Recognition Of Pathogen-associated Molecular Patterns Research Articles

Guanosine-specific single-stranded ribonuclease effectors of a phytopathogenic fungus potentiate host immune responses.

Plants activate immunity upon recognition of pathogen-associated molecular patterns. Although phytopathogens have evolved a set of effector proteins to counteract plant immunity, some effectors are perceived by hosts and induce immune responses. Here, we show that two secreted ribonuclease effectors, SRN1 and SRN2, encoded in a phytopathogenic fungus, Colletotrichum orbiculare, induce cell death in a signal peptide- and catalytic residue-dependent manner, when transiently expressed in Nicotiana benthamiana. The pervasive presence of SRN genes across Colletotrichum species suggested the conserved roles. Using a transient gene expression system in cucumber (Cucumis sativus), an original host of C. orbiculare, we show that SRN1 and SRN2 potentiate host pattern-triggered immunity responses. Consistent with this, C. orbiculare SRN1 and SRN2 deletion mutants exhibited increased virulence on the host. In vitro analysis revealed that SRN1 specifically cleaves single-stranded RNAs at guanosine, leaving a 3'-end phosphate. Importantly, the potentiation of C. sativus responses by SRN1 and SRN2, present in the apoplast, depends on ribonuclease catalytic residues. We propose that the pathogen-derived apoplastic guanosine-specific single-stranded endoribonucleases lead to immunity potentiation in plants.

Evolution of the Major Components of Innate Immunity in Animals.

Innate immunity is present in all animals. In this review, we explore the main conserved mechanisms of recognition and innate immune responses among animals. In this sense, we discuss the receptors, critical for binding to pathogen-associated molecular patterns (PAMPs) or danger-associated molecular patterns (DAMPs); the downstream signaling proteins; and transcription factors that govern immune responses. We also highlight conserved inflammatory mediators that are induced after the recognition of DAMPs and PAMPs. At last, we discuss the mechanisms that are involved in the regulation and/or generation of reactive oxygen species (ROS), influencing immune responses, like heme-oxygenases (HOs).

Comparative transcriptome analysis of hepatopancreas reveals the potential mechanism of shrimp resistant to Vibrio parahaemolyticus infection

Vibrio parahaemolyticus carrying a pathogenic plasmid (VPAHPND) is one of the main causative agents of acute hepatopancreatic necrosis disease (AHPND) in shrimp aquaculture. Knowledge about the mechanism of shrimp resistant to VPAHPND is very helpful for developing efficient strategy for breeding AHPND resistant shrimp. In order to learn the mechanism of shrimp resistant to AHPND, comparative transcriptome was applied to analyze the different expressions of genes in the hepatopancreas of shrimp from different families with different resistance to VPAHPND. Through comparative analysis on the hepatopancreas of shrimp from VPAHPND resistant family and susceptible family, we found that differentially expressed genes (DEGs) were mainly involved in immune and metabolic processes. Most of the immune-related genes among DEGs were highly expressed in the hepatopancreas of shrimp from resistant family, involved in recognition of pathogen-associated molecular patterns, phagocytosis and elimination of pathogens, maintenance of reactive oxygen species homeostasis and other immune processes etc. However, most metabolic-related genes were highly expressed in the hepatopancreas of shrimp from susceptible family, involved in metabolism of lipid, vitamin, cofactors, glucose, carbohydrate and serine. Interestingly, when we analyzed the expression of above DEGs in the shrimp after VPAHPND infection, we found that the most of identified immune-related genes remained at high expression levels in the hepatopancreas of shrimp from the VPAHPND resistant family, and most of the identified metabolic-related genes were still at high expression levels in the hepatopancreas of shrimp from the VPAHPND susceptible family. The data suggested that the differential expression of these immune-related and metabolic-related genes in hepatopancreas might contribute to the resistance variations of shrimp to VPAHPND. These results provided valuable information for understanding the resistant mechanism of shrimp to VPAHPND.

Sensing and signaling in periodontal inflammation via toll like receptors: A review

Periodontal disease is a chronic inflammatory condition that affects the supporting structures of teeth, including the gingiva, periodontal ligament, and alveolar bone. Toll-like receptors (TLRs) play a crucial role in the recognition of pathogen-associated molecular patterns (PAMPs) from bacteria that cause periodontal disease. TLR activation triggers an inflammatory response that aims to eliminate the bacteria and repair damaged tissue. However, if the inflammation persists, it can lead to further tissue destruction and bone loss. This review discusses the mechanisms of TLRs in periodontal disease progression, including the recognition of bacteria, activation of immune cells, tissue destruction, and inhibition of immune response. Strategies for down-regulating TLRs, such as small-molecule inhibitors, antibodies, natural products, micro RNA, and nutritional interventions, are also discussed. Targeting TLRs is a promising therapeutic approach for reducing chronic inflammation associated with periodontal disease. Further research is needed to develop safe and effective strategies for down-regulating TLRs in humans.

PCAP-1a, an exopolysaccharide from Pectobacterium actinidiae, exerts the dual role of immunogenicity and virulence in plants

Plant defense mechanisms begin with the recognition of microbe-associated molecular patterns or pathogen-associated molecular patterns (MAMPs/PAMPs). Several carbohydrates, such as chitin, were reported to induce plant defenses, acting as elicitors. Regrettably, the structures of polysaccharide elicitors have rarely been characterized, and their recognition receptors in plants remain unknown. In the present study, PCAP-1a, an exopolysaccharide (PCAP-1a) purified from Pectobacterium actinidiae, was characterized and found to induce rapid cell death of dicotyledons, acting as a polysaccharide elicitor to induce plant immunity. A series of pattern-triggered immunity (PTI) responses were triggered, including reactive oxygen species production, phosphorylation of mitogen-activated protein kinases and gene transcriptional reprogramming. Moreover, we confirmed that CERK1 is probably one of the immune coreceptors for plants to recognize PCAP-1a. Notably, PCAP-1a also promotes the infection caused by P. actinidiae. In conclusion, our study supports the potential of PCAP-1a as a toxin that plays a dual role of virulence and immune induction in pathogen-plant interactions.

Inflammatory ER stress responses dictate the immunopathogenic progression of systemic candidiasis.

Recognition of pathogen-associated molecular patterns can trigger the inositol-requiring enzyme 1 α (IRE1α) arm of the endoplasmic reticulum (ER) stress response in innate immune cells. This process maintains ER homeostasis and also coordinates diverse immunomodulatory programs during bacterial and viral infections. However, the role of innate IRE1α signaling in response to fungal pathogens remains elusive. Here, we report that systemic infection with the human opportunistic fungal pathogen Candida albicans induced proinflammatory IRE1α hyperactivation in myeloid cells that led to fatal kidney immunopathology. Mechanistically, simultaneous activation of the TLR/IL-1R adaptor protein MyD88 and the C-type lectin receptor dectin-1 by C. albicans induced NADPH oxidase-driven generation of ROS, which caused ER stress and IRE1α-dependent overexpression of key inflammatory mediators such as IL-1β, IL-6, chemokine (C-C motif) ligand 5 (CCL5), prostaglandin E2 (PGE2), and TNF-α. Selective ablation of IRE1α in leukocytes, or treatment with an IRE1α pharmacological inhibitor, mitigated kidney inflammation and prolonged the survival of mice with systemic C. albicans infection. Therefore, controlling IRE1α hyperactivation may be useful for impeding the immunopathogenic progression of disseminated candidiasis.

Association between SNP rs4986790 and COVID-19 infection severity among Baghdad patients

Introduction and Aim: COVID-19, an infectious disease caused by the SARS-CoV-2 coronavirus, is distinguished by the manifestation of severe acute respiratory syndrome. Toll-like receptors (TLRs) are signaling molecules that play crucial roles in the innate immune system through their recognition of pathogen-associated molecular patterns in diverse microorganisms, including coronaviruses. The primary aim of this research was to investigate the plausible association between the TLR4 gene Asp299Gly polymorphism and the degree of infection severity among individuals who contracted COVID-19 in Baghdad, Iraq. Materials and Methods: This cross-sectional prospective study was carried out in Baghdad to investigate the Asp299Gly polymorphism within the TLR4 gene in a cohort of 90 patients diagnosed with Covid-19. Out of the total number of patients, 45 individuals exhibited symptoms indicative of a moderate infection, while the remaining 45 patients presented with a severe illness. The Asp299Gly polymorphism was analyzed using polymerase chain reaction (PCR) technique and restriction fragment length polymorphism (RFLP). Results: Genotyping for the Asp299Gly polymorphism showed only one among the 90 (1.1%) Covid-19 patients tested to be positive. No significant association was seen between covid-19 severity and Asp299Gly (P = 0·31) polymorphism. Conclusion: Our study found no association between SNP rs4986790 of TLR4 gene and COVID-19 severity among Covid-19 patients in Baghdad city.

Mechanisms and roles of the first stage of nodule formation in lepidopteran insects.

Nodule formation is a process of cellular immunity in insects and other arthropods with open circulatory systems. Based on histological observations, nodule formation occurs in 2 stages. The first stage occurs immediately after microbial inoculation and includes aggregate formation by granulocytes. The second stage occurs approximately 2-6 h later and involves the attachment of plasmatocytes to melanized aggregates produced during the first stage. The first stage response is thought to play a major role in the rapid capture of invading microorganisms. However, little is known regarding how granulocytes in the hemolymph form aggregates, or how the first stage of the immunological response protects against invading microorganisms. Since the late 1990s, our understanding of the molecules and immune pathways that contribute to nodule formation has improved. The first stage of nodule formation involves a hemocyte-induced response that is triggered by pathogen-associated molecular pattern (PAMP) recognition proteins in the hemolymph regulated by a serine proteinase cascade and cytokine (Spätzle) and Toll signaling pathways. Hemocyte agglutination proceeds through stepwise release of biogenic amine, 5-HT, and eicosanoids that act downstream of the Toll pathway. The first stage of nodule formation is closely linked to melanization and antimicrobial peptide (AMP) production, which is critical for insect humoral immunity. Nodule formation in response to artificial inoculation with millions of microorganisms has long been studied. It has recently been suggested that this system is the original natural immune system, and enables insects to respond to a single invading microorganism in the hemocoel.

Functions of MAP3Ks in antiviral immunity.

Immune signal transduction is crucial to the body's defense against viral infection. Recognition of pathogen-associated molecular patterns by pattern recognition receptors (PRRs) activates the transcription of interferon regulators and nuclear factor-κB (NF-κB); this promotes the release of interferons and inflammatory factors. Efficient regulation of type I interferon and NF-κB signaling by members of the mitogen-activated protein (MAP) kinase kinase kinase (MAP3K) family plays an important role in antiviral immunity. Elucidating the specific roles of MAP3K activation during viral infection is essential to develop effective antiviral therapies. In this review, we outline the specific regulatory mechanisms of MAP3Ks in antiviral immunity and discuss the feasibility of targeting MAP3Ks for the treatment of virus-induced diseases.

MYB44 regulates PTI by promoting the expression of EIN2 and MPK3/6 in Arabidopsis

The plant signaling pathway that regulates pathogen-associated molecular pattern (PAMP)-triggered immunity (PTI) involves mitogen-activated protein kinase (MAPK) cascades that comprise sequential activation of several protein kinases and the ensuing phosphorylation of MAPKs, which activate transcription factors (TFs) to promote downstream defense responses. To identify plant TFs that regulate MAPKs, we investigated TF-defective mutants of Arabidopsis thaliana and identified MYB44 as an essential constituent of the PTI pathway. MYB44 confers resistance against the bacterial pathogen Pseudomonas syringae by cooperating with MPK3 and MPK6. Under PAMP treatment, MYB44 binds to the promoters of MPK3 and MPK6 to activate their expression, leading to phosphorylation of MPK3 and MPK6 proteins. In turn, phosphorylated MPK3 and MPK6 phosphorylate MYB44 in a functionally redundant manner, thus enabling MYB44 to activate MPK3 and MPK6 expression and further activate downstream defense responses. Activation of defense responses has also been attributed to activation of EIN2 transcription by MYB44, which has previously been shown to affect PAMP recognition and PTI development. AtMYB44 thus functions as an integral component of the PTI pathway by connecting transcriptional and posttranscriptional regulation of the MPK3/6 cascade.

Mutating Amino Acids to Analyze the Effects on NADase Activity in Uropathogenic Escherichia coliand Acinetobacter baumanniiTIR proteins

Abstract Toll/interleukin-1 receptor/resistance protein (TIR) domains are crucial components in the innate immune system. In mammalian cells, TIR domains are found in Toll-like receptors (TLRs) which activate innate immune responses upon recognition of pathogen-associated molecular patterns and danger-associated molecular patterns. In contrast, TIR domains in prokaryotic cells may be linked to bacterial evasion of the innate immune system. To evade immune system defenses, Uropathogenic E. coli utilize TIR domains, like TcpC, to inhibit TLR signaling pathways. TcpC also has NADase activity which could have a role in immune evasion; we are interested in identifying amino acids important for TcpC’s NADase activity. Previously, we were able to determine that a conserved amino acid, glutamate, is important for NADase activity and that a conserved aspartic acid was crucial for NADase functionality for the additional bacterial TIR protein found in bacteria Acenitobacter baumanii (AbTIR). We hypothesized that the conserved aspartic acid may play a role in TcpC NADase activity. To support our hypothesis, we created an aspartic acid (D) to alanine (A) mutation using site-directed mutagenesis, tested to see if the mutation in TcpC affected NADase activity, and compared the effect of the TcpC DA mutation with the DA mutation from AbTIR. Results show that the DA mutants lost NADase activity, suggesting that the conserved aspartic acid is important for NADase activity in both TcpC and AbTIR. By determining which amino acids are critical for NADase activity, we can use this information for drug development for diseases that might be associated with TIR activity and innate immune evasion. Funded by NIH R25Act GM058264

The Role of Toll-like Receptors (TLRs) and Their Related Signaling Pathways in Viral Infection and Inflammation

Toll-like receptors (TLRs) belong to a powerful system for the recognition and elimination of pathogen-associated molecular patterns (PAMPs) from bacteria, viruses, and other pathogens [...].

Broader Function of Ficolins in Infectious Diseases

In the innate immune system, a diverse of pattern recognition molecules are important to prevent infection and maintain endogenous homeostasis. Ficolins are novel soluble recognition molecule, which sense Pathogen-Associated Molecular Patterns (PAMP) on microbes and abnormal structures on self-cells. Ficolins have been widely identified in animals from invertebrates to mammals. Although detailed comprehension about each ficolin is obscure, current information suggests that ficolins have a crucial role in host defense and are linked with many diseases. Ficolins function within innate immunity via the recognition of Pathogen-Associated Molecular Patterns (PAMPs) on microbial pathogens via two main mechanisms: (i) assembly of the Membrane Attack Complex (MAC), consisting of C5b-C9 proteins, which can directly lyse the bacterial membrane, and (ii) function as opsonins, potentiating the functions of immune cells. Complement activation may initiate positive responses against infections, but on the other hand, could exacerbate tissue damage or contribute to adverse side effects. Notably, there is mounting evidence implicating ficolins in the recognition and removal of numerous bacterial, viral, fungal, and parasitic pathogens in recent years. Additionally, there has been expanding evidence highlighting that cross-talk within these key complement immune proteins during the different infectious stages, enhance susceptibility to colonization by pathogens and dysfunctional immune responses. This review provides an overview of our up-to-date knowledge about ficolins, especially a broader perspective of the human ficolins and their mouse homologues.

Pathogen Recognition-Driven Dendritic Cell-Specific Gene Silencing and Editing

Dendritic cells (DCs) play an essential role in both the induction of the immune response and the maintenance of immune tolerance, with any malfunction of DCs potentially causing several diseases. While gene-based therapy for DC manipulation is a promising approach, it remains challenging due to the lack of efficient delivery systems for DC targeting. Herein, we describe a novel bacterial nanomedicine (BNM) system for pathogen recognition-mediated DCs-specific gene silencing and gene editing. BNMs contain components from bacterial outer membranes and achieve efficient DC targeting through the recognition of pathogen-associated molecular patterns by pattern recognition receptors on DCs. The targeting efficiency of BNMs is reduced in DCs lacking toll-like receptor 4, which is responsible for recognizing lipopolysaccharide, a major component of the bacterial outer membrane. As a proof-of-concept demonstration, we present gene-based therapy mediated by BNMs for enhancing antigen cross-presentation in DCs, which generates a remarkable antitumor effect.

Impact of Selected Bacterial and Viral Toll-like Receptor Agonists on the Phenotype and Function of Camel Blood Neutrophils.

Innate recognition of pathogens depends on the interaction between microbial structures known as pathogen-associated molecular patterns (PAMPs) and pattern recognition receptors (PRRs) in host cells. Toll-like receptors (TLR) are among the most important PRRs being expressed on and in a wide range of immune cell types. Studies on the interaction mechanisms between different pathogen species and the immune system of the dromedary camel are still scarce. The present study aimed to investigate the immunomodulatory effect of synthetic bacterial and viral TLR ligands on some phenotypic properties and selected functions of neutrophils purified from dromedary camel blood. Neutrophils were separated from camel blood (n = five animals) and were stimulated in vitro with the TLR ligands LPS, Pam3CSK4, R848 (Resiquimod), and Poly IC or were left without stimulation. Stimulation with the protein kinase C activator phorbol 12-myristate 13-acetate (PMA) was used as a positive control stimulation. Shape change, phagocytosis activity, ROS production, the expression of cell surface markers, and cell vitality were compared between stimulated and non-stimulated cells. With exception of the TLR3 agonist Poly IC, all TLR ligands used showed the potential to stimulate camel neutrophils resulting in increased cell size and the upregulation of CD18 and CD14 on their surface. Similarly, the phagocytosis activity of camel neutrophils was significantly improved after priming with all TLR ligands, except Poly IC, which, in contrast, resulted in a reduced percentage of phagocytosis-positive cells. In contrast to stimulation with PMA, which induced a significant ROS production in camel neutrophils, none of the TLR ligands used stimulated ROS generation in neutrophils. Only stimulation with Pam3CSK4 increased the expression of MHCII molecules on camel neutrophils, resulting in an expanded MHCIIhigh fraction within camel neutrophils. Our study indicates selective immunomodulating effects of TLR agonists on purified camel neutrophils without affecting their vitality.

Role of inflammasomes NLRC4 in pathogenesis of leprosy

Mycobacterium leprae is the organism responsible for causing leprosy, a persistent contagious illness. The inflammasome is a complex of cytosolic proteins that mediates the inflammatory response in response to pathogen-associated molecular patterns (PAMPs) or damage-associated molecular patterns (DAMPs), the latter of which is responsible for the maturation of caspase 1, secretion of IL-1 and IL-18, and a type of cell death known as pyroptosis. One protein, interleukin-1 conversion enzyme (ICE)-protease activating factor, was found to be responsible for initiating caspase-1. (IPAF). The amino-terminal CARD domain and its surrounding amino acids confirmed its membership in the NLR protein family, prompting the nomenclature change to NLRC4. In reaction to bacterial infections that target the cytoplasm of host cells, like M. tuberculosis and M. leprae, new data indicates that the NLRP3 inflammasome is involved in the inflammatory response caused by caspase-11. Activation of the NLRP3 inflammasome follows a classical pathway that begins with the recognition of PAMPs or DAMPs by TLRs, which then activates nuclear factor kappa B (NF-B)-mediated signaling and up-regulates transcription of inactive NLRP3, pro-IL-1, and pro-IL-18. Oligomerization of NLRP3 is the second stage, which is then followed by the formation of a complex containing NLRP3, ASC, and pro-caspase-1. This results in the synthesis and release of mature IL-1 and IL-18, as well as the self-activation of pro-caspase-1 into the enzymatically active form by proteolytic cleavage. The clinical course of an infection depends on the result of this first interaction, and it now appears that NLRP1, NLRP3, caspase 1, IL-1, and IL-18 collaborate in a concerted effort to trigger this early reaction.

Plant microbiota dysbiosis and the Anna Karenina Principle.

Microorganisms are associated with all plants, recently leading to the hologenome concept. We reviewed the assembly processes of plant microbiota and analyzed its structure during the emergence of dysbioses. In particular, we discussed the Anna Karenina Principle (AKP) based on Leo Tolstoy's assertion applied to plant microbiota: 'All healthy microbiota are alike; each disease-associated microbiota is sick in its own way.' We propose the AKP to explain how stochastic processes in plant microbiota assembly due to several external stressors could lead to plant diseases. Finally, we propose the AKP to conceptualize plant dysbioses as a transitory loss of host capacity to regulate its microbiota, implying a loss of function that leads to a reduction of the host's fitness.

Development and evaluation of the Galleria mellonella (greater wax moth) infection model to study Brucella host-pathogen interaction.

Brucellosis is a zoonotic disease caused by Gram-negative bacteria of the genus Brucella. These pathogens cause long-lasting infections, a process in which Brucella modifications in the lipopolysaccharide (LPS) and envelope lipids reduce pathogen-associated molecular pattern (PAMP) recognition, thus hampering innate immunity activation. In vivo models are essential to investigate bacterial virulence, mice being the most used model. However, ethical and practical considerations impede their use in high-throughput screening studies. Although lacking the complexity of the mammalian immune system, insects share key-aspects of innate immunity with mammals, and Galleria mellonella has been used increasingly as a model. G. mellonella larvae have been shown useful in virulence analyses, including Gram-negative pathogens like Klebsiella pneumoniae and Legionella pneumophila. To assess its potential to studyBrucella virulence, we first evaluated larva survival upon infection with representative Brucella species (i.e.B. abortus 2308W, B. microti CCM4915 and B. suis biovar 2) and mutants in the VirB type-IV secretion system (T4SS) or in the LPS-O-polysaccharide (O-PS). As compared to K.pneumoniae, the Brucella spp. tested induced a delayed and less severe mortality profile consistent with an escape of innate immunity detection. Brucella replication within larvae was affected by the lack of O-PS, which is reminiscent of their attenuation in natural hosts. On the contrary, replication was not affected by T4SS dysfunction and the mutant induced only slightly less mortality (not statistically significant) than its parental strain. We also evaluated G. mellonella to efficiently recognise Brucella and their LPS by quantification of the pro-phenoloxidase system and melanisation activation, using Pseudomonas LPS as a positive control. Among the brucellae, only B. microti LPS triggered an early-melanisation response consistent with the slightly increased endotoxicity of this species in mice. Therefore, G. mellonella represents a tool to screen for potential Brucella factors modulating innate immunity, but its usefulness to investigate other mechanisms relevant in Brucella intracellular life is limited.

Polymorphism Evaluation of TLR2 Gene Associated with Endometritis Infection in Buffalo Reared in Egypt

Background and Aim: Toll-like receptors (TLRs) are important for the recognition of pathogen-associated molecular patterns. Single nucleotide polymorphisms (SNPs) within TLRs have a potential impact on the alteration of susceptibility or resistance to inflammatory diseases. This work focused on a case-control study for the distribution of SNPs in TLR2 gene to test their role for endometritis occurrence in river buffalo.
 Materials and Methods: Egyptian buffaloes from the slaughterhouse were tested, where forty samples divided into apparently healthy uteri (20n) and clinically infected ones (20n) were used to detect the genetic association between TLR2 gene SNPs and endometritis disease.
 Results: Nineteen novel polymorphic sites were identified. Three SNPs were found to be statistically significant. AA genotype at 5`UTR and CC genotype at the coding region had significant association with susceptibility to endometritis, while GG genotype at 5`UTR had significant association with resistance to endometritis. Polyphen 2 analysis revealed three amino acids substitutions in TLR2 protein having potential functional significance. Haplotype reconstruction revealed the statistical significance of haplotype frequencies between cases and controls indicating its association with the occurrence of endometritis.
 Conclusions: It is to be concluded that the innate immune activation response may be interfered by the effect of polymorphisms and mutations of TLRs due to the reduction of the protein ability to recognize Pathogen associated Molecular pattern (PAMPs).

Understanding the role of Toll-like receptors in lung cancer immunity and immunotherapy

Lung cancer is currently the leading cause of cancer-related deaths worldwide. Significant improvements in lung cancer therapeutics have relied on a better understanding of lung cancer immunity and the development of novel immunotherapies, as best exemplified by the introduction of PD-1/PD-L1-based therapies. However, this improvement is limited to lung cancer patients who respond to anti-PD-1 immunotherapy. Further improvements in immunotherapy may benefit from a better understanding of innate immune response mechanisms in the lung. Toll-like receptors (TLRs) are a key component of the innate immune response and mediate the early recognition of pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs). TLR signaling modulates the tumor microenvironment from "cold" to "hot" leading to immune sensitization of tumor cells to treatments and improved patient prognosis. In addition, TLR signaling activates the adaptive immune response to improve the response to cancer immunotherapy through the regulation of anti-tumor T cell activity. This review will highlight recent progress in our understanding of the role of TLRs in lung cancer immunity and immunotherapy.