UTLS water vapour from SCIAMACHY limb measurementsV3.01 (2002-2012).

The SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) aboard the Envisat satellite provided measurements from August 2002 until April 2012. SCIAMACHY measured the scattered or direct sunlight using different observation geometries. The limb viewing geometry allows the retrieval of water vapour at about 10-25 km height from the near-infrared spectral range (1353-1410 nm). These data cover the upper troposphere and lower stratosphere (UTLS), a region in the atmosphere which is of special interest for a variety of dynamical and chemical processes as well as for the radiative forcing. Here, the latest data version of water vapour (V3.01) from SCIAMACHY limb measurements is presented and validated by comparisons with data sets from other satellite and in situ measurements. Considering retrieval tests and the results of these comparisons, the V3.01 data are reliable from about 11 to 23 km and the best results are found in the middle of the profiles between about 14 and 20 km. Above 20 km in the extra tropics V3.01 is drier than all other data sets. Additionally, for altitudes above about 19 km, the vertical resolution of the retrieved profile is not sufficient to resolve signals with a short vertical structure like the tape recorder. Below 14 km, SCIAMACHY water vapour V3.01 is wetter than most collocated data sets, but the high variability of water vapour in the troposphere complicates the comparison. For 14-20 km height, the expected errors from the retrieval and simulations and the mean differences to collocated data sets are usually smaller than 10 % when the resolution of the SCIAMACHY data is taken into account. In general, the temporal changes agree well with collocated data sets except for the Northern Hemisphere extratropical stratosphere, where larger differences are observed. This indicates a possible drift in V3.01 most probably caused by the incomplete treatment of volcanic aerosols in the retrieval. In all other regions a good temporal stability is shown. In the tropical stratosphere an increase in water vapour is found between 2002 and 2012, which is in agreement with other satellite data sets for overlapping time periods.

Metalloproteinase-dependent control of thymocyte differentiation and proliferation.

The development of T cells in the thymus is dependent on interactions between thymocytes and thymic stromal cells, on stimulation by growth factors, and on the binding to and migration along extracellular matrix (ECM) components. As metalloproteinases (MP) are involved in processes such as growth factor release and ECM modelling, we assessed the effect of MP inhibitors on T-cell development using fetal thymic organ culture systems. MP inhibitors significantly reduced the numbers of CD4/CD8 double-positive (DP) and mature single-positive thymocytes generated, correlated with a reduced number of cell cycles between the double-negative (DN)3 and DP stages. The progression of early thymocyte progenitors through the DN1-4 stages of development was also severely affected, including incomplete upregulation of CD25, decreased DN3 cell numbers, reduced rearrangement of the T-cell receptor (TCR)-beta locus and expression of intracellular TCR-beta by fewer DN3 cells. When purified DN1 cells were utilized as donor cells in reaggregate thymic organ cultures, essentially no DP thymocytes were produced in the presence of MP inhibitors. The results suggest that MP inhibitors affect the differentiation of developing thymocytes before, and reduce proliferation after, pre-TCR-mediated selection.

Immature thymocytes that fail to express TCRbeta and/or TCRgamma delta proteins die by apoptotic cell death in the CD44(-)CD25(-) (DN4) subset.

Pre-TCR/CD3 signals are essential for survival and maturation of (CD44(-)25(+)) DN3 thymocytes via the (CD44(-)25(-)) DN4 stage to CD4(+)CD8(+) (DP) cells, a process termed beta-selection. The exact developmental stages of apoptosis resulting from lack of pre-TCR/CD3 signals have so far not been determined. Here we analyzed apoptotic cell death in relation to expression of clonotypic TCR polypeptides and to cell cycle status in immature thymocyte subpopulations of wild type (wt) mice and of several strains of mice with compromised pre-TCR/CD3 signaling complexes. In wt mice or pre-TCR/CD3-deficient mice, apoptotic cells could not be detected among DN3 cells but accumulated in a subset of DN4 expressing CD69. Apoptotic CD69(+)DN4 cells were rare in wt mice and were found among DN4 cells that were negative or low for intracellular TCRbeta and negative for TCRgamma delta polypeptide chains. Apoptotic CD69(+)DN4 cells were abundant in pre-TCR/CD3 signaling-deficient mice in which most DN4 cells failed to express clonotypic TCR polypeptides. Survival of DN4 cells, but not maturation of DN3 cells to DN4, was found to depend on the expression of clonotypic TCR polypeptides in the same cell. The results suggest that thymocytes unsuccessful in alpha beta or in gamma delta lineage development die by apoptosis in the DN4 subset.

Developmentally regulated expression of the transmembrane adaptor protein trim in fetal and adult T cells.

TRIM is a recently identified transmembrane adaptor protein which is exclusively expressed in T cells and natural killer (NK) cells. In peripheral blood T cells TRIM has been reported to coprecipitate, comodulate, and cocap with the T-cell receptor (TCR), suggesting that it is an integral component of the TCR/CD3/zeta complex. Here we investigate the expression of TRIM mRNAs and proteins in developing thymocytes. Two splicing isoforms with open reading frames are observed, namely a full length (TRIM) and a truncated version (DeltaTM-TRIM). The latter lacks the extracellular and transmembrane domains as well as the first 10 cytoplasmic aminoacids and is significantly expressed only as mRNA in early fetal thymocytes. TRIM mRNA is detected in all mainstream thymocyte subsets in adult mice. TRIM protein, in contrast, first appears in the DN2 (CD44+ CD25+) subset of adult double negative (DN) cells. In fetal thymocyte development, TRIM mRNA is seen from dg 14.5 onwards whereas TRIM protein appears first on dg 16.5. In contrast to the adult, the TRIM protein was seen in a subset of fetal DN1 cells. In fetal and adult thymocytes, TRIM protein expression was highest in DN2, DN3 (CD44-25+) and in DP cells, compatible with a functional role at or around phases of thymic selection.

Expression and selection of productively rearranged TCR beta VDJ genes are sequentially regulated by CD3 signaling in the development of NK1.1(+) alpha beta T cells.

The generation of thymic NK1.1(+)alpha beta T (NKT) cells involves positive selection of cells enriched for V(alpha)14/V(beta)8 TCR by CD1d MHC class I molecules. However, it has not been determined whether positive selection is preceded by pre-TCR-dependent beta selection. Here we studied NKT cell development in CD3 signaling-deficient mice (CD3 zeta/eta(-/-) and/or p56(lck-/-)) and TCR alpha-deficient mice. In contrast to wild-type mice, NK1.1(+) thymocytes in CD3 signaling-deficient mice are approximately 10-fold reduced in number, do not exhibit V(alpha)14-J(alpha)281 rearrangements and fail to express alpha beta TCR at the cell surface. However, they exhibit TCR beta VDJ rearrangements and pre-T alpha mRNA, suggesting that they contain pre-NKT cells. Strikingly, pre-NKT cells of CD3 zeta/Lck double-deficient mice fail to express TCR beta mRNA and protein. Whereas in wild-type NKT cells TCR beta VDJ junctions are selected for productive V(beta)8 and against productive V(beta)5 rearrangements, V(beta)8 and V(beta)5 rearrangements are non-selected in pre-NKT cells of CD3 signaling-deficient mice. Thus, pre-NKT cell development in CD3 signaling-deficient mice is blocked after rearrangement of TCR beta VDJ genes but before expression of TCR beta proteins. Most NKT cells of TCR alpha-deficient mice exhibit cell surface gamma delta TCR. In contrast to pre-NKT cells of CD3 signaling-deficient mice, approximately 25% of NKT cells of TCR alpha-deficient mice exhibit intracellular TCR beta polypeptide chains. Moreover, both V(beta)8 and V(beta)5 families are selected for in-frame VDJ joints in the TCR beta(+) NKT cell subset of TCR alpha-deficient mice. The data suggest that CD3 signals regulate initial TCR beta VDJ gene expression prior to beta selection in developing pre-NKT cells.

The duration of nuclear residence of NFAT determines the pattern of cytokine expression in human SCID T cells.

The expression of cytokine genes and other inducible genes is crucially dependent on the pattern and duration of signal transduction events that activate transcription factor binding to DNA. Two infant patients with SCID and a severe defect in T cell activation displayed an aberrant regulation of the transcription factor NFAT. Whereas the expression levels of the NFAT family members NFAT1, -2, and -4 were normal in the patients' T cells, dephosphorylation and nuclear translocation of these NFAT proteins occurred very transiently and incompletely upon stimulation. Only after inhibition of nuclear export with leptomycin B were we able to demonstrate a modest degree of nuclear translocation in the patients' T cells. This transient activation of NFAT was not sufficient to induce the expression of several cytokines, including IL-2, IL-3, IL-4, and IFN-gamma, whereas mRNA levels for macrophage inflammatory protein-1alpha, GM-CSF, and IL-13 were only moderately reduced. By limiting the time of NFAT activation in normal control cells using the calcineurin inhibitor cyclosporin A, we were able to mimic the cytokine expression pattern in SCID T cells, suggesting that the expression of different cytokine genes is differentially regulated by the duration of NFAT residence in the nucleus.

Cytotoxic T lymphocyte epitopes of HIV-1 Nef: Generation of multiple definitive major histocompatibility complex class I ligands by proteasomes.

Although a pivotal role of proteasomes in the proteolytic generation of epitopes for major histocompatibility complex (MHC) class I presentation is undisputed, their precise function is currently the subject of an active debate: do proteasomes generate many epitopes in definitive form, or do they merely generate the COOH termini, whereas the definitive NH(2) termini are cleaved by aminopeptidases? We determined five naturally processed MHC class I ligands derived from HIV-1 Nef. Unexpectedly, the five ligands correspond to only three cytotoxic T lymphocyte (CTL) epitopes, two of which occur in two COOH-terminal length variants. Parallel analyses of proteasomal digests of a Nef fragment encompassing the epitopes revealed that all five ligands are direct products of proteasomes. Moreover, in four of the five ligands, the NH(2) termini correspond to major proteasome cleavage sites, and putative NH(2)-terminally extended precursor fragments were detected for only one of the five ligands. All ligands are transported by the transporter associated with antigen processing (TAP). The combined results from these five ligands provide strong evidence that many definitive MHC class I ligands are precisely cleaved at both ends by proteasomes. Additional evidence supporting this conclusion is discussed, along with contrasting results of others who propose a strong role for NH(2)-terminal trimming with direct proteasomal epitope generation being a rare event.

Th1/Th2-regulated expression of arginase isoforms in murine macrophages and dendritic cells.

Activated murine macrophages metabolize arginine by two alternative pathways involving the enzymes inducible NO synthase (iNOS) or arginase. The balance between the two enzymes is competitively regulated by Th1 and Th2 T helper cells via their secreted cytokines: Th1 cells induce iNOS, whereas Th2 cells induce arginase. Whereas the role of macrophages expressing iNOS as inflammatory cells is well established, the functional competence of macrophages expressing arginase remains a matter of speculation. Two isoforms of mammalian arginases exist, hepatic arginase I and extrahepatic arginase II. We investigated the regulation of arginase isoforms in murine bone marrow-derived macrophages (BMMPhi) in the context of Th1 and Th2 stimulation. Surprisingly, in the presence of either Th2 cytokines or Th2 cells, we observe a specific induction of the hepatic isoform arginase I in BMMPhi. Induction of arginase I was shown on the mRNA and protein levels and obeyed the recently demonstrated synergism among the Th2 cytokines IL-4 and IL-10. Arginase II was detectable in unstimulated BMMPhi and was not significantly modulated by Th1 or Th2 stimulation. Similar to murine BMMPhi, murine bone marrow-derived dendritic cells, as well as a dendritic cell line, up-regulated arginase I expression and arginase activity upon Th2 stimulation, whereas arginase II was never detected. In addition to revealing the unexpected expression of arginase I in the macrophage/monocyte lineage, these results uncover a further intriguing parallelism between iNOS and arginase: both have a constitutive and an inducible isoform, the latter regulated by the Th1/Th2 balance.

Regulation of T cell receptor (TCR) beta gene expression by CD3 complex signaling in immature thymocytes: implications for TCRbeta allelic exclusion.

During alphabeta thymocyte development, clonotype-independent CD3 complexes are expressed at the cell surface before the pre-T cell receptor (TCR). Signaling through clonotype-independent CD3 complexes is required for expression of rearranged TCRbeta genes. On expression of a TCRbeta polypeptide chain, the pre-TCR is assembled, and TCRbeta locus allelic exclusion is established. We investigated the putative contribution of clonotype-independent CD3 complex signaling to TCRbeta locus allelic exclusion in mice single-deficient or double-deficient for CD3zeta/eta and/or p56(lck). These mice display defects in the expression of endogenous TCRbeta genes in immature thymocytes, proportional to the severity of CD3 complex malfunction. Exclusion of endogenous TCRbeta VDJ (variable, diversity, joining) rearrangements by a functional TCRbeta transgene was severely compromised in the single-deficient and double-deficient mutant mice. In contrast to wild-type mice, most of the CD25(+) double-negative (DN) thymocytes of the mutant mice failed to express the TCRbeta transgene, suggesting defective expression of the TCRbeta transgene similar to endogenous TCRbeta genes. In the mutant mice, a proportion of CD25(+) DN thymocytes that failed to express the transgene expressed endogenous TCRbeta polypeptide chains. Many double-positive cells of the mutant mice coexpressed endogenous and transgenic TCRbeta chains or more than one endogenous TCRbeta chain. The data suggest that signaling through clonotype-independent CD3 complexes may contribute to allelic exclusion of the TCRbeta locus by inducing the expression of rearranged TCRbeta genes in CD25(+) DN thymocytes.

Reduced generation but efficient TCR beta-chain selection of CD4+8+ double-positive thymocytes in mice with compromised CD3 complex signaling.

Maturation to the CD4+8+ double-positive (DP) stage of thymocyte development is restricted to cells that have passed TCRbeta selection, an important checkpoint at which immature CD4-8- double-negative (DN) cells that express TCRbeta polypeptide chains are selected for further maturation. The generation of DP thymocytes following TCRbeta selection is dependent on cellular survival, differentiation, and proliferation, and the entire process appears to be mediated by the pre-TCR/CD3 complex. In this study, we investigate the signaling requirements for TCRbeta selection using mice single deficient and double deficient for CD3zeta/eta and/or p56lck. While the numbers of DP cells are strongly reduced in the single-deficient mice, a further drastic reduction in the generation of DP thymocytes is seen in the double-deficient mice. The poor generation of DP cells in the mutant mice is primarily due to an impaired ability of CD25+ DN thymocytes to proliferate following expression of a TCRbeta-chain. Nevertheless, the residual DP cells in all mutant mice are strictly selected for expression of TCRbeta polypeptide chains. DN thymocytes of mutant mice expressed TCRbeta and CD3epsilon at the cell surface and contained mRNA for pre-Talpha, but not for clonotypic TCRalpha-chains, together suggesting that TCRbeta selection is mediated by pre-TCR signaling in all cases. The data suggest differential requirements of pre-TCR signaling for cell survival on the one hand, and for the proliferative burst associated with TCRbeta selection on the other.

A giant protease with potential to substitute for some functions of the proteasome.

An alanyl-alanyl-phenylalanyl-7-amino-4-methylcoumarin-hydrolyzing protease particle copurifying with 26S proteasomes was isolated and identified as tripeptidyl peptidase II (TPPII), a cytosolic subtilisin-like peptidase of unknown function. The particle is larger than the 26S proteasome and has a rod-shaped, dynamic supramolecular structure. TPPII exhibits enhanced activity in proteasome inhibitor-adapted cells and degrades polypeptides by exo- as well as predominantly trypsin-like endoproteolytic cleavage. TPPII may thus participate in extralysosomal polypeptide degradation and may in part account for nonproteasomal epitope generation as postulated for certain major histocompatibility complex class I alleles. In addition, TPPII may be able to substitute for some metabolic functions of the proteasome.

The specificity of proteasomes: impact on MHC class I processing and presentation of antigens.

We have studied polypeptide processing by purified proteasomes, with regard to proteolytic specificity and cytotoxic T-lymphocyte (CTL) epitope generation. Owing to defined preferences with respect to cleavage sites and fragment length, proteasomes degrade polypeptide substrates into cohorts of overlapping oligopeptides. Many of the proteolytic fragments exhibit structural features in common with major histocompatibility complex (MHC) class I ligands including fragment size and frequencies of amino acids at fragment boundaries. Proteasomes frequently generate definitive MHC class I ligands and/or slightly longer peptides, while substantially larger peptides are rare. Individual CTL epitopes are produced in widely varying amounts, often consistent with immunohierarchies among CTL epitopes. We further found that polypeptide processing is remarkably conserved among proteasomes of eukaryotic origin and that invertebrate proteasomes can efficiently produce known high-copy MHC class I ligands, suggesting evolutionary adaptation of the transporter associated with antigen processing and MHC class I to ancient constraints imposed by proteasomal protein degradation.

Requirement of CD3 complex-associated signaling functions for expression of rearranged T cell receptor beta VDJ genes in early thymic development.

During alpha beta thymocyte development, the clonotypic alpha beta-T cell receptor (TCR) is preceded by sequentially expressed immature versions of the TCR-CD3 complex: the pre-TCR, containing a clonotypic TCR-beta chain and invariant pre-Talpha, is expressed on pre-T cells before rearrangement of the TCR-alpha locus. Moreover, clonotype-independent CD3 complexes (CIC) appear on pro-T cells before VDJ rearrangements of TCR-beta genes. The pre-TCR is known to mediate TCR-beta selection, the prerequisite for maturation of CD4(-)8(-) double negative (DN) thymocytes to the CD4(+)8(+) double positive stage. A developmental function of CIC has so far not been delineated. In mice single deficient and double deficient for CD3zeta/eta and/or p56(lck), we observe a pronounced reduction in the proportions of CD25(+) DN thymocytes that express intracellular TCR-beta chains. TCR-beta transcripts are reduced in parallel with TCR-beta polypeptide chains whereas no reduction in TCR-beta locus rearrangements could be detected. Wild-type levels of TCR-beta transcripts and of cells expressing TCR-beta polypeptide chains are induced by treatment with anti-CD3epsilon mAb. The data suggest that the initial expression of rearranged TCR-beta VDJ genes in pro-T cell to pre-T cell progression is dependent on CD3 complex signaling, and thus define a putative developmental function for CIC.

Murine macrophages secrete interferon gamma upon combined stimulation with interleukin (IL)-12 and IL-18: A novel pathway of autocrine macrophage activation.

Interferon (IFN)-gamma, a key immunoregulatory cytokine, has been thought to be produced solely by activated T cells and natural killer cells. In this study, we show that murine bone marrow- derived macrophages (BMMPhi) secrete large amounts of IFN-gamma upon appropriate stimulation. Although interleukin (IL)-12 and IL-18 alone induce low levels of IFN-gamma mRNA transcripts, the combined stimulation of BMMPhi with both cytokines leads to the efficient production of IFN-gamma protein. The macrophage-derived IFN-gamma is biologically active as shown by induction of inducible nitric oxide synthase as well as upregulation of CD40 in macrophages. Our findings uncover a novel pathway of autocrine macrophage activation by demonstrating that the macrophage is not only a key cell type responding to IFN-gamma but also a potent IFN-gamma-producing cell.

Alternative metabolic states in murine macrophages reflected by the nitric oxide synthase/arginase balance: competitive regulation by CD4+ T cells correlates with Th1/Th2 phenotype.

Activated murine macrophages metabolize L-arginine via two main pathways that are catalyzed by the inducible enzymes nitric oxide synthase (iNOS) and arginase. We have previously shown that CD4+ T cell-derived cytokines regulate a competitive balance in the expression of both enzymes in macrophages; Thl-type cytokines induce iNOS while they inhibit arginase, whereas the reverse is the case for Th2-type cytokines. Here we addressed the regulation of both metabolic pathways by CD4+ T cells directly. Macrophages were used as APCs for established Th1 and Th2 T cell clones as well as for in vitro polarized Th1 or Th2 T cells of transgenic mice bearing an MHC class II-restricted TCR. Both systems revealed a similar dichotomy in the macrophages; Th1 T cells led to an exclusive induction of iNOS, whereas Th2 T cells up-regulated arginase without inducing iNOS. Arginase levels induced by Th2 T cells far exceeded those inducible by individual Th2 cytokines. Similarly, high arginase levels could be induced by supernatants of Th2 cells stimulated in various ways. Ab blocking experiments revealed the critical importance of IL-4 and IL-10 for arginase up-regulation. Finally, strong synergistic effects between IL-4/IL-13 and IL-10 were observed, sufficient to account for the extraordinarily high arginase activity induced by Th2 cells. Our results suggest that the iNOS/arginase balance in macrophages is competitively regulated in the context of Th1- vs Th2-driven immune reactions, most likely by cytokines without the requirement for direct cell interaction.

Herpesvirus saimiri-transformed human CD4+ T-cell lines: an efficient target cell system for the analysis of human immunodeficiency virus-specific cytotoxic CD8+ T-lymphocyte activity.

Herpesvirus saimiri growth-transformed human CD4+ T lymphocytes were examined for their suitability as a target cell system for investigating human immunodeficiency virus (HIV)-specific HLA class I-restricted cytotoxic T-cell activity. Besides CD4, they express the chemokine receptors CCR5 and CXCR4, the common coreceptors of HIV. They are infectible by a range of HIV strains, including primary isolates, becoming efficient targets for CD8-positive HIV-specific cytotoxic T lymphocytes.