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Results for “Innate Immunity Recognition”

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At least 127 records · Page 7Linked to original sources
PubMed2005

Regulation of acquired immunity by gamma delta T-cell/dendritic-cell interactions.

In humans, innate immune recognition of mycobacteria, including Mycobacterium tuberculosis and Mycobacterium leprae, involves toll-like receptor-2 (TLR-2), expressed on immature dendritic cells (DCs), and the T-cell gammadelta receptor expressed by a subpopulation of T cells that utilize Vdelta2 (Vdelta2 T cells). To investigate modulatory relationships between these host-cell populations in a microbial context, in vitro experiments were performed with human DCs and Vdelta2 T cells stimulated with model TLR-2 ligands and phosphoantigens, respectively. We observed that TLR-2-stimulated DCs enhanced interferon-gamma (IFN-gamma) production by Vdelta2 T cells; conversely, activated Vdelta2 T cells enhanced TLR-2-induced DC maturation via soluble factors including IFN-gamma, which costimulated interleukin-12 (IL-12) p70 secretion by DCs. Exposure of DCs to activated Vdelta2 T cells was critical for Th1 T-cell priming when TLR-2 stimulation was limiting. These results suggest that Vdelta2 T cells may play an adjuvant role in priming protective antimycobacterial immunity when TLR-2 stimulation is lacking, as may occur if the infectious inoculum is small, or if the pathogen is an intrinsically weak activator of DCs.

Adult↗
PubMedDate not supplied

A biologically important single nucleotide polymorphism within the toll-like receptor-4 gene is not associated with rheumatoid arthritis.

BACKGROUND: Rheumatoid arthritis (RA) is a heterogeneous condition affecting 1-2% of the population. Genetics account for 30% of disease susceptibility, with one third arising from the Major Histocompatibility Complex. The toll-like receptor 4 (TLR-4) gene which has been mapped to chromosome 9 (9q32-q33) is involved in innate immune recognition with subsequent proinflammatory cytokine release including TNF. A single nucleotide polymorphism (+896A-->G) resulting in the amino acid substitution (Asp299Gly) has been shown to interrupt TLR-4 mediated signalling. OBJECTIVE: We sought to determine if this TLR-4 polymorphism influences susceptibility to rheumatoid arthritis. METHODS: DNA was extracted from 879 healthy controls and 212 rheumatoid arthritis patients recruited from the north of England. Genotyping was performed using a 5' nuclease Taqman allelic discrimination assay. Allele frequencies were compared between the two groups. We also examined whether an association existed in non-carriers of the DRB1 shared epitope alleles. RESULTS: The frequency of the rare allele was 5.9% in the controls and 7% in the patients. Comparison of rare allele carriage between controls and patients revealed no significant difference p = 0.13. This was also the case in shared epitope negative individuals p = 0.92. CONCLUSION: The TLR-4 +896 polymorphism does not appear to influence susceptibility to rheumatoid arthritis.

Adult↗
PubMed2006

Recognition of cytosolic DNA activates an IRF3-dependent innate immune response.

Nucleic acid recognition upon viral infection triggers type I interferon production. Viral RNA is detected by both endosomal, TLR-dependent and cytosolic, RIG-I/MDA5-dependent pathways. TLR9 is the only known sensor of foreign DNA; it is unknown whether innate immune recognition of DNA exists in the cytosol. Here we present evidence that cytosolic DNA activates a potent type I interferon response to the invasive bacterium Listeria monocytogenes. The noninvasive Legionella pneumophila triggers an identical response through its type IV secretion system. Activation of type I interferons by cytosolic DNA is TLR independent and requires IRF3 but occurs without detectable activation of NF-kappaB and MAP kinases. Microarray analyses reveal a unique but overlapping gene-expression program activated by cytosolic DNA compared to TLR9- and RIG-I/MDA5-dependent responses. These findings define an innate immune response to DNA linked to type I interferon production.

Animals↗
PubMed2005

The Mycobacterium tuberculosis cell wall component mycolic acid elicits pathogen-associated host innate immune responses.

Recognition of conserved pathogen-associated molecular patterns constitutes a crucial step in the initiation of innate immune responses. We studied the contribution to the host-pathogen interaction of mycolic acid (MA), a major lipid component of the cell envelope of the macrophage intracellular pathogen Mycobacterium tuberculosis and other mycobacteria. MA administered to the peritoneal cavity or to the airways induced a unique macrophage morphotype, similar to the foamy macrophage derivatives observed in tuberculous granulomas and characterized by intracellular accumulation of neutral lipids and entry into mitosis. When assayed for production of inflammatory mediators, a conditioning rather than a direct activation of the MA-elicited foamy macrophages was observed. MA enabled production of IFN-gamma and myeloperoxidase, enhanced TNF-alpha production and suppressed IL-10 upon renewed exposure to innate triggers. Intratracheal instillation of MA mimicked additional features of the airway response to M. tuberculosis infection, namely a rapid but transient neutrophil influx and IL-6 production and a chronic IL-12 production. These MA-elicited cellular innate defenses and the accompanying formation of foamy macrophages identify for the first time the foamy macrophage morphotype as part of the host response to a pathogen-associated structure. Furthermore, these results characterize MA as a direct trigger of innate immunity, distinct from Toll-like receptor ligands.

Animals↗
PubMed2006

Recognition of pathogens and activation of immune responses in Drosophila and horseshoe crab innate immunity.

In innate immunity, pattern recognition receptors discriminate between self- and infectious non-self-matter. Mammalian homologs of the Drosophila Toll protein, which are collectively referred to as Toll-like receptors (TLRs), recognize pathogen-associated molecular patterns (PAMPs), including lipopolysaccharides (LPS) and lipoproteins, whereas the Drosophila Toll protein does not act as a PAMP receptor, but rather binds to Spätzle, an endogenous peptide. In Drosophila, innate immune surveillance is mediated by members of the peptidoglycan recognition protein (PGRP) family, which recognize diverse bacteria-derived peptidoglycans and initiate appropriate immune reactions including the release of antimicrobial peptides and the activation of the prophenoloxidase cascade, the latter effecting localized wound healing, melanization, and microbial phagocytosis. In the horseshoe crab, LPS induces hemocyte exocytotic degranulation, resulting in the secretion of various defense molecules, such as coagulation factors, antimicrobial peptides, and lectins. Recent studies have demonstrated that the zymogen form of the serine protease factor C, a major granular component of hemocyte, also exists on the hemocyte surface and functions as a biosensor for LPS. The proteolytic activity of activated factor C initiates hemocyte exocytosis via a G protein mediated signal transduction pathway. Furthermore, it has become clear that an endogenous mechanism for the feedback amplification of the innate immune response exists and is dependent upon a granular component of the horseshoe crab hemocyte.

Animals↗
PubMed2026

LitCTL1: A novel C-type lectin involved in the mucosal and cellular immunity of the common periwinkle Littorinalittorea.

C-type lectins (CTLs) are vital pattern-recognition receptors (PRRs) that mediate innate immune responses in mollusks, yet their characterization in Caenogastropoda, the largest gastropod group, remains limited. This study characterizes LitCTL1, a novel secreted single-domain C-type lectin from the common periwinkle, Littorina littorea. The 199-amino acid polypeptide contains a conserved carbohydrate recognition domain with canonical QPD and WND motifs and is predicted to form a homodimer. Uniquely, LitCTL1 was localized in both circulating hemocytes and mucus-secreting epithelial cells of the foot, mantle, and hypobranchial gland - the first report of such dual localization for a molluscan lectin, linking systemic and mucosal defense. Expression analysis revealed that LitCTL1 is constitutively expressed in hemocytes. Functional assays with recombinant LitCTL1 demonstrated its role as a potent opsonin with hemagglutinating activity, significantly enhancing hemocyte spreading and the phagocytosis of zymosan. Genomic analysis reveals that LitCTL1 belongs to a rapidly diversifying, genus-specific expansion distinct from conserved perlucin-like lineages. These results identify LitCTL1 as a key effector molecule in both systemic and mucosal innate immunity, likely reflecting an evolutionary adaptation to the microbial challenges of the intertidal environment.

Animals↗
PubMed2000

Molecular mechanisms of target recognition in an innate immune system: interactions among factor H, C3b, and target in the alternative pathway of human complement.

In the alternative pathway of complement (APC) factor H is the primary control factor involved in discrimination between potential pathogens. The APC deposits C3b on possible Ags, and the interaction with factor H determines whether the initial C3b activates the APC. Factor H is composed of a linear array of 20 homologous short consensus repeats (SCR) domains with many functional sites. Three of these sites are involved in binding C3b and regulating complement activation; others bind to sialic acid and/or heparin and are responsible for host recognition. Using site-directed mutations we have examined the contributions of each of these sites to target discrimination and to functional activities of factor H. Decay acceleration by SCR1-4 of C3/C5 convertases bound to nonactivators was strongly dependent on SCR domains 11-15 and 16-20. Loss of these regions caused a 97% loss of activity, with SCR16-20 being the most critical (>90% loss). On APC activators the pattern of site usage was different and unique on each. On yeast, deletion of the 10 C-terminal domains (SCR11-20) had no effect on specific activity. On rabbit erythrocytes, this deletion caused loss of 75% of the specific activity. An examination of binding affinity to C3b on the four cell types demonstrated that factor H exhibits a unique pattern of SCR involvement on each cell. The results reveal a complex molecular mechanism of discrimination between microbes and host in this ancient innate defense system and help explain the different rates and intensities of APC activation on different biological particles.

Animals↗
PubMed2003

Pattern recognition molecules and innate immunity to parasites.

Recent pioneering advances in understanding how plants, insects and worms eliminate pathogens has led to the realization that innate immunity plays a vital role in protecting humans from infection. This comprehensive review examines the molecules involved in innate immune responses, how they act to control parasites and if their engagement can explain many immune features characteristic of parasitic infections.

Animals↗
PubMed2000

Carbohydrate-mediated recognition systems in innate immunity.

There is growing interest in carbohydrate-recognizing receptors of the innate immune system. Among them are members of the C-type lectin family, which include the collectins and the selectins and which operate by ligating exogenous (microbial) or endogenous carbohydrates. De novo assignments of the sequences of ligands for carbohydrate-recognizing receptors are among the most challenging topics in cell biology. This is because of the heterogeneity of oligosaccharides on proteins and lipids, and their availability only in limited amounts. To address the need for a microprocedure for direct binding studies with oligosaccharides derived from glycoproteins, we introduced the neoglycolipid technology for generating solid phase oligosaccharide probes for binding experiments. The technology has enabled assignments of unsuspected oligosaccharide ligands for the selectins and given valuable insights into those for the collectins. The ligands so far identified appear not to be unique for a given receptor system; there are considerable cross-reactions. Specificity can be created, however, through different modes of oligosaccharide presentation on macromolecular carriers, or the expression of a particular oligosaccharide sequence on a selected cell type in a given body compartment, and the regulated expression of the receptor protein at the desired location. The existence of unique ligand structures is not ruled out, however. Co-ligation of a receptor may also occur to a second carbohydrate or even to a non-carbohydrate ligand to create a unique assembly. A further group of C-type lectin-like proteins occurs on natural killer (NK) cells and NK T cells, and is associated with activation or inhibition of the cell effector functions. An important challenge is to determine whether carbohydrates are among physiological ligands for this important group of receptors.

Animals↗
PubMed2002

Distinct response of human B cell subpopulations in recognition of an innate immune signal, CpG DNA.

Innate immunity has recently gained renewed interest in its ability to regulate adaptive immunity. Among the innate immune signals, CpG DNA has revealed its potential as a vaccine adjuvant. However, the cellular mechanism for the effect of CpG DNA on the humoral immune response is not well understood. Here, we investigated the effects of CpG DNA on human B cell differentiation using highly purified B cell subsets: naive, germinal center (GC), and memory B cells. In the in vitro culture system that mimics the primary or secondary immune response in vivo, CpG DNA markedly augmented the proliferation and generation of plasma cells from naive and memory B cells. CpG DNA dramatically increased plasma cell generation from GC B cells. However, CpG DNA did not have effect on memory B cell generation from GC B cells. These results suggest that CpG DNA potentiates the B cell adaptive immune response by enhancing terminal differentiation, but does not affect the generation of memory B cells.

Adjuvants, Immunologic↗
PubMed2002

A novel fucose recognition fold involved in innate immunity.

Anguilla anguilla agglutinin (AAA), a fucolectin found in the serum of European eel, participates in the recognition of bacterial liposaccharides by the animal innate immunity system. Because AAA specifically recognizes fucosylated terminals of H and Lewis (a) blood groups, it has been used extensively as a reagent in blood typing and histochemistry. AAA contains a newly discovered carbohydrate recognition domain present in proteins of organisms ranging from bacteria to vertebrates. The crystal structure of the complex of AAA with alpha-L-fucose characterizes the novel fold of this entire lectin family, identifying the residues that provide the structural determinants of oligosaccharide specificity. Modification of these residues explains how the different isoforms in serum can provide a diverse pathogen-specific recognition.

Agglutinins↗
PubMed2006

Therapeutic targeting of pattern-recognition receptors.

Innate immune system could recognize the pathogen-associated molecular patterns by pattern-recognition receptors like Toll-like receptor (TLR) and nucleotide-binding oligomerisation domain (NOD) protein. Information regarding the structure and signalling pathways of TLRs and NODs could provide opportunities for new therapeutic approaches to modulate the innate immunity. Therapeutic targeting could be done by prevention of ligand binding to leucine-rich repeats domains of receptors, blocking the interactions between receptors (like Toll/interleukin-1 receptor domains of TLRs) and adaptors in signalling pathways, blocking the enzymes in signalling pathways, and immunostimulation with vaccine adjuvants. These therapeutic approaches could be useful in the treatment of different human diseases like immunological disorders, infections, and cancers. Further research on these receptors and their signalling pathways could help scientists to identify new candidates for therapeutic targeting.

Adjuvants, Immunologic↗
PubMed2003

Suppression of allergic reaction by lambda-carrageenan: toll-like receptor 4/MyD88-dependent and -independent modulation of immunity.

BACKGROUND: Recognition of foreign substances by innate immunity through pattern recognition receptors (PRRs) regulates acquired immunity such as allergic reaction. Because PRRs recognize heterogeneous ligands, daily food intake can potentially regulate immune allergic reaction. OBJECTIVE: Elucidation of the effect of lambda-carrageenan on allergic reactions was aimed. METHOD: IFN-gamma and IL-4 was measured in in vitro T cell-stimulated culture. Cytokine production from macrophages in response to lambda-carrageenan was measured as indicator for innate immunity activation. Mice were immunized with OVA in alum to induce specific IgE, and then histamine release was induced by systemic injection of OVA. RESULTS: Activation of innate immunity by lambda-carrageenan is dependent on Toll-like receptor-4 (TLR4) and MyD88, in which induction of pro-inflammatory cytokines such as TNF-alpha and IL-6 was largely impaired in macrophages from TLR4- and MyD88-deficient mice. Footpad oedema, a model for in vivo inflammatory reactions, was significantly reduced in these mice. Similar to recent evidence showing a preference for the stimulation of Th1 via TLR/MyD88 signalling, lambda-carrageenan showed enhanced IFN-gamma and decreased IL-4 in stimulated T cell cultures. Interestingly, increased IFN-gamma production was still seen in TLR4- and MyD88-deficient splenocytes. Oral administration of lambda-carrageenan to immunized mice successfully decreased OVA-specific IgE, and lambda-carrageenan was also effective in previously immunized mice. Further, serum histamine release upon systemic challenge of OVA was significantly inhibited. Neither OVA-specific IgG1/IgG2a nor cytokine secretion from in vitro cultures were altered, suggesting the involvement of multiple PRRs as demonstrated by TLR4/MyD88-independent IFN-gamma up-regulation. The simultaneous feeding of OVA with lipopolysaccharide abrogated oral tolerance, but lambda-carrageenan was not only devoid of such an effect but was also found to promote oral tolerance in the absence of TLR4. CONCLUSION: lambda-Carrageenan was suggested to be a useful dietary supplement to ameliorate allergic reactions while maintaining oral tolerance-dependent intestinal homeostasis.

Adaptor Proteins, Signal Transducing↗
PubMed2026

miRNA-mediated control of TLR-NLR interplay in the uterus: A hidden corner of recurrent pregnancy loss.

Toll-like receptors (TLRs) and NOD-like receptors (NLRs) are crucial pattern recognition receptors that initiate inflammatory responses and immunological activation upon detecting pathogen- or damage-associated molecular patterns (PAMPs/DAMPS) in the female reproductive tract, thereby maintaining homeostasis and supporting pregnancy success. Their signaling pathways play a significant role in reproductive disorders by mediating the immune response to various pathogenic stimuli. Recurrent pregnancy loss (RPL), defined as the natural ending of two or more pregnancies before 24 weeks of gestation, approximately half of these patients remain idiopathic without precise prognostic, diagnostic, and therapeutic plans. Emerging data point that microRNAs are essential for immunological control in the female reproductive tract. MicroRNAs (miRNAs) are non-coding RNAs that regulate gene expression by binding to mRNA and preventing translation into protein. miRNAs play a role in many biological processes, including the development and differentiation of trophoblasts, the activation and implantation of embryos, immune tolerance, and the receptivity of the endometrium during implantation. Given their capacity to regulate up to 30 % of the human genome, miRNAs offer a promising avenue for understanding the immunopathogenesis of pregnancy complications. Recent research has detected differential expression of specific miRNAs in reproductive system pathologies. This review focuses on microRNAs and their association with idiopathic recurrent miscarriage, a condition characterized by considerable heterogeneity. Future studies identifying the precise mechanisms linking miRNA-mediated immune dysregulation in RPL immunopathogenesis could open the way for novel personalized therapeutic and diagnostic strategies.

Female↗
PubMed2025

Repeats mimic pathogen-associated patterns across a vast evolutionary landscape.

An emerging hallmark of many human diseases is transcription of typically silenced repetitive DNA containing pathogen-associated molecular patterns (PAMPs). These PAMPs engage the innate immune system via pattern recognition receptors (PRRs)-a phenomenon known as viral mimicry. We propose a statistical physics framework to quantify viral mimicry by measuring "selective forces" that enrich PAMPs compared to a genome-wide reference distribution. We validate our predictions by identifying repeats that bind different PRRs and show potential viral mimics in different repeat families across eukaryotic genomes, suggesting shared mechanisms drive emergence and retention. We propose two non-exclusive evolutionary hypotheses. The first "repeat-centric" hypothesis posits PAMPs are integral to the repeat life cycle and are therefore enriched as they mediate repeat expansion. The second "organism-centric" hypothesis proposes viral mimicry functions as a cell-intrinsic feedback mechanism for sensing and reacting to transcriptional dysregulation, which provides a selective pressure to maintain PAMPs in genomes.

Humans↗