Dendritic cells (DCs) play a critical role in orchestrating the innate and adaptive components of the immune system so that appropriate, coordinated responses are mounted against infectious agents. Tissue-resident DCs interact with microbes through germline-encoded pattern-recognition receptors (PRRs), which recognize molecular patterns expressed by various microorganisms. Antigens use PRR activation to instruct DCs for the appropriate priming of natural killer (NK) cells, followed by specific T-cell responses. Due to the central role of DCs in regulating the act...

The recognition of microbial stimuli by Toll-like receptors (TLRs) expressed on dendritic cells (DCs) is essential for the regulation of immune responses. DC activation via TLRs leads to the production of proinflammatory cytokines, chemokines and surface molecules that play a key role in the regulation and control of inflammatory reactions and adaptive immunity. Minor imbalances in the feedback control of TLR-activated innate immune cells have been associated with autoimmunity in genetically prone individuals. We review here recent studies indicating how TLR-medi...

Stimulation of Toll-like receptors (TLRs) on macrophages and dendritic cells (DCs) by pathogen-derived products induces the production of cytokines, which play an important role in immune responses. Here, we investigated the role of the TPL-2 signaling pathway in TLR induction of interferon-beta (IFN-beta) and interleukin-10 (IL-10) in these cell types. It has previously been suggested that IFN-beta and IL-10 are coordinately regulated after TLR stimulation. However, in the absence of TPL-2 signaling, lipopolysaccharide (TLR4) and CpG (TLR9) stimulation resulted ...

Studies assessing the function of monocyte derived dendritic cells (MD-DC) in individuals with hepatitis C virus (HCV) infection have shown conflicting results. Impaired MD-DC function in chronic HCV infection would have important implications both for understanding the pathogenesis of HCV infection and in the use of autologous MD-DC in vaccination strategies. We determined the allostimulatory capacity of MD-DC in the same patient before and after HCV infection. Next, the phenotype, cytokine production and allostimulatory function of immature and mature MD-DC in ...

Natural killer (NK) cells are important early mediators of host immunity to viral infections. The NK activatory receptors NKG2D and NKp80, both C-type lectin-like homodimeric receptors, stimulate NK cell cytotoxicity toward target cells. Like other herpesviruses, Kaposi's sarcoma-associated herpesvirus (KSHV) down-regulates MHC class I molecules to avoid detection by cytotoxic T lymphocytes but renders cells susceptible to NK cell cytotoxicity. We now show that the KSHV immune evasion gene, K5, reduces cell surface expression of the NKG2D ligands MHC class I-rela...

The glycolipid alpha-galactosylceramide (alpha-GalCer) is a potent activator of invariant natural killer T (iNKT) cells and has been shown to be an effective agent against cancer, infections and autoimmune diseases. The effectiveness of alpha-GalCer and its alkyl chain analogues depends on efficient loading and presentation by the antigen-presenting molecule CD1d. To monitor the ability of CD1d to present the glycolipids, we have used a phage display strategy to generate recombinant antibodies with T cell receptor-like (TCRL) specificity against the human CD1d (h...

Erratum in: Eur J Immunol. 2008 May;38(5):1465-6. MHC-peptide-specific Fab antibodies binding to HLA-A*0201 complexes presenting the wild-type EAAGIGILTV (EAA) or analogue Melan-A 10-mer ELAGIGILTV (ELA) peptide were generated to study efficacy of peptide processing and presentation. None of the selected Fab antibodies detected the naturally processed EAA/HLA-A*0201 complex on melanoma tumor cells, confirming the known low peptide number on the cell surface. To study the effect of peptide presentation and processing in more detail, genes coding for the A27L-mu...

Invariant NKT cells (iNKT cells) recognize CD1d/glycolipid complexes. We demonstrate that the nonglycosidic compound threitolceramide efficiently activates iNKT cells, resulting in dendritic cell (DC) maturation and the priming of Ag-specific T and B cells. Threitolceramide-pulsed DCs are more resistant to iNKT cell-dependent lysis than alpha-galactosylceramide-pulsed DCs due to the weaker affinity of the human iNKT TCR for CD1d/ threitolceramide than CD1d/alpha-galactosylceramide complexes. iNKT cells stimulated with threitolceramide also recover more quickly fr...

The CD1 family of antigen-presenting molecules consists of five members, CD1a to e. Of these molecules CD1d has been the subject of much interest over the past 10 years following the discovery that this molecule presents antigens to a group of T cells known as invariant natural killer T cells (iNKT). iNKT cells carry an invariant T cell receptor which contains homologous gene segments in mouse and man. iNKT cells are positively selected in the thymus in the same manner as major histocompatibility complex restricted T cells, except iNKT cells require CD1d to be pr...

Highly regulated activation of B cells is required for the production of specific antibodies necessary to provide protection from pathogen infection. This process is initiated by specific recognition of antigen through the B cell receptor (BCR), leading to early intracellular signaling followed by the late recruitment of T cell help. In this study we demonstrate that specific BCR uptake of CD1d-restricted antigens represents an effective means of enhancing invariant natural killer T (iNKT)-dependent B cell responses in vivo. This mechanism is effective over a wid...

Over the past ten years, investigators have shown that T lymphocytes can recognize not only peptides in the context of MHC class I and class II molecules but also foreign and self-lipids in association with the nonclassical MHC class I molecules the CD1 proteins. We describe the events that have led to the discovery of the role of CD1 molecules, their pattern of intracellular trafficking, and their ability to sample different intracellular compartments for self- and foreign lipids. Structural and functional aspects of lipid presentation by CD1 molecules are prese...

The glycosphingolipids globotrihexosylceramide (Gb3, CD77) and isoglobotrihexosylceramide (iGb3) are isomers differing only in one glycosidic bond and have been implicated in several processes of the innate and adaptive immune system. AIMS: 1) To verify the function of Gb3 in the pathogenesis of hemolytic-uremic syndrome as the cellular receptor responsible for cytotoxicity caused by verotoxin (VT) elaborated by Shigella and certain strains of E.coli. 2) To investigate in vivo the previously implicated function of iGb3 as the endogenous lipid ligand responsible f...

Infection with influenza A virus (IAV) presents a substantial threat to public health worldwide, with young, elderly, and immunodeficient individuals being particularly susceptible. Inflammatory responses play an important role in the fatal outcome of IAV infection, but the mechanism remains unclear. We demonstrate here that the absence of invariant NKT (iNKT) cells in mice during IAV infection resulted in the expansion of myeloid-derived suppressor cells (MDSCs), which suppressed IAV-specific immune responses through the expression of both arginase and NOS, resu...

To optimize vaccination strategies, it is important to use protocols that can 'jump-start' immune responses by harnessing cells of the innate immune system to assist the expansion of antigen-specific B and T cells. In this Review, we discuss the evidence indicating that invariant natural killer T (iNKT) cells can positively modulate dendritic cells and B cells, and that their pharmacological activation in the presence of antigenic proteins can enhance antigen-specific B- and T-cell responses. In addition, we describe structural and kinetic analyses that assist in...

Regulated mRNA decay is a highly important process for the tight control of gene expression. Inherently unstable mRNAs contain AU-rich elements (AREs) in the 3' untranslated regions that direct rapid mRNA decay by interaction with decay-promoting ARE-binding proteins (ARE-BPs). The decay of ARE-containing mRNAs is regulated by signaling pathways that are believed to directly target ARE-BPs. Here, we show that BRF1 involved in ARE-mediated mRNA decay (AMD) is phosphorylated by MAPK-activated protein kinase 2 (MK2). In vitro kinase assays using different BRF1 fragm...

Stable isotope labeling by amino acids in cell culture (SILAC) has become a versatile tool for quantitative, mass spectrometry (MS)-based proteomics. Here, we completely label mice with a diet containing either the natural or the (13)C(6)-substituted version of lysine. Mice were labeled over four generations with the heavy diet, and development, growth, and behavior were not affected. MS analysis of incorporation levels allowed for the determination of incorporation rates of proteins from blood cells and organs. The F2 generation was completely labeled in all org...

The MAPU 2.0 database contains proteomes of organelles, tissues and cell types measured by mass spectrometry (MS)-based proteomics. In contrast to other databases it is meant to contain a limited number of experiments and only those with very high-resolution and -accuracy data. MAPU 2.0 displays the proteomes of organelles, tissues and body fluids or conversely displays the occurrence of proteins of interest in all these proteomes. The new release addresses MS-specific problems including ambiguous peptide-to-protein assignments and it provides insight into genera...

Mass spectrometry is a powerful technology for the analysis of large numbers of endogenous proteins. However, the analytical challenges associated with comprehensive identification and relative quantification of cellular proteomes have so far appeared to be insurmountable. Here, using advances in computational proteomics, instrument performance and sample preparation strategies, we compare protein levels of essentially all endogenous proteins in haploid yeast cells to their diploid counterparts. Our analysis spans more than four orders of magnitude in protein abu...