Function Of Innate Immune System Research Articles

Toll-like Receptor

Toll like receptor (TLR), one of the key functions of innate immune system, can recognize not only exogenous pathogen-associated molecular patterns, namely PAMPs, but also endogenous molecules created upon tissue injury, sterile inflammation and degeneration. Endogenous TLR ligands are called as damage-associated molecular patters (DAMPs), including endogenous molecules released by activated and necrotic cells, and extracellular matrix molecules. DAMPs are also known as alarmins. TLR research has brought about new insights in the rheumatic diseases. Previous reports suggest that TLRs and the signal pathways intensively contribute to the pathogenesis of rheumatoid arthritis (RA) and other arthritic conditions with interaction of various TLR ligands. Accumulated knowledge of TLR system is summarized to overlook TLRs and the signaling pathway in arthritis conditions, with special reference to RA.

Defining a longitudinal survival model to examine forced treadmill running as a countermeasure for diet-induced weight gain

Diet-induced weight gain increases disease risk via disruption of the innate immune system. Flow cytometry is commonly used to assess the immune system; however, in mice such measurements traditionally require terminal procedures and tissue collection to generate sufficient sample. The present study refined an existing flow cytometry method to reduce the number of mice needed to longitudinally measure monocytes. CD-1 male mice were randomly assigned to one of the three groups: DS (diet-induced weight gain + sedentary), DE (diet-induced weight gain + forced treadmill running [total distance 35,755 ± 1832 m]) or NS (normal weight gain + sedentary). DS and DE consumed a 60% fat diet and NS consumed a 10% fat diet ad libitum. Saphenous vein blood samples were collected weekly for a period of six weeks and three-colour flow cytometry was used to measure changes in monocyte (CD11b(+)/14(+)) concentration and cell-surface toll-like receptor 4 (TLR4) expression. DS (18%) and DE (17%) gained more weight than NS (P < 0.001). On a group basis, DS expressed 17% more TLR4 than DE and NS (P = 0.005). The present study demonstrates that a longitudinal survival model can be used to reduce the number of animals needed to complete flow cytometry experiments. Exercise during diet-induced weight prevented some (decreased monocyte TLR4 expression) but not all aspects of innate immune system function.

The older brain, inflammation, vaccination and the prevention of dementia

SummaryAn important protective function of the brain's innate immune system is to detect the presence of proteins such as amyloid and to remove them before they become neurotoxic, as is thought to occur in Alzheimer's disease (AD). Ageing affects the immune system response to infection and can influence the systemic response to vaccination and other potential immunotherapeutic agents. The generation of systemic antibodies is a vital component of the immune response, facilitating the identification and clearance of pathogens from the central nervous system (CNS). Experimental evidence using transgenic animal models of AD has shown successful clearance of amyloid from the CNS following vaccination with an amyloid peptide, and consequently a trial of amyloid beta peptide (Aβ) vaccination was undertaken in older people with AD. This produced some unexpected results, as not only was there evidence for amyloid plaque removal, but also a small number of cases developed encephalitis. A detailed review of the response to vaccination and the neuropathology findings are discussed, showing that the findings are understandable given the effects of ageing upon the innate immune system in the brain. Finally, the therapeutic potential of manipulating the regulatory components of the ageing innate immune system in order to inhibit brain inflammation and reduce cognitive decline is outlined.

Recognizing the First Responders

![Figure][1] CREDIT: C. BICKEL/ SCIENCE 2009 marked the 20th anniversary of Charles Janeway's seminal hypothesis that the body's response to infection is mediated by receptors on immune cells that recognize microbial patterns. Before this, immunologists primarily studied T and B lymphocytes, which express highly specific antigen receptors, but Janeway's prediction that direct microbial detection by immune cells other than lymphocytes precedes and is required for subsequent lymphocyte activation helped open the door to a new field of immunology: the study of the innate immune system. Much work over the past 20 years has borne out Janeway's predictions, and the fundamental importance of the innate immune system is now well established. The collection of articles in this issue encompasses both the primary focus of the field over the past two decades—the molecular dissection of microbial recognition—and also more recent areas of interest, including the interaction between the innate and adaptive immune systems and the identification of noninfectious diseases associated with innate immune system function. A Perspective by Rehwinkel and Reis e Sousa (p. [284][2]) discusses recent advances in the elucidation of how members of the RIG-I–like receptor family distinguish viral nucleic acids from the abundance of host nucleic acids present in an infected cell. The ability to specifically recognize viral nucleic acids is critical for proper immune responses to viral infection. Another family of microbial receptors, the NLRs, is discussed in a Review by Ting and colleagues (p. [286][3]). These receptors have received a great deal of recent attention because of their role in the inflammatory protein complex termed the inflammasome; however, as Ting et al. present, mounting evidence indicates that their inflammasome-independent functions may play an equally important role in the responses to pathogens by the innate immune system. How microbial recognition by the innate immune system couples to the activation of T and B lymphocytes of the adaptive immune system is discussed in a Review by Iwasaki and Medzhitov (p. [291][4]). This Review highlights the fact that we still have much to learn about this cooperation, particularly in cases when the microbes are being sensed within the cell. Although it is well recognized that the innate immune system is critical for responses to microbial insults, research has also emerged demonstrating that the innate immune system may play an unexpected role in diseases not classically associated with the immune system. A Review by Schroder and colleagues (p. [296][5]) explores one example: the role of the innate immune receptor NLRP3 in the metabolic diseases type 2 diabetes and gout. A collection of articles at Science Signaling ([www.sciencemag.org/special/immunity][6]) highlights immune responses to pathogens, the mechanism of interleukin-1 signaling, and aspects of the control of the adaptive immune response by dendritic cells. Together, these articles highlight how far our understanding of the innate immune system has come in the past 20 years and suggest areas where the important discoveries of the next decades are likely to come. [1]: pending:yes [2]: /lookup/doi/10.1126/science.1185068 [3]: /lookup/volpage/327/286?iss=5963 [4]: /lookup/volpage/327/291 [5]: /lookup/volpage/327/296?iss=5963 [6]: http://www.sciencemag.org/special/immunity

T-bet-Deficient NOD Mice Are Protected from Diabetes Due to Defects in Both T Cell and Innate Immune System Function

The transcription factor T-bet (Tbx21) is critical for Th1 polarization of CD4(+) T cells. Genetic deletion of Tbx21 can cause either exacerbation or attenuation of different autoimmune diseases in animal models. In the nonobese diabetic (NOD) mouse, genetic deletion of the Ifng or the Il12b (IL-12p40) genes, which are both critical Th1 cytokines, does not reduce the incidence of autoimmune diabetes. These results suggest that autoimmune diabetes in the NOD may not be a Th1-driven disease. However, we report that Tbx21 deficiency in the NOD mouse completely blocks insulitis and diabetes due to defects both in the initiation of the anti-islet immune response and in the function of CD4(+) effector T cells. We find defective priming of naive islet-reactive T cells by the innate immune system in Tbx21(-/-) animals. By contrast to naive cells, activated islet-reactive BDC2.5 TCR-transgenic T cells do not require Tbx21 in recipient animals for efficient adoptive transfer of diabetes. However, when these BDC2.5 TCR-transgenic effector cells lack Tbx21, they are less effective at entering the pancreas and promoting diabetes than Tbx21(+/+) cells. Tbx21(-/-) regulatory T cells function normally in vitro and diabetes can be restored in Tbx21(-/-) mice by reducing regulatory T cell numbers. Thus, the absence of diabetes in the NOD.Tbx21(-/-) is due to intrinsic defects in both T cells and cells of the innate immune system paired with the relative preservation of regulatory T cell function.

Roosting ecology and variation in adaptive and innate immune system function in the Brazilian free-tailed bat (Tadarida brasiliensis)

Bats have recently been implicated as reservoirs of important emerging diseases. However, few studies have examined immune responses in bats, and even fewer have evaluated these responses in an ecological context. We examined aspects of both innate and adaptive immune response in adult female Brazilian free-tailed bats (Tadarida brasiliensis) at four maternity roosts (two natural caves and two human-made bridges) in south-central Texas. Immune measurements included in vitro bactericidal ability of whole blood and in vivo T cell mediated response to mitogenic challenge. Bactericidal activity in T. brasiliensis varied with roosting ecology, but appears to be sensitive to colony-level effects. Blood from females living at one cave had significantly lower bactericidal ability than blood from females at three other sites. T cell mediated response in this species was associated with variation in roost ecology, with females from two caves having greater responses than females from two bridges. T cell mediated response and bactericidal activity were negatively correlated with one another within individuals that were tested for both. Variation in immunological response of T. brasiliensis is important for understanding the influence of the environment on the frequency and distribution of immunologically competent individuals and for understanding disease-host dynamics in this and other colonial species.

Developmental and epigenetic regulation of the human TLR3 gene

The receptor encoded by the human TLR3 gene recognizes double-strand RNAs (dsRNAs) associated with viral infection. TLR3 expression is strongly activated upon differentiation of monocytes to dendritic cells, and can be further stimulated by the dsRNA analog polyinosine:polycytosine (PI:C). We report evidence for developmental regulation of the TLR3 gene. In dendritic cells derived from cord blood, both differentiation- and PI:C-associated TLR3 transcriptional activation are impaired as compared to cells from adults. Consistent with relative expression patterns, chromatin states and remodeling differ between newborn and adult samples. TLR3 expression in newborn dendritic cells exhibits heterocellularity and allelic imbalance (skewing), features characteristic of cis-acting epigenetic control. These findings reveal a new source for variability in innate immune system function and provide a model for further study of perinatal epigenetic transitions during development.

Injury Enhances Resistance to Escherichia coli Infection by Boosting Innate Immune System Function

Major injury is widely thought to predispose the injured host to opportunistic infections. This idea is supported by animal studies showing that major injury causes reduced resistance to polymicrobial sepsis induced by cecal ligation and puncture. Although cecal ligation and puncture represents a clinically relevant sepsis model, we wanted to test whether injury might also lead to greater susceptibility to peritoneal infection caused by a single common pathogen, Escherichia coli. Contrary to our expectation, we show herein that the LD(50) for sham-injured mice was 10(3) CFU of E. coli, whereas the LD(50) for burn-injured mice was 50 x 10(3) CFU at 7 days postinjury. This injury-associated enhanced resistance was apparent as early as 1 day after injury, and maximal resistance was observed at days 7 and 14. We found that burn-injured mice had higher numbers of circulating neutrophils and monocytes than did sham mice before infection and that injured mice were able to recruit greater numbers of neutrophils to the site of infection. Moreover, the peritoneal neutrophils in burn-injured mice were more highly activated than neutrophils from sham mice as determined by Mac-1 expression, superoxide generation, and bactericidal activity. Our findings suggest that the enhanced innate immune response that develops following injury, although it is commonly accepted as the mediator of the detrimental systemic inflammatory response syndrome, may also, in some cases, benefit the injured host by boosting innate immune antimicrobial defenses.

The Immunological Dilemma: Cellular Innate and Adaptive Immune Response Versus Human Acute Myeloid Leukemia

It is generally accepted that acute myelogenous leukemia (AML) patients are immunocompromized. On the other hand, antileukemic immune reactivity is important for the improved survival of AML patients treated with alloge- neic stem cell transplantation and antileukemic immunotherapy is also considered for patients treated with conventional chemotherapy. In this article, we review the available studies of disease- and therapy- induced immune dysfunctions in AML patients, including the function of the cellular innate and adaptive immune system of AML patients (i) with newly diagnosed disease before treatment, (ii) immunological functions of AML patients with severe therapy induced cytopenia before hematopoietic reconstitution; and (iii) the immune reconstitution following the initial period of hematopoietic re- constitution after autologous and allogeneic stem cell transplantation. A more detailed knowledge about the immune sys- tems of these patients is essential for an optimal design of future clinical immunotherapy studies in AML.

Select Plant Tannins Induce IL-2Rα Up-Regulation and Augment Cell Division in γδ T Cells

Gammadelta T cells are innate immune cells that participate in host responses against many pathogens and cancers. Recently, phosphoantigen-based drugs, capable of expanding gammadelta T cells in vivo, entered clinical trials with the goal of enhancing innate immune system functions. Potential shortcomings of these drugs include the induction of nonresponsiveness upon repeated use and the expansion of only the Vdelta2 subset of human gammadelta T cells. Vdelta1 T cells, the major tissue subset, are unaffected by phosphoantigen agonists. Using FACS-based assays, we screened primary bovine cells for novel gammadelta T cell agonists with activities not encompassed by the current treatments in an effort to realize the full therapeutic potential of gammadelta T cells. We identified gammadelta T cell agonists derived from the condensed tannin fractions of Uncaria tomentosa (Cat's Claw) and Malus domestica (apple). Based on superior potency, the apple extract was selected for detailed analyses on human cells. The apple extract was a potent agonist for both human Vdelta1 and Vdelta2 T cells and NK cells. Additionally, the extract greatly enhanced phosphoantigen-induced gammadelta T cell expansion. Our analyses suggest that a tannin-based drug may complement the phosphoantigen-based drugs, thereby enhancing the therapeutic potential of gammadelta T cells.

Assessment of exercise-induced alterations in neutrophil function in horses

To evaluate the effects of a standardized exercise test to exhaustion in horses on leukocyte function ex vivo. 6 Thoroughbred geldings. Blood samples were obtained from each horse before exercise; at exhaustion (termed failure); and at 2, 6, 24, 48, and 72 hours after exercise to evaluate hematologic changes, rate of leukocyte apoptosis, and leukocyte production of reactive oxygen species (ROS) ex vivo. To assess leukocyte function, leukocyte ROS production in response to stimulation with lipopolysaccharide, peptidoglycan, zymosan, and phorbol myristate acetate was evaluated. Apoptosis was evaluated via assessment of caspase activity in leukocyte lysates. In response to lipopolysaccharide, production of ROS by leukocytes was significantly increased at 2 hours and remained increased (albeit not significantly) at 6 hours after exercise, compared with the preexercise value. In the absence of any stimulus, leukocyte ROS production was significantly increased at 6 and 24 hours after exercise. In contrast, ROS production in response to phorbol myristate acetate was significantly decreased at 6, 24, and 72 hours after exercise. Leukocyte ROS production induced by zymosan or peptidoglycan was not altered by exercise. Leukocytosis was evident for 24 hours after exercise, and neutrophilia was detected during the first 6 hours. A significant increase in the rate of leukocyte apoptosis was detected at failure and 72 hours after exercise. Results indicated that strenuous exercise undertaken by horses causes alterations in innate immune system functions, some of which persist for as long as 72 hours after exercise.

Modulation of Neutrophil Function by Hormones

Endocrine regulation of the neutrophilic component of innate immunity with a particular focus on the production of reactive oxygen species (ROS) is the subject of this review. Endocrine hormones contribute to neutrophil mediated pathology in several ways either by directly activating the cells, as is the case with an angiotensin activation of NADPH oxidase on neutrophils and monocytes to contribute to atherosclerosis, or by having biphasic effects depending upon the stage of systemic inflammation, i.e. in a hyper-inflammatory phase or a hypo-inflammatory or anergic state, as seen with growth hormone. Some factors, such as a novel anti-inflammatory peptide from salivary glands, the tripeptide FEG, and hypothalamic proline-rich peptide have more subtle effects and appear to negatively regulate the priming events required for neutrophil activation. Investigations on the impact and role of endocrine hormones on neutrophil function and ROS production have contributed to the understanding of the efficacy of some medications in treating inflammation, as is the case with the angiotensin receptor blockers, and should lead to the development of novel drugs that modulate innate immune system function and the severity of an inflammatory response. Keywords: Hormones, peptides, reactive oxygen species, superoxide, leukocytes, anti-inflammatory

Allergic Airway Inflammation Inhibits Pulmonary Antibacterial Host Defense

The innate immune system of the lung is a multicomponent host defense system and in addition has an instructing role in regulating the quality and quantity of the adaptive immune response. When the interaction between innate and adaptive immunity is disturbed, pathological conditions such as asthma can develop. It was the aim of the study to investigate the effect of the allergic inflammation of the lung on the innate host defense during bacterial infection. Human bronchial epithelial cells were preincubated with Th2 cytokines and infected with Pseudomonas aeruginosa. The effect of the Th2 cytokines on the mRNA levels of antimicrobial peptides and the antimicrobial activity of HBEC was determined. To investigate the influence of an allergic inflammation on pulmonary host defense in vivo, mice sensitized and challenged with OVA were infected with P. aeruginosa, and the number of viable bacteria in the lungs was determined together with markers of inflammation like cytokines and antimicrobial peptides. Exposure of airway epithelial cells to Th2 cytokines resulted in a significantly decreased antimicrobial activity of the cells and in suppressed mRNA levels of the antimicrobial peptide human beta-defensin 2. Furthermore, mice with allergic airway inflammation had significantly more viable bacteria in their lungs after infection. This was consistent with reduced levels of proinflammatory cytokines and of the antimicrobial peptide cathelin-related antimicrobial peptide. These results show that an allergic airway inflammation suppresses the innate antimicrobial host defense. The adaptive immune system modulates the functions of the pulmonary innate immune system.

Efficient Ex vivo Expansion of Vα24+ NKT Cells Derived From G-CSF-mobilized Blood Cells

Natural killer T (NKT) cells are involved in the function of innate immune systems and also play an important role in regulating acquired immune responses. In previous reports, we showed that Valpha24+ NKT cells proliferated more efficiently from granulocyte-colony stimulating factor (G-CSF)-mobilized peripheral blood mononuclear cells (PBMC) than from non-mobilized PBMC. However, the mechanism of this enhanced NKT cell expansion is not yet clear. The goal of this research was to develop culture conditions for the more efficient ex vivo expansion of NKT cells. G-CSF-mobilized PBMC was cultured in AIM-V medium supplemented with 10% auto-plasma, 100 ng/mL alpha-galactosylceramide (alpha-GalCer) and 100 IU/mL recombinant human (rh) interleukin (IL)-2. The efficiency of the expansion of Valpha24+ NKT cells was evaluated on day 12. The expansion-fold of Valpha24+ NKT cells was augmented depending on the proportion of CD14+ cells at the beginning of culture. The depletion of Valpha24+ NKT cells abrogated the expansion of Valpha24+ NKT cells. Depletion of CD56+ NK cells from mobilized PBMC enhanced, and add-back of purified CD56+ NK cells suppressed the expansion of Valpha24+ NKT cells. Experiments with different timings for the addition of cells, IL-2 and alpha-GalCer suggested that follow-up supplementation with IL-2 or CD14+ cells should be avoided for the efficient expansion of Valpha24+ NKT cells. These results should be useful for the development of an efficient and practical expansion protocol for adoptive immunotherapy with Valpha24+ NKT cells.

Human intrahepatic biliary epithelial cells function in innate immunity by producing IL‐6 and IL‐8 via the TLR4‐NF‐κB and ‐MAPK signaling pathways

Human intrahepatic biliary epithelial cells (HIBECs) may play active roles in both the innate and adaptive immune responses. Little is known, however, about the role of toll-like receptors (TLRs) on HIBECs in inflammatory cholangiopathies. The expression of TLR1-9 and the biological responses to their ligands, lipopolysaccharide (LPS) or lipoteichoic acid (LTA), were studied in cultured HIBECs by reverse transcription-polymerase chain reaction, immunoblotting, and enzyme-linked immunosorbent assay. HIBECs constitutively expressed transcripts encoding TLR1-6 and 9, as well as myeloid differentiation factor 88 (MyD88), MD2, and CD14. Stimulation of HIBECs with LPS resulted in translocation of NF-kappaB subunits from the cytoplasmic to the nuclear fraction, followed by increased secretion of a variety of chemokines/cytokines, including interleukin-8 (IL-8), monocyte chemotactic protein-1 (MCP-1), and IL-6. Treatment with BAY11-7082 efficiently inhibited the LPS-induced transcription and secretion of these chemokines/cytokines. In HIBECs, the mitogen-activated protein kinases (MAPKs) were also activated by LPS stimulation. These results indicated that LPS activates HIBECs via a TLR4-MyD88-dependent pathway. Stimulation of HIBECs with LTA induced the secretion of a similar profile of cytokines/chemokines via a TLR2-MyD88-dependent pathway. In HIBECs, at least TLR2 and 4 are capable of mediating innate immune system function in vitro. This result, in conjunction with our recent finding that TLR4 expression is increased in biliary epithelial cells in primary biliary cirrhosis, suggests the involvement of TLRs in the development of chronic inflammatory cholangiopathies.

Enhanced innate immune system function following severe injury increases resistance to intraperitoneal E. coli infection and improves survival

Enhanced innate immune system function following severe injury increases resistance to intraperitoneal E. coli infection and improves survival

Acid exposure is an immune disruptor in adult Rana pipiens

Acidic environments are physiological stressors for amphibians. The objective of the present study was to document the effect of an acidic environment on innate immune system function under controlled experimental conditions in Rana pipiens. We developed an in vivo assay, by injecting a suspension of 1-microm fluorescent beads in fluid thioglycollate, to induce peritonitis. The number of peritoneal exudate leukocytes and their phagocytic activity did not increase with thioglycollate injection when frogs were exposed to pH 5.5 compared to when frogs were exposed to pH 7.0. An environment of pH 5.5 disrupted the inflammatory response of frogs compared to an environment of pH 7.0; at pH 5.5, more nonphagocytic leukocytes and fewer highly phagocytic leukocytes were found compared to those in frogs exposed to pH 7.0. Frogs stimulated by thioglycollate injection and exposed to pH 5.5 had a 50% increase in cells that did not exhibit phagocytosis and a 4- to 10-fold reduction in the number of highly phagocytic cells. This is evidence that acid exposure functions as an immune disruptor in adult R. pipiens under laboratory conditions.

Prolonged suppression of the innate immune system in the horse following an 80 km endurance race.

An increased susceptibility to bacterial and viral infections of the respiratory tract, which results in a loss of performance, has been reported in racehorses. Much research has focused on the influence of high-intensity exercise of a short duration on immune system function in horses, but scant attention has been given to prolonged endurance exercise as an immune modulator. The objective of this study was to evaluate the effect of an 80 km endurance race on the monocyte and neutrophil oxidative burst, serum cortisol, glutamine and plasma glucose concentrations in 8 endurance-trained horses (mean +/- s.d. age 9.4 +/- 2.2 years). Blood samples were drawn from the horses prior to and following an 80 km ride. Mean time for completion of the 80 km race was 306 +/- 40 mins. Immediately post race mean serum cortisol concentration, blood monocyte and neutrophil counts were higher and blood lymphocyte counts and plasma glucose concentration were lower compared with prerace values (P < 0.05). Neutrophil and monocyte oxidative burst activity decreased following the race and had not regained prerace values after 3 days of rest (P < 0.05). The present study indicates that long duration exercise in horses has a negative impact on the function of the innate immune system that lasts several days post race. Precise mechanisms instigating the fall in innate immune system function are unclear and multifactorial, but may be attributed, at least in part, to a high serum cortisol response during very prolonged exercise. A prolonged bout of exercise results in a long-term suppression of the innate immune system function in horses which may, in part, account for the observed increase of infectious episodes in horses during training.

Multiple pathways to allograft rejection.

Allograft rejection results from a complex process involving both the innate and acquired immune systems. The innate immune system predominates in the early phase of the allogeneic response, during which chemokines and cell adhesion play essential roles, not only for leukocyte migration into the graft but also for facilitating dendritic and T-cell trafficking between lymph nodes and the transplant. This results in a specific and acquired alloimmune response mediated by T cells. Subsequently, T cells and cells from innate immune system function synergistically to reject the allograft through nonexclusive pathways, including contact-dependent T cell cytotoxicity, granulocyte activation by either Th1 or Th2 derived cytokines, NK cell activation, alloantibody production, and complement activation. Blockade of individual pathways generally does not prevent allograft rejection, and long-term allograft survival is achieved only after simultaneous blockade of several of them. In this review, we explore each of these pathways and discuss the experimental evidence highlighting their roles in allograft rejection.