Hypomorphic mutation in the site-1 protease Mbtps1 endows resistance to persistent viral infection in a cell-specific manner.

The prototypic arenavirus lymphocytic choriomeningitis virus (LCMV), which naturally persists in rodents, represents a model for HIV, HBV, and HCV. Cleavage of the viral glycoprotein precursor by membrane-bound transcription factor peptidase, site 1 (Mbtps1 or site-1 protease), is crucial for the life cycle of arenaviruses and therefore represents a potential target for therapy. Recently, we reported a viable hypomorphic allele of Mbtps1 (woodrat) encoding a protease with diminished enzymatic activity.

A point mutation in the amino terminus of TLR7 abolishes signaling without affecting ligand binding.

TLR7 is the mammalian receptor for ssRNA and some nucleotide-like small molecules. We have generated a mouse by N-nitrose-N'-ethyl urea mutagenesis in which threonine 68 of TLR7 was substituted with isoleucine. Cells bearing this mutant TLR7 lost the sensitivity to the small-molecule TLR7 agonist resiquimod, hence the name TLR7(rsq1).

Ernest Beutler: his life and contribution to medical science.

Ernest Beutler was one of the preeminent haematologists of the last half of the 20th and the early 21st century. In a career that spanned six decades, his research interests included such diverse areas as red cell metabolism, blood preservation, glycolipid storage diseases, leukaemias and iron metabolism. Indeed, he was quite different from most of his contemporaries in that his knowledge encompassed not only haematology and not only the medical sciences, but the biological sciences as a whole.

Impact of β2 integrin deficiency on mouse natural killer cell development and function.

Natural killer (NK) cells are innate immune cells that express members of the leukocyte β2 integrin family in humans and mice. These CD11/CD18 heterodimers play critical roles in leukocyte trafficking, immune synapse formation, and costimulation. The cell-surface expression of one of these integrins, CD11b/CD18, is also recognized as a major marker of mouse NK-cell maturation, but its function on NK cells has been largely ignored.

Rapid identification of a disease allele in mouse through whole genome sequencing and bulk segregation analysis.

In a pedigree of C57BL/6J mice homozygous for germline mutations induced by the mutagen N-ethyl-N-nitrosourea (ENU), numerous animals died under specific pathogen-free (SPF) conditions between 6 and 7 months of age. Death was caused by nephritic syndrome, which progressed to renal failure associated with focal segmental glomerulosclerosis. To identify the mutation responsible for renal disease, we sequenced genomic DNA from an affected animal using the Applied Biosystems SOLiD sequencing platform.

How host defense is encoded in the mammalian genome.

This issue of Mammalian Genome explores the genetic approach to infectious disease susceptibility as it has been applied in mammals. Although no single issue of any journal could give comprehensive treatment to a field so extensive and rapidly growing as this one, these texts describe key discoveries that provided new understanding of immune responses. Classical genetic studies opened and continue to pave the way to deep understanding of many issues in immunology.

JNK1 controls mast cell degranulation and IL-1{beta} production in inflammatory arthritis.

Rheumatoid arthritis (RA) is a chronic inflammatory disease marked by bone and cartilage destruction. Current biologic therapies are beneficial in only a portion of patients; hence small molecules targeting key pathogenic signaling cascades represent alternative therapeutic strategies. Here we show that c-Jun N-terminal kinase (JNK) 1, but not JNK2, is critical for joint swelling and destruction in a serum transfer model of arthritis.

Plant and animal sensors of conserved microbial signatures.

The last common ancestor of plants and animals may have lived 1 billion years ago. Plants and animals have occasionally exchanged genes but, for the most part, have countered selective pressures independently. Microbes (bacteria, eukaryotes, and viruses) were omnipresent threats, influencing the direction of multicellular evolution.

Slc15a4, AP-3, and Hermansky-Pudlak syndrome proteins are required for Toll-like receptor signaling in plasmacytoid dendritic cells.

Despite their low frequency, plasmacytoid dendritic cells (pDCs) produce most of the type I IFN that is detectable in the blood following viral infection. The endosomal Toll-like receptors (TLRs) TLR7 and TLR9 are required for pDCs, as well as other cell types, to sense viral nucleic acids, but the mechanism by which signaling through these shared receptors results in the prodigious production of type I IFN by pDCs is not understood. We designed a genetic screen to identify proteins required for the development and specialized function of pDCs.

MyD88 signaling in nonhematopoietic cells protects mice against induced colitis by regulating specific EGF receptor ligands.

Toll-like receptors (TLRs) trigger intestinal inflammation when the epithelial barrier is breached by physical trauma or pathogenic microbes. Although it has been shown that TLR-mediated signals are ultimately protective in models of acute intestinal inflammation [such as dextran sulfate sodium (DSS)-induced colitis], it is less clear which cells mediate protection. Here we demonstrate that TLR signaling in the nonhematopoietic compartment confers protection in acute DSS-induced colitis.

Bulk segregation mapping of mutations in closely related strains of mice.

Phenovariance may be obscured when genetic mapping is performed using highly divergent strains, and closely similar strains are preferred if adequate marker density can be established. We sequenced the C57BL/10J mouse genome using the Applied Biosystems SOLiD platform and here describe a genome-wide panel of informative markers that permits the mapping of mutations induced on the closely related C57BL/6J background by outcrossing to C57BL/10J, and backcrossing or intercrossing. The panel consists of 127 single nucleotide polymorphisms validated by capillary sequencing: 124 spaced at ∼20-Mb intervals across the 19 autosomes, and three markers on the X chromosome.

UNC93B1 mediates host resistance to infection with Toxoplasma gondii.

UNC93B1 associates with Toll-Like Receptor (TLR) 3, TLR7 and TLR9, mediating their translocation from the endoplasmic reticulum to the endolysosome, hence allowing proper activation by nucleic acid ligands. We found that the triple deficient '3d' mice, which lack functional UNC93B1, are hyper-susceptible to infection with Toxoplasma gondii. We established that while mounting a normal systemic pro-inflammatory response, i.

Antigen-specific cytotoxicity by invariant NKT cells in vivo is CD95/CD178-dependent and is correlated with antigenic potency.

Invariant NKT (iNKT) cells are a unique subset of T lymphocytes that rapidly carry out effector functions following activation with glycolipid Ags, such as the model Ag alpha-galactosylceramide. Numerous studies have investigated the mechanisms leading to Th1 and Th2 cytokine production by iNKT cells, as well as the effects of the copious amounts of cytokines these cells produce. Less is known, however, about the mechanisms of iNKT cell cytotoxicity.

I787 provides signals for c-Kit receptor internalization and functionality that control mast cell survival and development.

Mast cell (MC) differentiation, survival, and activation are controlled by the membrane tyrosine kinase c-Kit upon interaction with stem cell factor (SCF). Here we describe a single point mutation induced by N-ethyl-N-nitrosurea (ENU) mutagenesis in C57BL/6J mice-an A to T transversion at position 2388 (exon 17) of the c-Kit gene, resulting in the isoleucine 787 substitution by phenylalanine (787F), and analyze the consequences of this mutation for ligand binding, signaling, and MC development. The Kit(787F/787F) mice carrying the single amino acid exchange of c-Kit lacks both mucosal and connective tissue-type MCs.

Flt3 permits survival during infection by rendering dendritic cells competent to activate NK cells.

A previously unappreciated signal necessary for dendritic cell (DC)-mediated activation of natural killer (NK) cells during viral infection was revealed by a recessive N-ethyl-N-nitrosourea-induced mutation called warmflash (wmfl). Wmfl homozygotes displayed increased susceptibility to mouse cytomegalovirus (MCMV) infection. In response to MCMV infection in vivo, delayed NK cell activation was observed, but no intrinsic defects in NK cell activation or function were identified.

Intracellular toll-like receptors.

Foreign nucleic acids, the signature of invading viruses and certain bacteria, are sensed intracellularly. The nucleic acid-specific Toll-like receptors (TLRs) detect and signal within endolysosomal compartments, triggering the induction of cytokines essential for the innate immune response. These cytokines include proinflammatory molecules produced mainly by macrophages and conventional dendritic cells, as well as type I interferons, which are produced in great quantities by plasmacytoid dendritic cells.

An Slfn2 mutation causes lymphoid and myeloid immunodeficiency due to loss of immune cell quiescence.

Here we describe a previously unknown form of inherited immunodeficiency revealed by an N-ethyl-N-nitrosourea-induced mutation called elektra. Mice homozygous for this mutation showed enhanced susceptibility to bacterial and viral infection and diminished numbers of T cells and inflammatory monocytes that failed to proliferate after infection and died via the intrinsic apoptotic pathway in response to diverse proliferative stimuli. They also had a greater proportion of T cells poised to replicate DNA, and their T cells expressed a subset of activation markers, suggestive of a semi-activated state.

Loss of T cell and B cell quiescence precedes the onset of microbial flora-dependent wasting disease and intestinal inflammation in Gimap5-deficient mice.

Homeostatic control of the immune system involves mechanisms that ensure the self-tolerance, survival and quiescence of hematopoietic-derived cells. In this study, we demonstrate that the GTPase of immunity associated protein (Gimap)5 regulates these processes in lymphocytes and hematopoietic progenitor cells. As a consequence of a recessive N-ethyl-N-nitrosourea-induced germline mutation in the P-loop of Gimap5, lymphopenia, hepatic extramedullary hematopoiesis, weight loss, and intestinal inflammation occur in homozygous mutant mice.

Sensors of the innate immune system: their link to rheumatic diseases.

Evidence strongly suggests that excessive or protracted signaling, or both, by cell-surface or intracellular innate immune receptors is central to the pathogenesis of most autoimmune and autoinflammatory rheumatic diseases. The initiation of aberrant innate and adaptive immune responses in autoimmune diseases can be triggered by microbes and, at times, by endogenous molecules--particularly nucleic acids and related immune complexes--under sterile conditions. By contrast, most autoinflammatory syndromes are generally dependent on germline or de novo gene mutations that cause or facilitate inflammasome assembly.

A mutation of Ikbkg causes immune deficiency without impairing degradation of IkappaB alpha.

Null alleles of the gene encoding NEMO (NF-kappaB essential modulator) are lethal in hemizygous mice and men, whereas hypomorphic alleles typically cause a syndrome of immune deficiency and ectodermal dysplasia. Here we describe an allele of Ikbkg in mice that impaired Toll-like receptor signaling, lymph node formation, development of memory and regulatory T cells, and Ig production, but did not cause ectodermal dysplasia. Degradation of IkappaB alpha, which is considered a primary requirement for NEMO-mediated immune signaling, occurred normally in response to Toll-like receptor stimulation, yet ERK phosphorylation and NF-kappaB p65 nuclear translocation were severely impaired.

Study of lymphocyte subpopulations in bone marrow in a model of protein-energy malnutrition.

Objective: Protein-energy malnutrition (PEM) is an important public health problem affecting millions of people worldwide. Hematopoietic tissue requires a high nutrient supply, and a reduction in leukocytes, especially lymphocytes, suggests that some nutritional deficiencies might be altering bone marrow function and decreasing its ability to produce lymphocytes. In this study, we evaluated the effect that PEM has on lymphocyte subtypes and the cell cycle of CD5(+) cells.

The Tpl2 mutation Sluggish impairs type I IFN production and increases susceptibility to group B streptococcal disease.

Sluggish was identified in a population of third generation mice descended from N-ethyl-N-nitrosourea-mutagenized sires. Macrophages from homozygotes exhibited impaired TNF-alpha production in response to all TLR ligands tested and displayed impaired type I IFN production in response to TLR7 and TLR9 stimulations. The phenotype was confined to a critical region on mouse chromosome 18 and then ascribed to a T to A transversion in the acceptor splice site of intron 4 at position 13346 of the Map3k8 gene, resulting in defective splicing.

Viral RNA induces type I interferon-dependent cytokine release and cell death in mesangial cells via melanoma-differentiation-associated gene-5: Implications for viral infection-associated glomerulonephritis.

Viral RNA can trigger interferon signaling in dendritic cells via the innate recognition receptors melanoma-differentiation-associated gene (MDA)-5 and retinod-inducible gene (RIG)-I in the cytosol or via Toll-like receptors (TLRs) in intracellular endosomes. We hypothesized that viral RNA would also activate glomerular mesangial cells to produce type I interferon (IFN) via TLR-dependent and TLR-independent pathways. To test this hypothesis, we examined Toll/Interleukin-1 receptor domain-containing adaptor-inducing interferon-beta (TRIF)-deficient mice, which lack a key adaptor for TLR3 signaling.

Soluble CD36 ectodomain binds negatively charged diacylglycerol ligands and acts as a co-receptor for TLR2.

Background: Cluster of differentiation 36 (CD36) is a transmembrane glycoprotein involved in many biological processes, such as platelet biology, angiogenesis and in the aetiopathology of atherosclerosis and cardiovascular diseases. Toll-like receptors (TLRs) are one of the most important receptors of the innate immune system. Their main function is the recognition of conserved structure of microorganisms.