Cellular entry of HIV: Evaluation of therapeutic targets.

In the absence of a vaccine which could stop the HIV/AIDS pandemic, the development of therapeutic options is of utmost interest. The combined use of inhibitors of reverse transcriptase and protease as highly active antiretroviral therapy (HAART) provided the first effective treatment of HIV/AIDS and significantly decreased the number of AIDS related deaths in industrialized countries. However, the emergence of resistant viruses and the toxic side effects of HAART highlights that novel therapies are urgently required.

Preconditional activation of hypoxia-inducible factors ameliorates ischemic acute renal failure.

Activation of hypoxia-inducible transcription factor (HIF) has been identified as an important mechanism of cellular adaptation to low oxygen. Normoxic degradation of HIF is mediated by oxygen-dependent hydroxylation of specific prolyl residues of the regulative alpha-subunits by HIF prolyl hydroxylases (PHD). It was hypothesized that inhibition of HIF degradation by either hypoxia or pharmacologic inhibition of PHD would confer protection against subsequent ischemic injury.

T cell activation as starter and motor of rheumatic inflammation.

Rheumatic inflammation is driven by sustained specific immunity against self-antigens, resulting in local inflammation and cellular infiltration and, subsequently, in tissue damage. Although the specific autoantigen(s) eliciting the detrimental immune reactions in rheumatic diseases have rarely been defined, it has become clear that the mechanisms resulting in the destruction of tissue and the loss of organ function during the course of the diseases are essentially the same as in protective immunity against invasive microorganisms. Of fundamental importance in initiating, controlling, and driving these specific immune responses are CD4 T cells.

Association of the IL4R single-nucleotide polymorphism I50V with rapidly erosive rheumatoid arthritis.

Objective: To examine whether single-nucleotide polymorphisms (SNPs) of the interleukin-4 receptor gene IL4R influence susceptibility to, or radiographic progression in, rheumatoid arthritis (RA).

Methods: The contribution of 2 SNPs (I50V and Q551R) in the coding region of IL4R to RA susceptibility was analyzed by allele-specific polymerase chain reaction in a case-control study of 471 RA patients and 371 healthy controls. Patients with available radiographs of the hands and feet obtained 2 years after disease onset (n = 302) were stratified retrospectively according to radiologic outcome into an erosive and a nonerosive group to evaluate the association between IL4R SNPs and disease progression.

IFNGR1 single nucleotide polymorphisms in rheumatoid arthritis.

On the basis of their biological function, potential genetic candidates for susceptibility to rheumatoid arthritis can be postulated. IFNGR1, encoding the ligand-binding chain of the receptor for interferon gamma, IFNgammaR1, is one such gene because interferon gamma is involved in the pathogenesis of the disease. In the coding sequence of IFNGR1, two nucleotide positions have been described to be polymorphic in the Japanese population.

Nucleo-cytoplasmic distribution of beta-catenin is regulated by retention.

beta-catenin is the central signalling molecule of the canonical Wnt pathway, where it activates target genes in a complex with LEF/TCF transcription factors in the nucleus. The regulation of beta-catenin activity is thought to occur mainly on the level of protein degradation, but it has been suggested that beta-catenin nuclear localization and hence its transcriptional activity may additionally be regulated via nuclear import by TCF4 and BCL9 and via nuclear export by APC and axin. Using live-cell microscopy and fluorescence recovery after photobleaching (FRAP), we have directly analysed the impact of these factors on the subcellular localization of beta-catenin, its nucleo-cytoplasmic shuttling and its mobility within the nucleus and the cytoplasm.

The p38 mitogen-activated protein kinase signaling cascade in CD4 T cells.

Since the identification of the p38 mitogen-activated protein kinase (MAPK) as a key signal-transducing molecule in the expression of the proinflammatory cytokine tumor necrosis factor (TNF) more than 10 years ago, huge efforts have been made to develop inhibitors of p38 MAPK with the intent to modulate unwanted TNF activity in diseases such as autoimmune diseases or sepsis. However, despite some anti-inflammatory effects in animal models, no p38 MAPK inhibitor has yet demonstrated clinical efficacy in human autoimmune disorders. One possible reason for this paradox might relate to the fact that the p38 MAPK signaling cascade is involved in the functional regulation of several different cell types that all contribute to the complex pathogenesis of human autoimmune diseases.

Powered by pairing: the surrogate light chain amplifies immunoglobulin heavy chain signaling and pre-selects the antibody repertoire.

Selective expansion of functional pre-B cells is accomplished by the assembly of a signaling-competent pre-B cell receptor (pre-BCR) consisting of immunoglobulin mu heavy chains (muHC), surrogate light chains (SLC) and Igalpha/Igbeta. Here, we review recent data showing that muHCs, in the absence of SLC, deliver autonomous differentiation signals. However, enhanced signaling necessary for pre-B cell expansion requires cross-linking of pre-BCRs via the non-immunoglobulin tail of SLC's subunit lambda5.

Truncated APC is required for cell proliferation and DNA replication.

The tumour suppressor APC is truncated in most colon cancers, which leads to the stabilization of beta-catenin and to the constitutive activation of Wnt signalling. However, it is not clear why colon cancer cells retain the truncated APC fragment. Here, we show that a decrease of APC levels achieved by RNA interference impairs cell proliferation and DNA replication, not only in 293 cells that express a wild-type protein, but also in SW480 colon cancer cells that express exclusively a truncated APC fragment.

E-cadherin modulates Wnt-dependent transcription in colorectal cancer cells but does not alter Wnt-independent gene expression in fibroblasts.

E-cadherin mediates homophilic adhesion of epithelial cells and is a major determinant of epithelial differentiation during embryonic development and tumor progression. At cell junctions, E-cadherin associates with beta-catenin, which also functions as a transcriptional co-activator of the canonical Wnt signaling pathway by interacting with TCF transcription factors. Here, we have analyzed whether E-cadherin plays a role in the control of gene expression in Wnt-dependent and -independent cellular systems.

The p38 mitogen-activated protein kinase regulates effector functions of primary human CD4 T cells.

The role of p38 mitogen-activated protein kinase in primary human T cells is incompletely understood. We analyzed in detail the role of p38 in the regulation of effector functions and differentiation of human CD4 T cells by using a p38-specific inhibitor and a dominant-negative mutant of p38. p38 was found to mediate expression of IL-10 and the Th2 cytokines IL-4, IL-5, and IL-13 in both, primary naive and memory T cells.

The IL-4 receptor alpha-chain-binding cytokines, IL-4 and IL-13, induce forkhead box P3-expressing CD25+CD4+ regulatory T cells from CD25-CD4+ precursors.

The mechanisms underlying the extrathymic generation of CD25+CD4 regulatory T cells (Tregs) are largely unknown. In this study the IL-4R alpha-chain-binding cytokines, IL-4 and IL-13, were identified as inducers of CD25+ Tregs from peripheral CD25-CD4 naive T cells. IL-4-induced CD25+ Tregs phenotypically and functionally resemble naturally occurring Tregs in that they are anergic to mitogenic stimulation, inhibit the proliferation of autologous responder T cells, express high levels of the Forkhead box P3 and the surface receptors glucocorticoid-induced TNFR family-related protein and CTLA-4, and inhibit effector T cells in a contact-dependent, but cytokine-independent, manner.

The role of the Wnt signalling pathway in colorectal tumorigenesis.

Colorectal cancer (CRC) is the second largest cause of cancer-related deaths in Western countries. CRC arises from the colorectal epithelium as a result of the accumulation of genetic alterations in defined oncogenes and tumour suppressor genes. Mutations in the tumour suppressor APC (adenomatous polyposis coli) genes occur early in the development of CRC and lead to the stabilization of the Wnt pathway component beta-catenin and to the constitutive activation of Wnt signalling.

The evolution of human anti-double-stranded DNA autoantibodies.

It has been proposed that the anti-double-stranded DNA (dsDNA) response in patients with systemic lupus erythematosus (SLE) is antigen driven and that DNA or nucleosomes select anti-DNA reactive, somatically mutated B cells. We have used site-directed mutagenesis to systematically revert the somatic mutations of two human anti-dsDNA antibodies from SLE patients to analyze the resulting changes in DNA binding as well as binding to other autoantigens. Our data demonstrate that high-affinity binding to dsDNA and nucleosomes is acquired by somatic replacement mutations in a stepwise manner.

Regulatory T cells in rheumatoid arthritis.

Apart from the deletion of autoreactive T cells in the thymus, various methods exist in the peripheral immune system to control specific human immune responses to self-antigens. One of these mechanisms involves regulatory T cells, of which CD4+CD25+ T cells are a major subset. Recent evidence suggests that CD4+CD25+ T cells have a role in controlling the development of autoimmune diseases in animals and in humans.

The role of the T cell in autoimmune inflammation.

T cells, in particular CD4+ T cells, have been implicated in mediating many aspects of autoimmune inflammation. However, current evidence suggests that the role played by CD4+ T cells in the development of rheumatoid inflammation exceeds that of activated proinflammatory T-helper (Th)1 effector cells that drive the chronic autoimmune response. Subsets of CD4+ T cells with regulatory capacity, such as CD25+ regulatory T (Treg) cells and Th2 cells, have been identified, and recent observations suggest that in rheumatoid arthritis the function of these regulatory T cells is severely impaired.

Regulation of myeloid cell function and major histocompatibility complex class II expression by tumor necrosis factor.

Objective: Tumor necrosis factor (TNF)-neutralizing agents are the most successful means of ameliorating systemic autoimmune inflammation. Neutralization of TNF, however, is often associated with the development of autoantibodies, particularly to nuclear antigens, and the mechanisms of this are unknown. We undertook this study to analyze the effect of TNF and its neutralization on the expression of major histocompatibility complex class II molecules and on the function of antigen-presenting myeloid cells in rheumatoid arthritis (RA).

The Wnt connection to tumorigenesis.

Wnt signaling has been identified as one of the key signaling pathways in cancer, regulating cell growth, motility and differentiation. Because of its widespread activation in diverse human tumor diseases, the Wnt pathway has gained considerable and growing interest in tumor research over recent years. Evidence that altered Wnt signaling is important for human tumor development came from three major findings: (i) the tumor suppressor adenomatous polyposis coli (APC) binds to the Wnt pathway component beta-catenin and is involved in its degradation, (ii) mutations of APC in colon tumors lead to stabilization of the beta-catenin protein and (iii) tumor-associated mutations of beta-catenin in colorectal cancer as well as in other tumor types lead to its stabilisation, qualifying beta-catenin as a proto-oncogene.

Generation and regulation of human Th1-biased immune responses in vivo: a critical role for IL-4 and IL-10.

Tissue damage in many human autoimmune diseases is mediated by activated autoantigen-specific Th1 cells. Delineation of the regulatory mechanisms controlling a Th1-biased human immune reaction and its pathologic potential is, therefore, a critical step in the understanding of autoimmune diseases. In this study, we introduce a novel means to investigate human Th1-biased immune responses in vivo.

GATA-3 in human T cell helper type 2 development.

The delineation of the in vivo role of GATA-3 in human T cell differentiation is a critical step in the understanding of molecular mechanisms directing human immune responses. We examined T cell differentiation and T cell-mediated effector functions in individuals lacking one functional GATA-3 allele. CD4 T cells from GATA-3+/- individuals expressed significantly reduced levels of GATA-3, associated with markedly decreased T helper cell (Th)2 frequencies in vivo and in vitro.

A colloidal silver staining--destaining method for precise assignment of immunoreactive spots in two-dimensional protein patterns.

The characterization of protein expression patterns by two-dimensional gel electrophoresis depends on efficient and reliable identification strategies for target spots. In addition to sophisticated techniques, such as microsequencing and peptide mass spectrometry, immunodetection of membrane-immobilized proteins is a valuable method with which to identify the corresponding spots for a given set of candidate proteins. To precisely assign immunoreactive spots, this approach requires specific immunodetection and staining of total protein to be performed on the same membrane.

Treatment of two patients with Herlitz junctional epidermolysis bullosa with artificial skin bioequivalents.

Objective: To evaluate the effects of a treatment with artificial skin bioequivalents in Herlitz junctional epidermolysis bullosa (H-JEB).

Methods: Two infants, both homozygous for the Herlitz mutation R635X in the LAMB3 gene, who had refractory anemia and hypoproteinemia as a result of a continuous loss of body fluids through multiple large erosions, were treated with artificial skin bioequivalents.

Results: In the first patient, 10 of 13 acute or chronic wounds were found healed 3 to 6 weeks after the treatment, and the protein, iron, and hemoglobin levels normalized.

Restriction of de novo pyrimidine biosynthesis inhibits Th1 cell activation and promotes Th2 cell differentiation.

Leflunomide, an inhibitor of de novo pyrimidine biosynthesis, has recently been introduced as a treatment for rheumatoid arthritis in an attempt to ameliorate inflammation by inhibiting lymphocyte activation. Although the immunosuppressive ability of leflunomide has been well described in several experimental animal models, the precise effects of a limited pyrimidine supply on T cell differentiation and effector functions have not been elucidated. We investigated the impact of restricted pyrimidine biosynthesis on the activation and differentiation of CD4 T cells in vivo and in vitro.

The balance of Th1/Th2 cytokines in rheumatoid arthritis.

It has been suggested that rheumatoid inflammation is mediated by activated pro-inflammatory T helper type I cells. In contrast, immunomodulatory T helper type 2 cells and their cytokines, in particular interleukin-4, are rarely found. This chapter reviews the concept of the Th1/Th2 dichotomy and summarizes the functions of the signature cytokines of the T helper subsets.