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At least 19 recordsLinked to original sources
PubMed2003

TRAF6, a molecular bridge spanning adaptive immunity, innate immunity and osteoimmunology.

Tumor necrosis factor (TNF) receptor associated factor 6 (TRAF6) is a crucial signaling molecule regulating a diverse array of physiological processes, including adaptive immunity, innate immunity, bone metabolism and the development of several tissues including lymph nodes, mammary glands, skin and the central nervous system. It is a member of a group of six closely related TRAF proteins, which serve as adapter molecules, coupling the TNF receptor (TNFR) superfamily to intracellular signaling events. Among the TRAF proteins, TRAF6 is unique in that, in addition to mediating TNFR family signaling, it is also essential for signaling downstream of an unrelated family of receptors, the interleukin-1 (IL-1) receptor/Toll-like receptor (IL-1R/TLR) superfamily. Gene targeting experiments have identified several indispensable physiological functions of TRAF6, and structural and biochemical studies have revealed the potential mechanisms of its action. By virtue of its many signaling roles, TRAF6 represents an important target in the regulation of many disease processes, including immunity, inflammation and osteoporosis.

Animals↗
PubMed2004

On the origins of adaptive immunity: innate immune receptors join the tale.

Among members of the Ig superfamily (IgSF), antigen receptors have the unique capacity to rearrange their variable domains, thereby creating an extensive repertoire for antigen recognition. It is assumed that antigen receptors evolved from a non-rearranging IgSF member by insertion of a transposable element. Although the nature of this predecessor is unknown, two multigene families of innate immune receptors that bear a close structural resemblance to antigen receptor chains have been identified in mammals and bony fish, respectively: signal-regulatory proteins (SIRPs) and novel immune-type receptors (NITRs). Members of both families encode V-set Ig domains with a typical antigen receptor-like joining (J) motif and possess the potential to signal through immunoreceptor tyrosine-based inhibition motifs (ITIMs) or immunoreceptor tyrosine-based activation motifs (ITAMs). By analogy to the T-cell receptor (TCR) and certain innate receptors [e.g. killer cell inhibitory receptors (KIRs)] that recognize MHC molecules, SIRP members regulate immune function by interaction with broadly expressed 'self' ligands. We propose the existence of an evolutionary and functional link between innate and adaptive immune receptors that sheds light on the nature of the antigen receptor predecessor(s).

Amino Acid Sequence↗
PubMed2004

Immunomodulation by Dok Din Daeng (Aeginetia indica Roxb.) extracts in female B6C3F1 mice: II. Humoral immunity, innate immunity and hematology.

In the previous report, we have provided evidence that Aeginetia indica Roxbert (DDD) extracts enhance T cell-mediated immune responses. The study reported here was focused on the hematological and immunological effects, including B cells, natural killer (NK) cells, macrophages and neutrophils, of the whole plant extract using water (WDDD) or ethanol (EDDD) as the solvent. The extracts were administered to female B6C3F1 mice by gavage for WDDD (10-100%) and intraperitoneally for EDDD (0.25-250 mg/kg) for 28 days. In addition to hematological evaluation, several quantitative measures and functional assays (e.g., the splenic phenotypic analysis, IgM antibody-forming cell responses, natural killer cell activity, mononuclear phagocyte system [MPS] and neutrophil activity) were employed to examine the effects of DDD extracts on the innate and humoral immunities. The results from this study demonstrated that exposure to WDDD and EDDD produced minimal changes in the activities of B cells and natural killer cells, macrophages and neutrophils. Overall, hematological parameters were not affected by exposure to WDDD or EDDD. Taken together, the enhancing effect of DDD extracts on T cells may be primarily responsible for the successful and long-time use of this traditional herbal medicine in Thailand.

Administration, Oral↗
PubMed2002

Toll-like receptor 9, CpG DNA and innate immunity.

Innate immunity provides the first line of defense against invading pathogens and is essential for survival in the absence of adaptive immune responses. Innate immune recognition relies on a limited number of germ-line encoded receptors, such as Toll-like receptors (TLRs), that evolved to recognize conserved molecular patterns of microbial origin. To date, ten transmembrane proteins in the TLR family have been described. It is becoming increasingly clear that bacterial CpG DNA and synthetic oligodeoxynucleotides (ODN) containing unmethylated CpG are potent inducers of the innate immune system including dendritic cells (DCs), macrophages, and natural killer (NK) and NKT cells. Recent studies indicate that mucosal or systemic delivery of CpG DNA can act as a potent adjuvant in a vaccine combination or act alone as an anti-microbial agent. Recently, it was shown that TLR9 is essential for the recognition of unmethylated CpG DNA since cells from TLR9-deficient mice are unresponsive to CpG stimulation. Although the effects of CpG DNA on bone marrow-derived cells are beginning to unfold, there has been little or no information regarding the mechanisms of CpG DNA function on non-immune cells or tissues. This review focuses on the recent advances in CpG-DNA/TLR9 signaling effects on the activation of innate immunity.

Animals↗
PubMed2006

Effects of kefir fractions on innate immunity.

Innate immunity that protects against pathogens in the tissues and circulation is the first line of defense in the immune reaction, where macrophages have a critical role in directing the fate of the infection. We recently demonstrated that kefir modulates the immune response in mice, increasing the number of IgA+ cells in the intestinal and bronchial mucosa and the phagocytic activity of peritoneal and pulmonary macrophages. The aim of this study was to further characterize the immunomodulating capacity of the two fractions of kefir (F1: solids including bacteria and F2: liquid supernatant), by studying the cytokines produced by cells from the innate immune system: peritoneal macrophages and the adherent cells from Peyer's patches. BALB/c mice were fed either kefir solid fraction (F1) or kefir supernatant (F2) for 2, 5 or 7 consecutive days. The number of cytokine (IL-1alpha, IFNgamma, TNFalpha, IL-6 and IL-10) producing cells was determined on peritoneal macrophages and adherent cells from Peyer's patches. Both kefir fractions (F1 and F2) induced similar cytokine profiles on peritoneal macrophages (only TNFalpha and IL-6 were up-regulated). All cytokines studied on adherent cells from Peyer's patches were enhanced after F1 and F2 feeding, except for IFNgamma after F2 administration. Moreover, the percentage of IL-10+cells induced by fraction F2 on adherent cells from Peyer's patches was significantly higher than the one induced by fraction F1. Different components of kefir have an in vivo role as oral biotherapeutic substances capable of stimulating immune cells of the innate immune system, to down-regulate the Th2 immune phenotype or to promote cell-mediated immune responses against tumours and also against intracellular pathogenic infections.

Animals↗
PubMed2002

Alternative splicing of transcripts encoding Toll-like plant resistance proteins - what's the functional relevance to innate immunity?

Innate immunity in plants and animals shares many structural and functional homologies, which suggests an ancient origin of cellular defense mechanisms in both kingdoms. Pathogen sensing in animal innate immunity is mediated by Toll-like receptors (TLRs). These receptors have TIR (Toll/interleukin-1 receptor) domains and leucine-rich repeats, which are modules also present in many plant resistance (R) proteins. Molecular analysis of transcripts encoding animal TLRs and Toll-like plant R proteins revealed many cases of alternative splicing. Recent studies of the tobacco N and the Arabidopsis RPS4 genes, both encoding Toll-like plant R proteins, showed that intron-deprived genes have reduced or no activity, suggesting that alternative splicing is a crucial component in these signaling pathways.

Alternative Splicing↗
PubMed2001

Toll receptors in innate immunity.

Innate immunity is the first-line host defense of multicellular organisms that rapidly operates to limit infection upon exposure to infectious agents. In addition, the cells and molecules operating during this early stage of the immune response in vertebrates have a decisive impact on the shaping of the subsequent adaptive response. Genetic studies initially performed in the fruitfly Drosophila and later in mice have revealed the importance of proteins of the Toll family in the innate immune response. We present here our current understanding of the role of this evolutionary ancient family of proteins that are thought to function as cytokine receptors (Toll in Drosophila) or pattern-recognition receptors (TLRs in mammals) and activate similar, albeit non-identical, signal-transduction pathways in flies and mammals.

Amino Acid Sequence↗
PubMed2005

Human peptidoglycan recognition protein S is an effector of neutrophil-mediated innate immunity.

Innate immune responses to bacteria require cooperative interactions between host recognition molecules and phagocytes. The peptidoglycan recognition proteins (PGRPs) are a large group of proteins found in insects and mammals that bind to bacterial peptidoglycan (PGN). PGRP-S is located with other antimicrobial proteins, such as lysozyme, in the granules of human neutrophils. Whereas both PGRP-S and lysozyme recognize PGN, the exact binding specificity of human PGRP-S, its functional activity, and its potential synergy with other neutrophil-derived bactericidal proteins such as lysozyme have not been determined. Here we show that human PGRP-S binds to and inhibits the growth of Staphylococcus aureus (containing lysine-type PGN) and Escherichia coli (containing mesodiaminopimelic acid-type PGN). The binding affinity and thus antimicrobial activity of PGRP-S is determined by the third amino acid in the PGN stem peptide. Furthermore, the antimicrobial effect of PGRP-S against E coli is synergistic with lysozyme, and lysozyme and PGRP-S colocalize in neutrophil extracellular traps (NETs), suggesting that these granule-derived proteins act together to kill bacteria trapped in the NETs. Taken together, these results indicate that human PGRP-S plays a role in innate immunity in the context of neutrophils by contributing to the killing of intracellular and extracellular bacteria.

Anti-Infective Agents↗
PubMed2004

Nods and 'intracellular' innate immunity.

Innate immunity relies on the detection of microbial invaders by two distinct systems. One system comprises a family of membrane-bound receptors, termed the Toll-like receptors, while the other family, termed the nucleotide-binding site/leucine-rich repeat (NBS/LRR) proteins, consists of molecules that are found in the cytoplasmic compartment. These two detection systems recognize conserved molecular components of microbes including such structural motifs as lipopolysaccharide from the Gram-negative bacterial cell wall and peptidoglycan (PGN) found in the cell wall of both Gram-negative and Gram-positive bacteria. This review focuses on two members of the NBS/LRR family of proteins, Nod1 and Nod2. Recently, the microbial motifs sensed by these two molecules have been characterized. Both Nod1 and Nod2 recognize PGN, however, each requires distinct molecular motifs to attain sensing. Nod1 recognizes a naturally occurring muropeptide of PGN that presents a unique amino acid at its terminus called diaminopilemic acid (DAP). This amino acid is found mainly in the PGN of Gram-negative bacteria designating Nodl as a sensor of Gram-negative bacteria. In contrast, Nod2 can detect the minimal bioactive fragment of PGN, called muramyl dipeptide. Thus Nod2 is a general sensor of bacterial PGN. Since mutations in the gene encoding Nod2 were recently shown to be associated with the chronic inflammatory disease, Crohn's disease, these results are discussed in the context of how disrupting the interplay between host detection and bacterial aggression may lead to inflammatory diseases.

Adaptor Proteins, Signal Transducing↗
PubMed1999

The Toll-receptor family and control of innate immunity.

Innate immune recognition is mediated by a system of germline-encoded receptors that recognize conserved molecular patterns that are associated with microbial pathogens. These receptors are coupled to signal transduction pathways that control expression of a variety of inducible immune-response genes. Toll receptors and the associated signaling pathways of nuclear factor kappaB may represent the most ancient host defense system found in mammals, insects and plants.

Animals↗
PubMed2005

[Mechanisms of innate immunity].

Innate (natural) immunity differs from acquired immunity with respect to the detection systems (receptors and structures detected on pathogens), the cells engaged, and the nature of the mechanisms. Innate immunity is an ancient system, with similar structures in plants, invertebrates, and vertebrates are involved in the development of defense against pathogens. Toll-like receptor (TLR) structures are present in all organisms, and some mechanisms (i.e. complement activation) were also discovered in invertebrates and vertebrates. During infection, innate reactions develop before acquired immune reactions do. Natural immunity involves such reactions as the production of different cytokines, chemokines, and interleukins; the innate, cytokines-dependent nonspecific immunity of leukocytes; HLA-independent pathogen-killing cells, and phagocytosis. Such cytokines as interferons, the TNF family, and interleukines 12 and 18 participate in antiviral, antibacterial, antiprotozoan and anticancer natural immunity. NK cells, cytokines of the TNF family, and the complement system activated by lectins are engaged in the non-specific killing of infected or tumor cells. As over-activation of the innate system can be dangerous, the system must be submitted the strict control. The exact mechanism of this control system is not yet known, but there are several indications of its presence.

Animals↗
PubMed2006

[New aspect of immune system: innate immunity and acquired immunity].

Recently, it has been turned out that our internal defense system is composed of two distinct components; innate/natural immune system and acquired/adaptive immune system. The former innate immunity is principally located at the surface area such as skin and mucosal compartment, while the latter acquired immunity is observed mainly in the circulating blood and lymphoid organs. The critical difference between those two systems exists in the receptors as well as their ligands. Rearranged gene-derived receptors like immunoglobulin (Ig) and MHC molecule-restricted alphabeta-type of T-cell receptors (TCR) with high specificities and memories are used to recognize peptide antigens in the acquired immunity, whereas non-rearranged invaliant receptors such as toll-like receptors (TLR), gammasigmaTCR and CD1 molecule-restricted alphabeta TCR are employed to detect lipid/glycolipid or nucleic acid-related antigens in the innate immunity. Based on such new findings, the actual roles of immunity are discussed.

Animals↗
PubMed2006

Regulatory T cells and innate immune regulation in tumor immunity.

Innate and adaptive immunity play important roles in immunosurveillance and tumor destruction. However, increasing evidence suggests that tumor-infiltrating immune cells may have a dual function: inhibiting or promoting tumor growth and progression. Although regulatory T (Treg) cells induce immune tolerance by suppressing host immune responses against self- or nonself-antigens, thus playing critical roles in preventing autoimmune diseases, they might inhibit antitumor immunity and promote tumor growth. Recent studies demonstrate that elevated proportions of Treg cells are present in various types of cancers and suppress antitumor immunity. Furthermore, tumor-specific Treg cells can inhibit immune responses only when they are exposed to antigens presented by tumor cells. Therefore, Treg cells at tumor sites have detrimental effects on immunotherapy directed to cancer. This review will discuss recent progress in innate immunity, Treg cells, and their regulation through Toll-like receptor (TLR) signaling. It was generally thought that TLR-mediated recognition of specific structures of invading pathogens initiate innate and adaptive immune responses through dendritic cells. New evidence suggests that TLR signaling may directly regulate the suppressive function of Treg cells. Linking TLR signaling to the functional control of Treg cells opens intriguing opportunities to manipulate TLR signaling to control both innate and adaptive immunity against cancer.

Animals↗
PubMed2005

Early life immune challenge alters innate immune responses to lipopolysaccharide: implications for host defense as adults.

Fever is the most common manifestation of the innate immune response to invading pathogens. Animals prevented from developing fever have increased morbidity and mortality to infection. We now show that early life events can program this innate immune response, in that rats that have been challenged neonatally with the immune stimulant lipopolysaccharide (LPS) have both suppressed febrile responses to LPS as adults and significantly reduced nuclear factor (NF)-kappaB activation in peripheral immune organs. This was associated with reduced levels of proinflammatory cytokines tumor necrosis factor (TNF)-alpha, and interleukin-6 (IL-6) in the plasma after adult LPS challenge, compared with animals that have received saline neonatally. In contrast, adult LPS challenge elicited higher corticosterone levels in the animals that had been treated neonatally with LPS. When this increased corticosterone response was negated by adrenalectomy or by administration of the glucocorticoid receptor antagonist RU-486, both the cytokine and febrile responses were normalized. This study indicates that the innate immune response can be programmed by a neonatal LPS challenge, whereby an amplified hypothalamic-pituitary-adrenal response causes reduced cytokine synthesis and an attenuated febrile response to an adult immune challenge. In light of the importance of fever in the host defense response, these alterations may have deleterious consequences on an individual's ability to combat disease later in life.

Adrenalectomy↗
PubMed2003

[Antiinfective host defense mechanism: toll-like receptors and innate immunity].

The innate immune system has evolved as the first line of defense against invading microorganisms. The recent discovery of the toll-like receptors(TLRs) has rapidly expanded our knowledge of molecular events that initiate host-pathogen interactions. The TLRs, which are expressed on the surface of cells, involved in innate immune recognition, including macrophages and dendritic cells, have a crucial role in the detection of microbial infection. Signals initiated by the interaction of TLRs with pathogen-associated molecular patterns (PAMPs) induce activation of the inflammatory and antimicrobial innate immune response. Ten members of the TLR family have been identified, and they appear to recognize PAMPs, including lipopolysaccharide, peptidoglycan, and bacterial DNA. There has been considerable interest in how adaptive immune responses are controlled by the innate immune system. Recent studies have suggested that TLRs may control the induction of Th1 responses and that a separate system of recognition regulates the Th2 response. Thus TLR signaling represents a key component in the innate immune response to microbial infection.

Animals↗
PubMed2001

Roles of Toll-like receptors in innate immune responses.

Innate immunity recognizes invading micro-organisms and triggers a host defence response. However, the molecular mechanism for innate immune recognition was unclear. Recently, a family of Toll-like receptors (TLRs) was identified, and crucial roles for these receptors in the recognition of microbial components have been elucidated. The TLR family consists of 10 members and will be expanding. Each TLR distinguishes between specific patterns of microbial components to provoke innate immune responses. The activation of innate immunity then leads to the development of antigen-specific adaptive immunity. Thus, TLRs control both innate and adaptive immune responses.

Adaptor Proteins, Signal Transducing↗
PubMed1997

Dependence of the adaptive immune response on innate immunity: some questions answered but new paradoxes emerge.

Recently a new model of vertebrate immunity has been gaining popularity. In this new model it is hypothesized that activation of innate immunity is a prerequisite for an adaptive immune response to an antigen. Following activation the innate system induces key costimulator molecules on APC, which are essential for antigen-driven clonal expansion of T and B cells. The model largely explains the need for adjuvants in the induction of adaptive immunity, provides a possible mechanism for the immune system to perceive the biological nature of a pathogen and thereby produce the most effective immune response, and transfers much of the onus of self-non-self discrimination from the adaptive to the innate immune system. In the present article we highlight two paradoxes raised by the new model. First, by linking adaptive immunity to innate recognition the immune system is unable to take full advantage of the genetic diversity of T and B cell antigen receptors. Thus, the ability of the immune system to combat a pathogen is totally dependent on the efficiency of recognition by the innate system and, therefore, the germ-line mutation rate of the genes involved in the innate response. Second, if signals from the innate system induce costimulatory molecules on APC, then one would expect the accidental clonal expansion of many autoreactive T and B cells. We suggest that one means of resolving the first paradox is to propose that the major reason for the evolution of adaptive immunity was to provide, via immunological memory, resistance to reinfection, rather than simply to combat the primary infection by the pathogen. In the case of autoreactivity we suggest that autodestruction is prevented by immune responses being tightly regulated at the effector T cell level. Finally, we argue that the two paradoxes, rather than undermining the new model of immunity, highlight our lack of understanding of key elements of the vertebrate immune system.

Adaptation, Physiological↗