The MHC and the Recognition of Self and Altered Self in Experimental and Rheumatoid Arthritis

The Major histocompatibility complex (MHC) is a highly polymorphic and genedense region on chromosome 6 in humans and 20 in the rat. Genes in the MHC are the major risk factor for the development of autoimmunity. Rheumatoid arthritis (RA) is a common autoimmune disease with a strong association to a specific subset of HLADRB1 alleles, which encode a shared amino acid motif in the HLA-DR! chain. This shared epitope (SE) contributes to the formation of the P4 pocket in the peptide-binding groove of the HLA-DR complex. Recently, two weaker associations to the MHC class I gene HLA-B and to a second MHC class II gene, HLA-DPB1, have been identified. Whereas the dissection of the genetic association between autoimmunity and the MHC has progressed rapidly in the last decade, the functional role of the MHC genes in the development of autoimmunity has not yet been resolved to the same extent. The work presented in this thesis represents some of our efforts to contribute to this understanding. Paper I describes our attempts to induce arthritis with "-enolase and citrullinated "-enolase in HLA-DR4 transgenic mice. Based on the strong genetic association between antibodies to citrullinated "-enolase peptide 1 (CEP-1) and HLA-DRB1 SE alleles, we aimed to identify if anti-CEP-1 antibodies can be induced in mice transgenic for a human HLA-DRB1 SE allele, and if this would depend on a citrullinated HLADRB1* 0401 restricted T cell epitope. We could neither prove that native or citrullinated "-enolase induced arthritis nor did we observe a citrulline specific B or T cell response. In Paper II we investigated the relevance and the extent of joint-directed anticitrulline immunity in RA. We identified two citrullinated antibody epitopes on type II collagen (CII) present in 17% and 21% of RA patients. Anti-citrullinated CII reactivity partly overlapped with the reactivity towards CEP-1, however only antibodies directed to citrullinated CII bound to RA cartilage specimens. This suggests that antibodies directed to citrullinated CII may contribute to the inflammatory process in the joints. Paper III-V summarizes our work concerning the influence of allelic variation in the rat MHC on T cell selection, MHC expression and susceptibility to autoimmune arthritis. Paper III introduces our panel of intra-MHC congenic strains and demonstrates that an interaction between the RT1-A genes in the MHC class I and Tap2 in the MHC class II region regulates the negative selection of CD8 T cells. The RT1-A genes are part of a haplotype designated T cell selection QTL-1 (Tcs1), whereas Tap2 is in linkage disequilibrium with the MHC class II genes, in the locus designated T cell selection QTL-2 (Tcs2). In Paper IV we evaluated the impact of these two QTL on the regulation of Pristane-induced arthritis (PIA). Allelic variation in Tcs1 did not influence PIA, whereas Tcs2 regulated the onset and the severity of PIA. A comparison of the amino acid polymorphisms between the haplotypes as well as functional studies suggested a major contribution of the HLA-DQ homolog RT1-B to the development of PIA. It has earlier been demonstrated that pristane-primed CD4 T cells transfer arthritis in naive recipients. To investigate how the MHC-II haplotype affects T cell priming and the subsequent PIA development, we characterized the T cell compartment after pristane administration. The frequency of Th1 cells correlated with an early onset of PIA and reduced arthritis severity in one haplotype was associatedwith a high ratio of T regulatory to T effector cells. These results are presented in Paper V

Redox-Responsive Nanocarrier for Controlled Release of Drugs in Inflammatory Skin Diseases

A synthetic route for redox-sensitive and non-sensitive core multi-shell (CMS) carriers with sizes below 20 nm and narrow molecular weight distributions was established. Cyclic voltammetric measurements were conducted characterizing the redox potentials of reduction-sensitive CMS while showcasing its reducibility through glutathione and tris(2-carboxyethyl)-phosphine as a proof of concept. Measurements of reduction-initiated release of the model dye Nile red by time-dependent fluorescence spectroscopy showed a pronounced release for the redox-sensitive CMS nanocarrier (up to 90% within 24 h) while the non-sensitive nanocarriers showed no release in PBS. Penetration experiments using ex vivo human skin showed that the redox-sensitive CMS nanocarrier could deliver higher percentages of the loaded macrocyclic dye meso-tetra (m-hydroxyphenyl) porphyrin (mTHPP) to the skin as compared to the non-sensitive CMS nanocarrier. Encapsulation experiments showed that these CMS nanocarriers can encapsulate dyes or drugs with different molecular weights and hydrophobicity. A drug content of 1 to 6 wt% was achieved for the anti-inflammatory drugs dexamethasone and rapamycin as well as fluorescent dyes such as Nile red and porphyrins. These results show that redox-initiated drug release is a promising strategy to improve the topical drug delivery of macrolide drugs

Некоторые аспекты эффективности обучения при переходе от очной формы обучения к дистанционной

ВЫСШЕЕ МЕДИЦИНСКОЕ ОБРАЗОВАНИЕОБРАЗОВАНИЕ МЕДИЦИНСКОЕ /МЕТОДЫОЧНАЯ ФОРМА ОБУЧЕНИЯЗАОЧНАЯ ФОРМА ОБУЧЕНИЯДИСТАНЦИОННОЕ ОБУЧЕНИЕ /МЕТОДЫОБРАЗОВАТЕЛЬНЫЙ ПРОЦЕССХИМИЯ (ДИСЦИПЛИНА

Geometric representations for minimalist grammars

We reformulate minimalist grammars as partial functions on term algebras for strings and trees. Using filler/role bindings and tensor product representations, we construct homomorphisms for these data structures into geometric vector spaces. We prove that the structure-building functions as well as simple processors for minimalist languages can be realized by piecewise linear operators in representation space. We also propose harmony, i.e. the distance of an intermediate processing step from the final well-formed state in representation space, as a measure of processing complexity. Finally, we illustrate our findings by means of two particular arithmetic and fractal representations.Comment: 43 pages, 4 figure

ADP-ribosylation of arginine

Arginine adenosine-5′-diphosphoribosylation (ADP-ribosylation) is an enzyme-catalyzed, potentially reversible posttranslational modification, in which the ADP-ribose moiety is transferred from NAD+ to the guanidino moiety of arginine. At 540 Da, ADP-ribose has the size of approximately five amino acid residues. In contrast to arginine, which, at neutral pH, is positively charged, ADP-ribose carries two negatively charged phosphate moieties. Arginine ADP-ribosylation, thus, causes a notable change in size and chemical property at the ADP-ribosylation site of the target protein. Often, this causes steric interference of the interaction of the target protein with binding partners, e.g. toxin-catalyzed ADP-ribosylation of actin at R177 sterically blocks actin polymerization. In case of the nucleotide-gated P2X7 ion channel, ADP-ribosylation at R125 in the vicinity of the ligand-binding site causes channel gating. Arginine-specific ADP-ribosyltransferases (ARTs) carry a characteristic R-S-EXE motif that distinguishes these enzymes from structurally related enzymes which catalyze ADP-ribosylation of other amino acid side chains, DNA, or small molecules. Arginine-specific ADP-ribosylation can be inhibited by small molecule arginine analogues such as agmatine or meta-iodobenzylguanidine (MIBG), which themselves can serve as targets for arginine-specific ARTs. ADP-ribosylarginine specific hydrolases (ARHs) can restore target protein function by hydrolytic removal of the entire ADP-ribose moiety. In some cases, ADP-ribosylarginine is processed into secondary posttranslational modifications, e.g. phosphoribosylarginine or ornithine. This review summarizes current knowledge on arginine-specific ADP-ribosylation, focussing on the methods available for its detection, its biological consequences, and the enzymes responsible for this modification and its reversal, and discusses future perspectives for research in this field

Natural Polymorphisms in Tap2 Influence Negative Selection and CD4 : CD8 Lineage Commitment in the Rat

Contains fulltext : 136368.pdf (publisher's version ) (Open Access)Genetic variation in the major histocompatibility complex (MHC) affects CD4ratioCD8 lineage commitment and MHC expression. However, the contribution of specific genes in this gene-dense region has not yet been resolved. Nor has it been established whether the same genes regulate MHC expression and T cell selection. Here, we assessed the impact of natural genetic variation on MHC expression and CD4ratioCD8 lineage commitment using two genetic models in the rat. First, we mapped Quantitative Trait Loci (QTLs) associated with variation in MHC class I and II protein expression and the CD4ratioCD8 T cell ratio in outbred Heterogeneous Stock rats. We identified 10 QTLs across the genome and found that QTLs for the individual traits colocalized within a region spanning the MHC. To identify the genes underlying these overlapping QTLs, we generated a large panel of MHC-recombinant congenic strains, and refined the QTLs to two adjacent intervals of approximately 0.25 Mb in the MHC-I and II regions, respectively. An interaction between these intervals affected MHC class I expression as well as negative selection and lineage commitment of CD8 single-positive (SP) thymocytes. We mapped this effect to the transporter associated with antigen processing 2 (Tap2) in the MHC-II region and the classical MHC class I gene(s) (RT1-A) in the MHC-I region. This interaction was revealed by a recombination between RT1-A and Tap2, which occurred in 0.2% of the rats. Variants of Tap2 have previously been shown to influence the antigenicity of MHC class I molecules by altering the MHC class I ligandome. Our results show that a restricted peptide repertoire on MHC class I molecules leads to reduced negative selection of CD8SP cells. To our knowledge, this is the first study showing how a recombination between natural alleles of genes in the MHC influences lineage commitment of T cells

Redox-Responsive Nanocarrier for Controlled Release of Drugs in Inflammatory Skin Diseases

A synthetic route for redox-sensitive and non-sensitive core multi-shell (CMS) carriers with sizes below 20 nm and narrow molecular weight distributions was established. Cyclic voltammetric measurements were conducted characterizing the redox potentials of reduction-sensitive CMS while showcasing its reducibility through glutathione and tris(2-carboxyethyl)-phosphine as a proof of concept. Measurements of reduction-initiated release of the model dye Nile red by time-dependent fluorescence spectroscopy showed a pronounced release for the redox-sensitive CMS nanocarrier (up to 90% within 24 h) while the non-sensitive nanocarriers showed no release in PBS. Penetration experiments using ex vivo human skin showed that the redox-sensitive CMS nanocarrier could deliver higher percentages of the loaded macrocyclic dye meso-tetra (m-hydroxyphenyl) porphyrin (mTHPP) to the skin as compared to the non-sensitive CMS nanocarrier. Encapsulation experiments showed that these CMS nanocarriers can encapsulate dyes or drugs with different molecular weights and hydrophobicity. A drug content of 1 to 6 wt% was achieved for the anti-inflammatory drugs dexamethasone and rapamycin as well as fluorescent dyes such as Nile red and porphyrins. These results show that redox-initiated drug release is a promising strategy to improve the topical drug delivery of macrolide drugs

Versatile control over size and spacing of small mesopores in metal oxide films and catalytic coatings via templating with hyperbranched core-multishell polymers

Controlling the pore structure of metal oxide films and supported catalysts is an essential requirement for tuning their functionality and long-term stability. Typical synthesis concepts such as “Evaporation Induced Self Assembly” rely on micelle formation and self assembly. These processes are dynamic in nature and therefore strongly influenced by even slight variations in the synthesis conditions. Moreover, the synthesis of very small mesopores (2–5 nm) and independent control over the thickness of pore walls are very difficult to realize with micelle-based approaches. In this contribution, we present a novel approach for the synthesis of mesoporous metal oxide films and catalytic coatings with ordered porosity that decouples template formation and film deposition by use of hyperbranched core–multishell polymers as templates. The approach enables independent control of pore size, wall thickness and the content of catalytically active metal particles. Moreover, dual templating with a combination of hyperbranched core–multishell polymers and micelles provides facile access to hierarchical bimodal porosity. The developed approach is illustrated by synthesizing one of the most common metal oxides (TiO2) and a typical supported catalyst (PdNP/TiO2). Superior catalyst performance is shown for the gas-phase hydrogenation of butadiene. The concept provides a versatile and general platform for the rational optimization of catalysts based e.g. on computational prediction of optimal pore structures and catalyst compositions.BMBF, 03EK3009, Design hocheffizienter Elektrolysekatalysatore

Self-reactive T cells induce and perpetuate chronic relapsing arthritis

Background: CD4+ T cells play a central role during the early stages of rheumatoid arthritis (RA), but to which extent they are required for the perpetuation of the disease is still not fully understood. The aim of the current study was to obtain conclusive evidence that T cells drive chronic relapsing arthritis. Methods: We used the rat pristane-induced arthritis model, which accurately portrays the chronic relapsing-remitting disease course of RA, to examine the contribution of T cells to chronic arthritis. Results: Rats subjected to whole-body irradiation and injected with CD4+ T cells from lymph nodes of pristane-injected donors developed chronic arthritis that lasted for more than 4 months, whereas T cells from the spleen only induced acute disease. Thymectomy in combination with irradiation enhanced the severity of arthritis, suggesting that sustained lymphopenia promotes T cell-driven chronic inflammation in this model. The ability of T cells to induce chronic arthritis correlated with their expression of Th17-associated transcripts, and while depletion of T cells in rats with chronic PIA led to transient, albeit significant, reduction in disease, neutralization of IL-17 resulted in almost complete and sustained remission. Conclusion: These findings show that, once activated, self-reactive T cells can sustain inflammatory responses for extended periods of time and suggest that such responses are promoted in the presence of IL-17