The TLR4 +896 polymorphism is not associated with lipopolysaccharide hypo-responsiveness in leukocytes

Infection, Inflammation, and Immunity in Sepsis

Sepsis is triggered by microbial infection, injury, or even major surgery. Both innate and adaptive immune systems are involved in its pathogenesis. Cytoplasmic presence of DNA or RNA of the invading organisms or damaged nuclear material (in the form of micronucleus in the cytoplasm) in the host cell need to be eliminated by various nucleases; failure to do so leads to the triggering of inflammation by the cellular cGAS-STING system, which induces the release of IL-6, TNF-α, and IFNs. These cytokines activate phospholipase A2 (PLA2), leading to the release of polyunsaturated fatty acids (PUFAs), gamma-linolenic acid (GLA), arachidonic acid (AA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA), which form precursors to various pro- and anti-inflammatory eicosanoids. On the other hand, corticosteroids inhibit PLA2 activity and, thus, suppress the release of GLA, AA, EPA, and DHA. PUFAs and their metabolites have a negative regulatory action on the cGAS-STING pathway and, thus, suppress the inflammatory process and initiate inflammation resolution. Pro-inflammatory cytokines and corticosteroids (corticosteroids > IL-6, TNF-α) suppress desaturases, which results in decreased formation of GLA, AA, and other PUFAs from the dietary essential fatty acids (EFAs). A deficiency of GLA, AA, EPA, and DHA results in decreased production of anti-inflammatory eicosanoids and failure to suppress the cGAS-STING system. This results in the continuation of the inflammatory process. Thus, altered concentrations of PUFAs and their metabolites, and failure to suppress the cGAS-STING system at an appropriate time, leads to the onset of sepsis. Similar abnormalities are also seen in radiation-induced inflammation. These results imply that timely administration of GLA, AA, EPA, and DHA, in combination with corticosteroids and anti-IL-6 and anti-TNF-α antibodies, may be of benefit in mitigating radiation-induced damage and sepsis.

Genetic polymorphism in CD14 gene, a co-receptor of TLR4 associated with non-alcoholic fatty liver disease

AIM

To evaluate the pathogenic role of toll-like receptor (TLR) gene polymorphisms in patients with non-alcoholic fatty liver disease (NAFLD).

METHODS

Two hundred and fifty subjects (NAFLD = 200, healthy volunteers = 50) underwent polymerase chain reaction and restriction fragment length polymorphism to assess one polymorphism in the toll-like receptor 2 (TLR2) gene (A753G), two polymorphisms in the TLR4 gene (TLR4 Asp299Gly and Thr399Ile allele), and two polymorphisms in the cluster of differentiation 14 (CD14) (C-159T and C-550T) gene, a co-receptor of TLR4. Association of TLR gene polymorphisms with NAFLD and its severity was evaluated by genetic models of association.

RESULTS

On both multiplicative and recessive models of gene polymorphism association, there was significant association of CD14 C (-159) T polymorphism with NAFLD; patients with TT genotype had a 2.6 fold increased risk of developing NAFLD in comparison to CC genotype. There was no association of TLR2 Arg753Gln, TLR4 Asp299Gly, Thr399Ile, and CD14 C (-550) T polymorphisms with NAFLD. None of the TLR gene polymorphisms had an association with histological severity of NAFLD.

CONCLUSION

Patients with CD14 C (-159) T gene polymorphism, a co-receptor of TLR4, have an increased risk of NAFLD development.

Genetic Susceptibility to Fungal Infections: What is in the Genes?

The development of severe fungal infections has long been associated with traditional risk factors such as profound immunosuppression, yet it remains challenging to understand why under similar conditions only some patients will develop these infections while others will not. Recent studies have demonstrated the importance of host genetic variation in influencing the severity and susceptibility to invasive fungal infections (IFIs). In this review, we examine selected primary immunodeficiencies characterized by their vulnerability to a narrow range of fungal pathogens, and then focus on recently identified genetic polymorphisms associated with an increased susceptibility to IFIs.

LPS-mediated production of pro/anti-inflammatory cytokines and eicosanoids in whole blood samples: biological effects of +896A/G TLR4 polymorphism in a Sicilian population of healthy subjects

Toll-like receptors (TLRs) are the principal mediators of rapid microbial recognition: the lipopolysaccharide (LPS) receptor TLR4 seems to have a paradigmatic role. Single nucleotide polymorphisms (SNPs) in the TLR4 gene, such as +896A/G, known to attenuate receptor signaling, have been described. The +896A/G SNP is significantly less frequent in patients with myocardial infarction, Alzheimer's disease or prostate cancer, whereas it is overrepresented in centenarians. To clarify and confirm the biological effects of +896A/G SNP and its role in the pathophysiology of age-related diseases and longevity, we assessed the levels of IL-6, TNF-α, IL-10 and eicosanoids (LTB4 and PGE2) in LPS-stimulated whole blood samples in vitro of 50 young healthy Sicilians, screened for the presence of this SNP. To evaluate the possible influence of SNPs in PTGS2 and 5-Lo genes on eicosanoid production, the enrolled individuals were also genotyped for -765G/C PTGS2 and -1708G/A 5-Lo SNPs. Both pro-inflammatory cytokines and eicosanoids were significantly lower in carriers bearing the TLR4 mutation, whereas the anti-inflammatory IL-10 values were higher. On the basis of data reported herein, some suggestions can be drawn. First, pathogen load, by interacting with the host genotype, determines the type and intensity of inflammatory responses, according to the pro-inflammatory status and tissue injury, implicated in the pathophysiology of major age-related diseases. Second, adequate control of inflammatory response might reduce the risk of these diseases, and, reciprocally, might increase the chance of extended survival in an environment with reduced antigen (that is, pathogen) load.

The additive contribution from inflammatory genetic markers on the severity of cardiovascular disease

Inflammation plays a key role in the development of atherosclerosis. Genetic differences in molecules related to inflammation have therefore been linked to the susceptibility for and severity of atherosclerosis. We hypothesized that the additive contribution from different genes of importance for inflammation would enhance the severity of cardiovascular disease. Blood samples were collected from 230 adults admitted for elective coronary angiography. A total of 130 patients had significant (>50%) stenosis in at least one main coronary artery branch and 100 had not. Six polymorphisms in five different genes were analysed: myeloperoxidase (MPO) -129G/A and -463G/A, toll-like receptor 4 (TLR4) Asp299Gly, interleukin-6 (IL6) -174G/C, surfactant protein D (SFTPD) Met11Thr and regulated upon normal T-cell expressed and secreted (CCL5) -403G/A. The IL6 polymorphism was significantly associated (P = 0.017) to angiographic significant coronary artery disease, and this relation remained after adjustment for age, gender, smoking and hypercholesterolaemia (P = 0.007). The TLR4 (P = 0.050) and SFTPD (P = 0.058) polymorphisms were also associated with the presence of coronary stenosis in univariate but not in multivariate analyses. For MPO and CCL5 no associations were found. There was a significant linear association between the number of high-risk gene variants (IL6-174CC, SFTPD 11CC and TLR4 299AA) and the proportion of patients with coronary artery disease (P < 0.0005). Inherited factors related to inflammation may increase susceptibility for severe coronary artery disease. Furthermore, the additive contribution from different inflammatory genetic markers strongly enhances the individual severity of cardiovascular disease.

Variation in the TLR4 gene influences the risk of organ failure and shock posttrauma: a cohort study

BACKGROUND

Genetic variation contributes to risk and outcomes of sepsis. We sought to determine whether variation in inflammation related genes is associated with severity of sepsis in trauma patients.

METHODS

A cohort of severely injured Caucasian patients was studied and genotyped for candidate single nucleotide polymorphisms (SNPs). These were toll-like receptor 4 (TLR4) A896G, tumor necrosis factor-alpha G-308A, interleukin-6 G-174C, interleukin-1beta C-31T, and cluster of differentiation marker 14C-159T. SNP genotypes among patients with sepsis and complicated sepsis were analyzed by chi2 and logistic regression. Six haplotype-tagging SNPs in the TLR4 gene were subsequently examined to analyze their influence on TLR4 A896G SNPs relationship to sepsis severity.

RESULTS

We enrolled 598 patients. Complicated sepsis developed in 147 (25%). Adjusting for independent risk factors, carriage of the variant TLR4 896 G allele was associated with decreased risk of complicated sepsis (odds ratio = 0.3, 95% confidence interval, 0.1-0.7, p = 0.008). Furthermore, two haplotypes seemed to better characterize this risk than the variant TLR4 896G allele. The variant TLR4 896G allele is linked to one common haplotype, which seems to confer a considerably reduced risk of complicated sepsis. (aOR = 0.2 95% confidence interval, 0.05-0.7, p = 0.01).

CONCLUSIONS

Variation within TLR4 gene is associated with severity of posttraumatic sepsis. This risk may not be solely related to TLR4 A896G SNP. It is likely that other, uncharacterized variations in the TLR4 gene contribute to sepsis severity. A thorough evaluation of variability within the TLR4 gene is needed to characterize sepsis risk.

Role of Toll-like receptors in the development of sepsis

The outcome of sepsis and septic shock has not significantly improved in recent decades despite the development of numerous drugs and supportive care therapies. To reduce sepsis-related mortality, a better understanding of molecular mechanism(s) associated with the development of sepsis and sepsis-related organ injury is essential. There is increasing evidence that Toll-like receptors (TLRs) play a key role in the mediation of systemic responses to invading pathogens during sepsis. However, the role of TLRs in the development of sepsis and in sepsis-related organ injury remains debatable. In this review, we focus on the biological significance of TLRs during sepsis. Medline was searched for pertinent publications relating to TLRs, with emphasis on their clinical and pathophysiological importance in sepsis. In addition, a summary of the authors' own experimental data from this field was set in the context of current knowledge regarding TLRs. In both animal models and human sepsis, TLRs are highly expressed on monocytes/macrophages, and this TLR expression may not simply be a ligand-specific response in such an environment. The fact that TLR signaling enables TLRs to recognize harmful mediators induced by invading pathogens may be associated with a positive feedback loop for the inflammatory response among different cell populations. This mechanism(s) may contribute to the organ dysfunction and mortality that occurs in sepsis. A better understanding of TLR biology may unveil novel therapeutic approaches for sepsis.

Challenges for modeling and interpreting the complex biology of severe injury and inflammation

Human injury is associated with inflammatory responses that are modulated by the acute and chronic activity of endogenous factors and exogenous interventions. A characteristic feature of chronic, severe inflammatory states is the diminished signal output variability of many organ systems, including innate immune responsiveness and endogenous neural and endocrine-mediated functions. The attenuation of signal/response variability and integration of feedback capacity may contribute to systemic and tissue-specific deterioration of function. Some well-intentioned therapies directed toward support of systemic and tissue functions may actually promote the loss of system(s) adaptability and contribute to adverse outcomes in severely stressed patients. In vivo and in silico models of stress, injury, and infection have yet to fully define the influences of ongoing stressful stimulae as well as genetic variation and epigenetic factors in the context of an evolving inflammatory state. Experimental and human models incorporating variable, antecedent stress(es) and altered neuroendocrine rhythms might approximate the altered adaptability in immune and organ function responses. Such models may also provide insights into the salient mechanisms of risk and outcome more precisely than do the constrained study conditions of current animal or human models of systemic inflammation.

Polymorphisms in Toll-like receptors-2 and -4 are not associated with disease manifestations in acute Q fever

Coxiella burnetii is a macrophage-tropic, Gram-negative organism, which causes acute Q fever infection in humans. This zoonotic infection causes illness ranging from asymptomatic seroconversion to severe and protracted disease featuring hepatitis and pneumonia. Interactions between C. burnetii lipopolysaccharide (LPS) and host Toll-like receptors (TLR)-2 and -4 have been implicated in pathogen recognition, phagocytosis and signaling responses. Nonconservative single nucleotide polymorphisms in the coding regions of TLR-2 (Arg677Trp and Arg753Gln) and TLR-4 (Asp299Gly) have been found to correlate with mycobacterial infections and Gram-negative sepsis respectively. Associations between the TLR-2 and -4 polymorphisms, illness characteristics and immune response parameters were examined in subjects with acute Q fever (n=85) and comparison subjects with viral infections (n=162). No correlation was demonstrated between these polymorphisms and susceptibility to Q fever, illness severity or illness course.

The role of the Toll receptor pathway in susceptibility to inflammatory bowel diseases

The intestinal flora has long been thought to play a role either in initiating or in exacerbating the inflammatory bowel diseases (IBD). Host defenses, such as those mediated by the Toll-like receptors (TLR), are critical to the host/pathogen interaction and have been implicated in IBD pathophysiology. To explore the association of genetic variation in TLR pathways with susceptibility to IBD, we performed a replication study and pooled analyses of the putative IBD risk alleles in NFKB1 and TLR4, and we performed a haplotype-based screen for association to IBD in the TLR genes and a selection of their adaptor and signaling molecules. Our genotyping of 1539 cases of IBD and pooled analysis of 4805 cases of IBD validates the published association of a TLR4 allele with risk of IBD (odds ratio (OR): 1.30, 95% confidence interval (CI): 1.15-1.48; P=0.00017) and Crohn's disease (OR: 1.33, 95% CI: 1.16-1.54; P=0.000035) but not ulcerative colitis. We also describe novel suggestive evidence that TIRAP (OR: 1.16, 95% CI: 1.04-1.30; P=0.007) has a modest effect on risk of IBD. Our analysis, therefore, offers additional evidence that the TLR4 pathway - in this case, TLR4 and its signaling molecule TIRAP - plays a role in susceptibility to IBD.

Gingival epithelial cells heterozygous for Toll-like receptor 4 polymorphisms Asp299Gly and Thr399ile are hypo-responsive to Porphyromonas gingivalis

The Toll-like receptor (TLR)4 is the major sensor for bacterial lipopolysaccharide and its two common co-segregating polymorphisms, Asp299Gly and Thr399Ile, which occur at a frequency of between 6 and 10%, have been associated with infectious diseases, LPS hypo-responsiveness and cardiovascular disease. Porphyromonas gingivalis is a Gram-negative bacterium implicated in chronic periodontitis and is a known TLR4 and TLR2 agonist. We obtained two gingival epithelial cell primary cultures from subjects heterozygous for the TLR4 polymorphism Asp299Gly and compared response characteristics with similar cells from patients (four) with the wild-type TLR4 genes. Cytokine responses and transcriptome profiles of gingival epithelial cell primary culture cells to TNFalpha challenge were similar for all primary epithelial cell cultures. P. gingivalis challenge, however, gave markedly different responses for Asp299Gly heterozygous and wild-type epithelial cell cultures. The epithelial cells heterozygous for the TLR4 polymorphism Asp299Gly were functionally hypo-responsive, evidenced by differences in BD-2 mRNA expression, mRNA response profile by microarray analysis and by pro-inflammatory and chemokine cytokines at the protein and mRNA level. These findings emphasize variance in human epithelial cell TLRs, linked with Asp299Gly carriage, which results in a hypo-responsive epithelial cell phenotype less susceptible to Gram-negative diseases and associated systemic conditions.

Gender influences in vivo human responses to endotoxin

Gender appears to influence systemic and organ-specific inflammatory sequelae of ischemia-reperfusion and infectious challenge in many animal models. Despite the protection provided by female gender, androgen blockade, and/or estrogen administration in such experimental studies, many questions remain regarding the influence of gender dimorphism upon human responses to injury. We hypothesized that the administration of low-dose lipopolysaccharide (LPS) to otherwise healthy, young adults would provide insights regarding the influence of gender upon physiological and innate immune system responses to a prototypic inflammatory stimulus. To this end, 72 adult subjects (48 men, aged 29 +/- 1.0 years; 24 women, aged 26 +/- 1.0 years) were prospectively evaluated before and after the i.v. administration of LPS (2 ng/kg). All subjects developed symptoms within 1.0 to 1.5 h after LPS, and the men exhibited a greater increase in core temperature (2.1 +/- 0.1 degrees C) compared with the women (1.4 +/- 0.1 degrees C) (P < 0.001). In addition, the men exhibited a greater maximum decrease in mean arterial pressure (-13.0 +/- 1.3 mmHg) compared with the women (-8 +/- 1.3 mmHg) (P < 0.02). The changes in temperature and mean arterial pressure occurred without detectable differences between the male and female cohort responses of circulating white blood cell count and cortisol or cytokine levels. These results suggest that soluble inflammatory mediators generated by in vivo endotoxin activation of the innate immune system are insufficient to explain the resultant gender-specific phenotypic differences observed in young, adult humans.

Inflammatory networks in ageing, age-related diseases and longevity

Inflammation is considered a response set by the tissues in response to injury elicited by trauma or infection. It is a complex network of molecular and cellular interactions that facilitates a return to physiological homeostasis and tissue repair. The individual response against infection and trauma is also determined by gene variability. Ageing is accompanied by chronic low-grade inflammation state clearly showed by 2-4-fold increase in serum levels of inflammatory mediators. A wide range of factors has been claimed to contribute to this state; however, the most important role seems to be played by the chronic antigenic stress, which affects immune system thorough out life with a progressive activation of macrophages and related cells. This pro-inflammatory status, interacting with the genetic background, potentially triggers the onset of age-related inflammatory diseases as atherosclerosis. Thus, the analysis of polymorphisms of the genes that are key nodes of the natural immunity response might clarify the patho-physiology of age-related inflammatory diseases as atherosclerosis. On the other hand, centenarians are characterized by marked delay or escape from age-associated diseases that, on average, cause mortality at earlier ages. In addition, centenarian offspring have increased likelihood of surviving to 100 years and show a reduced prevalence of age-associated diseases, as cardiovascular disease (CVD) and less prevalence of cardiovascular risk factors. So, genes involved in CVD may play an opposite role in human longevity. Thus, the model of centenarians can be used to understand the role of these genes in successful and unsuccessful ageing. Accordingly, we report the results of several studies in which the frequencies of pro-inflammatory alleles were significantly higher in patients affected by infarction and lower in centenarians whereas age-related controls displayed intermediate values. These findings point to a strong relationship between the genetics of inflammation, successful ageing and the control of cardiovascular disease at least in men, in which these studies were performed. These data are also briefly discussed in the light of antagonistic pleiotropy theory and in order to pursuit a pharmacogenomics approach.

Toll-like receptor (TLR) 4 polymorphism Asp299Gly is not associated with disease course in Dutch sarcoidosis patients

The aetiology of sarcoidosis, a systemic disorder characterized by the formation of non-caseating granulomas in variable organs, remains enigmatic. Clarification is hampered by heterogeneity in disease phenotypes and course, due partly to the influence of a variety of genetic and environmental factors. Multiple studies have pointed towards bacteria as possible causative agents. Toll-like receptors (TLR) are innate immunity receptors important in the immune response against pathogens. TLR-4, together with CD14 and MD-2, is an essential receptor for the recognition of lipopolysaccharide (LPS), unique to the cell wall of Gram-negative bacteria. Recently, an association between TLR-4 polymorphism Asp299Gly, leading to a change in the extracellular domain of the receptor and possible hyporesponsiveness to LPS, and a chronic course of sarcoidosis was found in German patients. In the present study this polymorphism was genotyped in 156 Dutch sarcoidosis patients and 200 healthy Dutch controls using dual-labelled fluorescent oligonucleotides. No differences were found in allelic distributions between patients and controls (P = 0.79) or within the different clinical entities of the sarcoidosis group (P = 0.44). Importantly, there were no differences between the Dutch and German sarcoidosis patients (P = 0.62). However, the allelic distribution of the Asp299Gly polymorphism differed significantly between both control groups (P = 0.04). This study highlights the importance of testing a reported gene association in a distinct population when performing genetic association studies.

Protective and destructive immunity in the periodontium: Part 1--innate and humoral immunity and the periodontium

Based on the results of recent research in the field, the present paper will discuss the protective and destructive aspects of the innate vs. adaptive (humoral and cell-mediated) immunity associated with the bacterial virulent factors or antigenic determinants during periodontal pathogenesis. Attention will be focused on: (i) the Toll-like receptors (TLR), the innate immune repertoire for recognizing the unique molecular patterns of microbial components that trigger innate and adaptive immunity for effective host defenses, in some general non-oral vs. periodontal microbial infections; (ii) T-cell-mediated immunity, Th-cytokines, and osteoclastogenesis in periodontal disease progression; and (iii) some molecular techniques developed and used to identify critical microbial virulence factors or antigens associated with host immunity (using Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis as the model species). Therefore, further understanding of the molecular interactions and mechanisms associated with the host's innate and adaptive immune responses will facilitate the development of new and innovative therapeutics for future periodontal treatments.

Response to systemic endotoxemia among humans bearing polymorphisms of the Toll-like receptor 4 (hTLR4)

Mutations (Asp299Gly and Thr399Ile) in the human Toll-like receptor 4 (hTLR4) gene are reportedly associated with hyporesponsiveness to inhaled LPS in humans. It was hypothesized that normal volunteers with these hTLR4 mutations would manifest altered physiological responses to intravenous LPS administration. Human subjects (n = 57) were administered LPS (2 ng/kg) intravenously and monitored for vital signs (temperature, heart rate, mean arterial pressure). Blood-derived genomic DNA samples were evaluated using PCR to detect hTLR4 and TLR2 mutations. Heterozygous hTLR4 mutations were identified in 8 of the 57 subjects studied. Subjects with hTLR4 mutations demonstrated similar responses to LPS administration. The moderate systemic inflammatory response produced by intravenous LPS administration in human subjects is not modulated by the presence of heterozygous mutations in the hTLR4 gene.

The Toll-like receptor 4 (Asp299Gly) polymorphism is a risk factor for Gram-negative and haematogenous osteomyelitis

Osteomyelitis is a bone infection caused mostly by Staphylococcus aureus but also by Gram-negative bacteria. Toll-like receptors (TLRs), after recognizing microbial products, induce a signal in neutrophils, leading to NF-kappaB activation and transcription of pro-inflammatory genes. Polymorphisms in TLR2 (Arg753Gln) and TLR4 (Asp299Gly, Thr399Ile) genes are associated with bacterial infections, we therefore studied these polymorphisms in osteomyelitis patients. Homozygotes for the TLR4 (Asp299Gly) polymorphism were significantly more frequent among the 80 osteomyelitis patients than in the 155 healthy controls (3/80, 3.8%versus 0/155, 0%; P = 0.038). Carriers of one or two G alleles of this tlr4 polymorphism were more likely to have Gram-negative, haematogenous and/or chronic osteomyelitis than those without this mutation (P < 0.031). Patients with the TLR4 (Thr399Ile) mutant, which cosegregates with the TLR4 (Asp299Gly), were also carriers of this second polymorphism. No differences for the TLR2 (Arg753Gln) genotypes were found between patients and controls. Neutrophils of patients homozygous for the TLR4 (Asp299Gly) polymorphism showed lower LPS-induced apoptosis reduction, phosphorylation of the inhibitor of NF-kappaB, and lower IL-6 and TNF-alpha levels (P < 0.05). We report here for the first time an association between this TLR4 polymorphism and susceptibility to Gram-negative bacteria and haematogenous osteomyelitis.

The influence of gender on human innate immunity

BACKGROUND

Several experimental, clinical, and epidemiologic studies indicate a better prognosis in women after an infectious challenge. The monocyte/macrophage, as coordinators of the innate immune response to sepsis, secrete plasma inflammatory cytokines. Elevated plasma cytokine levels are inversely correlated with outcome. In addition, single-nucleotide polymorphisms related to these cytokine genes and in genes important for lipopolysaccharide (LPS) detection, particularly toll-like receptor-4, have been associated with variations in clinical outcome. We hypothesize that the gender differences in clinical outcome are due to measurable differences in cytokine responses and intracellular signaling, and these differences are independent of polymorphism carrier status.

METHODS

Venous blood samples from healthy subjects (56 men, 23 women) were incubated with LPS, and supernatant cytokine levels were determined by enzyme-linked immunosorbent assay. In a randomly chosen subgroup, (8 men, 4 women), peripheral blood mononuclear cells were isolated, and LPS-mediated intracellular mitogen-activated protein kinase (MAPK) phosphorylation was assayed via Western blot analysis. Each subject was screened for the following SNPs: tumor necrosis factor alpha (TNF-alpha) -308G/A, interleukin (IL)-6 -174G/C, IL-1beta -31C/T, and toll-like receptor-4 (TLR4) +896A/G.

RESULTS

Women produced significantly less LPS-induced TNF-alpha and IL-1beta but not IL-6. When the analysis was adjusted for the presence of each polymorphism, the differences in TNF-alpha and IL-1beta accumulation persisted. Female gender was associated with lower MAPK phosphorylation at each LPS concentration but was not statistically significant.

CONCLUSIONS

Gender-specific differences in LPS-induced TNF-alpha and IL-1beta were observed, possibly attributed to alterations in MAPK phosphorylation. Furthermore, studies investigating the influence of genomic variation on the innate immune response should address potential gender-related differences.

Genetic polymorphisms in sepsis

CONTEXT

Wide variability exists in the susceptibility to and outcome from sepsis even within similar intensive care unit populations. Some of this variability in the host may be due to genetic variation in genes coding for components of the innate immune response.

OBJECTIVE

To review the evidence for a genetic influence on the susceptibility to and outcome from sepsis.

DESIGN

Literature review.

PATIENTS

Variety of adult and pediatric patients with various critical illnesses and infections.

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

Susceptibility to clinical symptoms of sepsis and outcome as measured by severity of disease and mortality.

RESULTS

Polymorphisms in genes coding for proteins involved in the recognition of bacterial pathogens (Toll-like receptor 4, CD14, Fc(gamma)RIIa, and mannose-binding lectin) and the response to bacterial pathogens (tumor necrosis factor-alpha, interleukin (IL)-1alpha, IL-1beta, IL-1 receptor agonist, IL-6, IL-10, heat shock proteins, angiotensin I converting enzyme, plasminogen activator inhibitor-1) can influence the amount or function of the protein produced in response to bacterial stimuli. Evidence is discussed suggesting that some of these genetic polymorphisms influence the susceptibility to and outcome from sepsis.

CONCLUSION

Host genetic variability in the regulatory and coding regions of genes for components of the innate immune system may influence the susceptibility to and/or outcome from sepsis. The disparate results observed in many studies of polymorphisms in sepsis emphasize the need for future studies to be larger, to include the analysis of multiple polymorphisms, and to be better designed with respect to control populations to identify the degree of influence that genetic variability has on sepsis.