Truncation of the class II beta-chain cytoplasmic domain influences the level of class II/invariant chain-derived peptide complexes.

Previous studies have established that antigen presenting cells (APC) expressing major histocompatibility complex class II beta chains with truncated cytoplasmic domains are impaired in their capacity to activate T cells. While it had been widely accepted that this impairment is due to a defect in class II cytoplasmic domain-dependent signal transduction, we recently generated transgenic mice expressing only truncated class II beta chains, and functional analyses of APC from these mice revealed signaling-independent defects in antigen presentation. Here, we demonstrate that T cells primed on such transgenic APC respond better to stimulation by APC expressing truncated beta chains than by wild-type APC. This finding suggests that APC expressing truncated class II beta chains are not inherently defective in their antigen presenting capacity but, rather, may differ from wild-type APC in the peptide antigens that they present. Indeed, analysis of the peptides bound to class II molecules isolated from normal and transgenic spleen cells revealed clear differences. Most notably, the level of class II-associated invariant chain-derived peptides (CLIP) is significantly reduced in cells expressing only truncated beta chains. Prior studies have established that CLIP and antigenic peptides compete for binding to class II molecules. Thus, our results suggest that the cytoplasmic domain of the class II beta chain affects antigen presentation by influencing the level of CLIP/class II complexes.

Genetic analysis of type 1 diabetes using whole genome approaches.

Whole genome linkage analysis of type 1 diabetes using affected sib pair families and semi-automated genotyping and data capture procedures has shown how type 1 diabetes is inherited. A major proportion of clustering of the disease in families can be accounted for by sharing of alleles at susceptibility loci in the major histocompatibility complex on chromosome 6 (IDDM1) and at a minimum of 11 other loci on nine chromosomes. Primary etiological components of IDDM1, the HLA-DQB1 and -DRB1 class II immune response genes, and of IDDM2, the minisatellite repeat sequence in the 5' regulatory region of the insulin gene on chromosome 11p15, have been identified. Identification of the other loci will involve linkage disequilibrium mapping and sequencing of candidate genes in regions of linkage.

HLA-Cw allele analysis by PCR-restriction fragment length polymorphism: study of known and additional alleles.

We describe a technique for HLA-Cw genotyping by digestion of PCR-amplified genes with restriction endonucleases. Locus-specific primers selectively amplified HLA-Cw sequences from exon 2 in a single PCR that avoided coamplification of other classical and nonclassical class I genes. Amplified DNAs were digested with selected enzymes. Sixty-three homozygous cell lines from International Histocompatibility Workshop X and 113 unrelated individual cells were genotypes for HLA-Cw and compared with serology. The present protocol can distinguish 23 alleles corresponding to the known HLA-Cw sequences. Genotyping of serologically undetectable alleles (HLA-Cw Blank) and of heterozygous cells was made possible by using this method. Six additional HLA-Cw alleles were identified by unusual restriction patterns and confirmed by sequencing; this observation suggests the presence of another family of allele-sharing clusters in the HLA-B locus. This PCR-restriction endonuclease method provides a simple and convenient approach for HLA-Cw DNA typing, allowing the definition of serologically undetectable alleles, and will contribute to the evaluation of the biological role of the HLA-C locus.

Restricted and conserved T-cell repertoires involved in allorecognition of class II major histocompatibility complex.

The nature of the alloreactive T-cell response is not yet clearly understood. These strong cellular responses are thought to be the basis of allograft rejection and graft-vs.-host disease. The question of the extent of responding T-cell repertoires has so far been addressed by cellular cloning, often combined with molecular T-cell receptor (TCR) analysis. Here we present a broad repertoire analysis of primed responder cells from mixed lymphocyte cultures in which two different DR1/3 responders were stimulated with DR3/4 cells. Repertoire analysis was performed by TCR spectratyping, a method by which T cells are analyzed on the basis of the complementarity-determining region 3 length of different variable region (V) families. Strikingly, both responders showed very similar repertoires when the TCR V beta was used as a lineage marker. This was not seen when TCR V alpha was analyzed. A different pattern of TCR V beta was observed if the stimulating alloantigen was changed. This finding indicates that alloreactive T cells form a specific repertoire for each alloantigen. Since conservation appears to be linked to TCR V beta, the question of different roles of alpha and beta chains in allorecognition is raised.

Similarities and differences in signal transduction by interleukin 4 and interleukin 13: analysis of Janus kinase activation.

The cytokines interleukin (IL) 4 and IL-13 induce many of the same biological responses, including class switching to IgE and induction of major histocompatibility complex class II antigens and CD23 on human B cells. It has recently been shown that IL-4 induces the tyrosine phosphorylation of a 170-kDa protein, a substrate called 4PS, and of the Janus kinase (JAK) family members JAK1 and JAK3. Because IL-13 has many functional effects similar to those of IL-4, we compared the ability of IL-4 and IL-13 to activate these signaling molecules in the human multifactor-dependent cell line TF-1. In this report we demonstrate that both IL-4 and IL-13 induced the tyrosine phosphorylation of 4PS and JAK1. Interestingly, although IL-4 induced the tyrosine phosphorylation of JAK3, we did not detect JAK3 phosphorylation in response to IL-13. These data suggest that IL-4 and IL-13 signal in similar ways via the activation of JAK1 and 4PS. However, our data further indicate that there are significant differences because IL-13 does not activate JAK3.

Low major histocompatibility complex class II diversity in European and North American moose.

Major histocompatibility complex (MHC) genes encode cell surface proteins whose function is to bind and present intracellularly processed peptides to T lymphocytes of the immune system. Extensive MHC diversity has been documented in many species and is maintained by some form of balancing selection. We report here that both European and North American populations of moose (Alces alces) exhibit very low levels of genetic diversity at an expressed MHC class II DRB locus. The observed polymorphism was restricted to six amino acid substitutions, all in the peptide binding site, and four of these were shared between continents. The data imply that the moose have lost MHC diversity in a population bottleneck, prior to the divergence of the Old and New World subspecies. Sequence analysis of mtDNA showed that the two subspecies diverged at least 100,000 years ago. Thus, viable moose populations with very restricted MHC diversity have been maintained for a long period of time. Both positive selection for polymorphism and intraexonic recombination have contributed to the generation of MHC diversity after the putative bottleneck.

Expression cloning of dSR-CI, a class C macrophage-specific scavenger receptor from Drosophila melanogaster.

Mammalian class A macrophage-specific scavenger receptors (SR-A) exhibit unusually broad binding specificity for a wide variety of polyanionic ligands. The properties of these receptors suggest that they may be involved in atherosclerosis and host defense. We have previously observed a similar receptor activity in Drosophila melanogaster embryonic macrophages and in the Drosophila macrophage-like Schneider L2 cell line. Expression cloning was used to isolate from L2 cells a cDNA that encodes a third class (class C) of scavenger receptor, Drosophila SR-CI (dSR-CI). dSR-CI expression was restricted to macrophages/hemocytes during embryonic development. When expressed in mammalian cells, dSR-CI exhibited high affinity and saturable binding of 125I-labeled acetylated low density lipoprotein and mediated its chloroquine-dependent, presumably lysosomal, degradation. Although the broad polyanionic ligand-binding specificity of dSR-CI was similar to that of SR-A, their predicted protein sequences are not similar. dSR-CI is a 609-residue type I integral membrane protein containing several well-known sequence motifs, including two complement control protein (CCP) domains and somatomedin B, MAM, and mucin-like domains. Macrophage scavenger receptors apparently mediate important, well-conserved functions and may be pattern-recognition receptors that arose early in the evolution of host-defense mechanisms. Genetic and physiologic analysis of dSR-CI function in Drosophila should provide further insights into the roles played by scavenger receptors in host defense and development.

Latent tuberculosis infection : a diagnostic challenge : Tuberculin skin testing versus interferon-γ release assays

Trabalho Final do Curso de Mestrado Integrado em Medicina, Faculdade de Medicina, Universidade de Lisboa, 2014

Explora: A Visualisation Tool for Metric Analysis of Software Corpora

When analysing software metrics, users find that visualisation tools lack support for (1) the detection of patterns within metrics; and (2) enabling analysis of software corpora. In this paper we present Explora, a visualisation tool designed for the simultaneous analysis of multiple metrics of systems in software corpora. Explora incorporates a novel lightweight visualisation technique called PolyGrid that promotes the detection of graphical patterns. We present an example where we analyse the relation of subtype polymorphism with inheritance and invocation in corpora of Smalltalk and Java systems and find that (1) subtype polymorphism is more likely to be found in large hierarchies; (2) as class hierarchies grow horizontally, they also do so vertically; and (3) in polymorphic hierarchies the length of the name of the classes is orthogonal to the cardinality of the call sites.

Notes on functional analysis.

"These notes ... are intended only for the convenience of the students in mathematics 515-516 and are not intended to be considered as a text on the subject matter."

The people's money. A brief analysis of the present position in America.

Mode of access: Internet.

Synthesis dataset of physical and ecosystem properties from pan-arctic wetland sites using peat core analysis

Permafrost dynamics play an important role in high-latitude peatland carbon balance and are key to understanding the future response of soil carbon stocks. Permafrost aggradation can control the magnitude of the carbon feedback in peatlands through effects on peat properties. We compiled peatland plant macrofossil records for the northern permafrost zone (515 cores from 280 sites) and classified samples by vegetation type and environmental class (fen, bog, tundra and boreal permafrost, thawed permafrost). We examined differences in peat properties (bulk density, carbon (C), nitrogen (N) and organic matter content, C/N ratio) and C accumulation rates among vegetation types and environmental classes.

Social Support Networks and Self-Efficacy of Peruvian Women Diagnosed with Cancer: A Biocultural Analysis of Health Behavior Constructs

Thesis (Ph.D.)--University of Washington, 2016-06

Regulation of dendrite growth, placement, and patterning in Drosophila melanogaster class 4 dendrite arborization neurons

Thesis (Ph.D.)--University of Washington, 2016-06