The CMS Phase-1 pixel detector upgrade

The CMS detector at the CERN LHC features a silicon pixel detector as its innermost subdetector. The original CMS pixel detector has been replaced with an upgraded pixel system (CMS Phase-1 pixel detector) in the extended year-end technical stop of the LHC in 2016/2017. The upgraded CMS pixel detector is designed to cope with the higher instantaneous luminosities that have been achieved by the LHC after the upgrades to the accelerator during the first long shutdown in 2013–2014. Compared to the original pixel detector, the upgraded detector has a better tracking performance and lower mass with four barrel layers and three endcap disks on each side to provide hit coverage up to an absolute value of pseudorapidity of 2.5. This paper describes the design and construction of the CMS Phase-1 pixel detector as well as its performance from commissioning to early operation in collision data-taking.Peer reviewe

Dermal mononuclear phagocytes

In immune responses of the skin, the connectivetissue environment of the dermis plays a decisive role.Large numbers of resident mononuclear phagocytesare located here and these are thought to be crucialfor the initiation and regulation of such responses.Surprisingly, the characterization of dermalmononuclear phagocytes, often distinguished asmacrophages and dendritic cells (DC), has beenlimited compared to those in other immune organsand to their Langerhans cell counterparts in theepidermis. This is likely explained by the difficulty toobtain dermal cells in large quantity. In this chapter,we will provide an overview of the current insights ondermal mononuclear phagocytes, using the differenttechnical approaches to study these cells as a guideline. For practical purposeswe will focus primarily on the steady-state situation and discuss this for humanand mouse skin. In situ analysis using skin sections has indicated thatmononuclear phagocytes represent a remarkably large proportion of nucleatedcells in the dermis, comprising multiple, phenotypically distinct subsets. Usingskin explant cultures or freshly isolated cells from dermal tissue, single cells canbe obtained. These approaches confirm the extensive heterogeneity of the dermalmononuclear phagocytes. Interpreting the available data, we propose that adevelopmental relationship may exist between the major subsets. While the cellsmigrate upwards from the deeper layers in the dermis they mature and changefrom endocytic macrophage-like cells to cells with an immunostimulatory DCphenotype, which may leave the dermis via afferent lymphatics to interact withthe immune system in skin-draining lymph nodes

Dermal mononuclear phagocytes

In immune responses of the skin, the connectivetissue environment of the dermis plays a decisive role.Large numbers of resident mononuclear phagocytesare located here and these are thought to be crucialfor the initiation and regulation of such responses.Surprisingly, the characterization of dermalmononuclear phagocytes, often distinguished asmacrophages and dendritic cells (DC), has beenlimited compared to those in other immune organsand to their Langerhans cell counterparts in theepidermis. This is likely explained by the difficulty toobtain dermal cells in large quantity. In this chapter,we will provide an overview of the current insights ondermal mononuclear phagocytes, using the differenttechnical approaches to study these cells as a guideline. For practical purposeswe will focus primarily on the steady-state situation and discuss this for humanand mouse skin. In situ analysis using skin sections has indicated thatmononuclear phagocytes represent a remarkably large proportion of nucleatedcells in the dermis, comprising multiple, phenotypically distinct subsets. Usingskin explant cultures or freshly isolated cells from dermal tissue, single cells canbe obtained. These approaches confirm the extensive heterogeneity of the dermalmononuclear phagocytes. Interpreting the available data, we propose that adevelopmental relationship may exist between the major subsets. While the cellsmigrate upwards from the deeper layers in the dermis they mature and changefrom endocytic macrophage-like cells to cells with an immunostimulatory DCphenotype, which may leave the dermis via afferent lymphatics to interact withthe immune system in skin-draining lymph nodes

Dermal mononuclear phagocytes

In immune responses of the skin, the connective tissue environment of the dermis plays a decisive role. Large numbers of resident mononuclear phagocytes are located here and these are thought to be crucial for the initiation and regulation of such responses. Surprisingly, the characterization of dermal mononuclear phagocytes, often distinguished as macrophages and dendritic cells (DC), has been limited compared to those in other immune organs and to their Langerhans cell counterparts in the epidermis. This is likely explained by the difficulty to obtain dermal cells in large quantity. In this chapter, we will provide an overview of the current insights on dermal mononuclear phagocytes, using the different technical approaches to study these cells as a guideline. For practical purposes we will focus primarily on the steady-state situation and discuss this for human and mouse skin. In situ analysis using skin sections has indicated that mononuclear phagocytes represent a remarkably large proportion of nucleated cells in the dermis, comprising multiple, phenotypically distinct subsets. Using skin explant cultures or freshly isolated cells from dermal tissue, single cells can be obtained. These approaches confirm the extensive heterogeneity of the dermal mononuclear phagocytes. Interpreting the available data, we propose that a developmental relationship may exist between the major subsets. While the cells migrate upwards from the deeper layers in the dermis they mature and change from endocytic macrophage-like cells to cells with an immunostimulatory DC phenotype, which may leave the dermis via afferent lymphatics to interact with the immune system in skin-draining lymph nodes

UBA1 and UBA2, Two Proteins That Interact with UBP1, a Multifunctional Effector of Pre-mRNA Maturation in Plants

Nicotiana plumbaginifolia UBP1 is an hnRNP-like protein associated with the poly(A)(+) RNA in the cell nucleus. Consistent with a role in pre-mRNA processing, overexpression of UBP1 in N. plumabaginifolia protoplasts enhances the splicing of suboptimal introns and increases the steady-state levels of reporter mRNAs, even intronless ones. The latter effect of UBP1 is promoter specific and appears to be due to UBP1 binding to the 3′ untranslated region (3′-UTR) and protecting the mRNA from exonucleolytic degradation (M. H. L. Lambermon, G. G. Simpson, D. A. Kirk, M. Hemmings-Mieszczak, U. Klahre, and W. Filipowicz, EMBO J. 19:1638-1649, 2000). To gain more insight into UBP1 function in pre-mRNA maturation, we characterized proteins interacting with N. plumbaginifolia UBP1 and one of its Arabidopsis thaliana counterparts, AtUBP1b, by using yeast two-hybrid screens and in vitro pull-down assays. Two proteins, UBP1-associated proteins 1a and 2a (UBA1a and UBA2a, respectively), were identified in A. thaliana. They are members of two novel families of plant-specific proteins containing RNA recognition motif-type RNA-binding domains. UBA1a and UBA2a are nuclear proteins, and their recombinant forms bind RNA with a specificity for oligouridylates in vitro. As with UBP1, transient overexpression of UBA1a in protoplasts increases the steady-state levels of reporter mRNAs in a promoter-dependent manner. Similarly, overexpression of UBA2a increases the levels of reporter mRNAs, but this effect is promoter independent. Unlike UBP1, neither UBA1a nor UBA2a stimulates pre-mRNA splicing. These and other data suggest that UBP1, UBA1a, and UBA2a may act as components of a complex recognizing U-rich sequences in plant 3′-UTRs and contributing to the stabilization of mRNAs in the nucleus