The lack of genetic association of the Toll-like receptor 2 (TLR2) Arg753Gln and Arg677Trp polymorphisms with rheumatic heart disease

Acute rheumatic fever (ARF) is a non-suppurative inflammatory disease after group A, beta haemolytic streptococcal pharyngitis. Certain individuals can develop ARF. This finding implies variability in host predisposition to ARF. A variety of studies have linked specific genetic markers with ARF or rheumatic heart disease (RHD) as a sequelae of ARF. For this purpose, we aimed to search the role of polymorphisms in Toll-like receptor-2 and -4 (TLR2 and TLR4) gene in Turkish patients with RHD. This study included a total 84 patients with RHD, ages ranging between 18 and 65, 25 male and 59 female, fulfilling the revised classification criteria of Jones. One hundred forty healthy unrelated persons were selected as a control group. Genotype analysis: DNA was extracted from whole blood. TLR4 gene (Asp 299Gly and Thr399Ile) and TLR2 gene (Arg753Gln and Arg677Trp) polymorphisms were genotyped by the previously reported method. Statistical analysis: binary logistic regression models were used. Results were expressed as odds ratios (OR) with corresponding 95% confidence intervals (95% CI). Significant level was predefined at 0.05. There was a significant difference for carrying Ile allele in the 399 position in the patients compared to healthy controls (OR = 5.26, 95% CI, 1.40-19.73, p = 0.014). In the TLR4 gene, Asp 299Gly polymorphism did not reach to a statistically significant value (OR = 3.02). We found no Arg753Gln polymorphism of the TLR2 gene in the patient group. There were three heterozygote samples in the healthy group. We did not detect Arg677Trp polymorphism of the TLR2 gene in both patient and control groups.     

Lack of association of single nucleotide polymorphisms in toll-like receptors 2 and 4 with enthesitis-related arthritis category of juvenile idiopathic arthritis in Indian population

Toll-like receptors 2 and 4 are over expressed in patients with enthesitis-related arthritis and cause increased production of pro-inflammatory cytokines. This aberrant functioning could be due to polymorphisms in TLR2 and TLR4. Hence, we genotyped ERA patients for Arg753Gln and Arg677Trp polymorphism in TLR2 gene and Asp299Gly and Thr399Ile polymorphism in TLR4 gene. DNA was extracted from blood from ERA patients and healthy controls. All four polymorphisms were studied by PCR–RFLP method. 200 healthy controls and 97 ERA patients were enrolled. All healthy controls and patients had wild-type allele for Arg753Gln and Arg677Trp TLR2 polymorphism. Regarding TLR4, Asp299Gly polymorphism A allele frequency was 90 % in controls and 96 % in patients (OR 2.7, 95 % CI 0.81–8.8). GG homozygous genotype was detected in one healthy control and was absent from patients. The TLR4 Thr399Ileu variant was not detected in patients. Out of 200 healthy controls, 10 were heterozygous (5 %) and only one was homozygous for rare variant (0.5 %). Polymorphisms in TLR2 and TLR4 are not associated with ERA.     

TLR4基因Asp299Gly及TLR2基因Arg753Glu、Arg677Trp多态性与中国湖北汉族炎症性肠病无相关性

目的:研究TLR4基因Asp299Gly及LTLR2基因 Arg753Glu及Arg677Trp多态性在中国汉族人群中的分布,探讨其与炎症性肠病的相关性．方法:采用聚合酶链反应-限制性片段长度多态性方法,检测120例中国湖北汉族炎症性肠病患者与110例正常对照者TLR4 基因ASp299Gly及TLR2基因Arg753Glu及 Arg677Trp基因型,分析该基因多态性与炎症性肠病以及临床亚型的相关性．结果:炎症性肠病患者和健康对照者均未检测出TLR4基因ASp299Gly及TLR2基因 Arg753Glu及Arg677Trp突变型．结论:TLR4基因Asp299Gly及TLR2基因 Arg753Glu及Arg677Trp基因多态性与中国湖北汉族人群炎症性肠病的易感性无相关性．     

TLR-2 Arg753Gln, TLR-4 Asp299Gly, and TLR-4 Thr399Ile polymorphisms in Henoch Schonlein purpura with and without renal involvement

Infections may trigger or aggravate glomerulonephritidis and renal vasculitis like Henoch Schonlein purpura (HSP). HSP is seen more frequently in patients with familial Mediterranean fever in which TLR-2 Arg753Gln polymorphism frequency is increased. Although renal involvement is the most important factor affecting the prognosis in HSP, it is not known which patients will have renal disease or why some patients have severe renal involvement while some others have mild renal disease. We investigated the role of TLR-2 and TLR-4 polymorphisms on the incidence and severity of renal involvement in HSP patients. We studied HSP patients with and without nephritis (n = 15 for each group) and healthy controls (n = 100). TLR-2 Arg753Gln and TLR-4 Asp299Gly/Thr399Ile polymorphisms were analyzed with polymerase chain reaction–restriction fragment length polymorphism method. The frequency of TLR-2 Arg753Gln, TLR-4 Asp299Gly, and Thr399Ile polymorphisms in healthy controls were 1, 3, and 2%, respectively. The frequencies of these polymorphisms were not different in HSP patients with or without nephritis compared to healthy controls. TLR-3 Arg753Gln, TLR-4 Asp299Gly, and Thr399Ile polymorphisms are not increased in HSP or HSP nephritis patients.     

Toll样受体及其基因多态性与感染性疾病关系的研究进展

Toll样受体是近年来发现的跨膜信号传递受体,他作为一种重要的模式识别受体(PRRs)在先天免疫中通过对病原体相关的分子模式(PAMPs)的识别发挥作用,通过刺激信号的级联反应诱导炎症因子和细胞因子产生,在抗感染中起重要作用.基因多态性影响机体对疾病的遗传易感性,TLRs的位点多态性与炎性应答损伤和感染性疾病的遗传易感性相关.目前多数研究表明TLR4的Asp299Gly和Thr399Ile,TLR2的Arg753Gln和Arg667Trp多态性与感染性疾病的发生相关,其他TLRs的基因多态性也有研究.本文就TLRs家族的功能及其基因多态性与感染性疾病的关系作一综述.     

The role of Toll-like receptor 4 Asp299Gly and Thr399Ile polymorphisms and CARD15/NOD2 mutations in the susceptibility and phenotype of Crohn's disease

BACKGROUND: We investigated the influence of 2 common Toll-like receptor 4 (TLR4) polymorphisms on susceptibility and disease characteristics of Crohn's disease (CD). METHODS: Genomic DNA from 204 patients with CD and 199 unrelated controls was analyzed for the presence of 2 single nucleotide polymorphisms in the TLR4 gene, resulting in the amino acid substitutions Asp299Gly and Thr399Ile. In addition, the carrier status for the 3 common CD-associated CARD15/NOD2 gene mutations, Arg702Trp, Gly908Arg, and 1007fs, was determined. The frequency of the different genotypes was compared, and a detailed genotype-phenotype correlation was performed. RESULTS: An almost 2-fold increase in the frequency of the TLR4 Asp299Gly phenotype was observed in patients with CD (14.2%) compared with healthy controls (7.5%, P = 0.038, odds ratio = 2.03). The prevalence of a stricturing phenotype was increased in patients heterozygous for 1 of the TLR4 polymorphisms studied (Asp299Gly, 34.5%; Thr399Ile, 36.7%) compared with patients with wild-type TLR4 (17.1% and 16.7%; P = 0.04 and 0.02, respectively). The presence of the Asp299Gly polymorphism in the absence of CARD15/NOD2 mutations was a particularly strong predictor of the stricturing disease phenotype that was present in 47.4% of the patients with Asp299Gly+/NOD2- compared with 10.1% of the patients with the Asp299Gly-/NOD2+ status (P = 0.0009; P = 0.0004 for Thr399Ile+/NOD2- versus Thr399Ile-/NOD2+). In contrast, there was a trend toward a higher prevalence of the penetrating phenotype in the TLR4-/NOD2+ group (71.6%) compared with the TLR4+/NOD2- group (47.4%, P = 0.059). CONCLUSIONS: The TLR4 Asp299Gly polymorphism is a risk factor for CD. TLR4 and CARD15/NOD2 mutations may contribute to distinct disease phenotypes.     

Association between Toll-like receptor 4 and inflammatory bowel disease

BACKGROUND: The human Toll-like receptor 4 (TLR4) participates in the innate response. Recently, the TLR4 variant Asp299Gly has been described to affect the response of this receptor to lipopolysaccharide. As such, there is a potentially important role of TLR4 in the pathogenesis of inflammatory bowel disease (IBD). We studied the involvement of TLR4 in IBD in a large population of Dutch patients with IBD and in family-based controls. METHODS: In 781 IBD cases and 315 controls, genotyping was performed forAsp299Gly and Thr399Ile variants and for 4 microsatellite markers flanking TLR4. Association analysis and the were applied. In addition, interaction of TLR4 with the caspase recruitment domain containing protein 15 gene (CARD15) was studied in patients with Crohn's disease (CD). RESULTS: The haplotype sharing statistic showed association at microsatellite marker D9S1864 with IBD (P = 0.0019), and in particular with CD (P = 0.0025) and at TLR406 with ulcerative colitis (UC; P = 0.027). No association was found for Asp299Gly and Thr399Ile. However, the frequencies of both variant allele carriers were higher among CD cases with a disease onset > or = 40 years than among controls. No evidence for interaction between TLR4 and CARD15 was found. CONCLUSIONS: Haplotype analysis shows that TLR4 is associated with both CD and UC. The Asp299Gly and Thr399Ile variants do not show an association with CD, UC, or IBD as a group, indicating that these polymorphisms are likely not the causal ones. We propose that the 2 polymorphisms are in linkage with (the) disease susceptibility variant(s) located elsewhere on TLR4.     

No evidence for involvement of the toll-like receptor (TLR) 4 gene Asp299Gly and Thr399Ile polymorphisms in susceptibility to primary gouty arthritis

Previous studies demonstrated that toll-like receptor (TLR) 4 was involved in the development of autoinflammatory disease including gouty arthritis (GA). TLR4 functional gene Asp299Gly and Thr399Ile polymorphisms play a role in some autoinflammatory disease susceptibility. We undertook this study to analyze the association between the genetic polymorphisms within TLR4 gene and the susceptibility to GA in Chinese Han people. Two functional variants, Asp299Gly and Thr399Ile, in the TLR4 gene were genotyped using 5′ exonuclease TaqMan^® technology from 218 male GA patients and 226 ethnically matched controls. None polymorphisms of Asp299Gly and Thr399Ile were detected in all GA cases and controls, which indicates that there is no evidence for involvement of the TLR4 gene Asp299Gly and Thr399Ile polymorphisms in susceptibility to primary GA in the Chinese Han population. Further studies with extended single nucleotide polymorphisms should be performed.     

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 nonalcoholic 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 Asp299 Gly and Thr399 Ile allele), and two polymorphisms in the cluster of differentiation 14(CD14)(C-159 T 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 Arg753 Gln, TLR4 Asp299 Gly, Thr399 Ile, 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.     

Analysis of TLR4 and TLR2 polymorphisms in inflammatory bowel disease in a Guangxi Zhuang population

AIM: To study the polymorphisms of toll-like receptor 4 (TLR4) gene Asp299Gly, Thr399Ile and TLR2 gene Arg753Gln, Arg677Trp and susceptibility to inflammatory bowel disease (IBD) in the Zhuang population from Guangxi, China.METHODS: A case-control study was performed from February 2007 to October 2011 which included 146 Zhuang patients with IBD in the experimental group and 164 healthy Zhuang subjects who acted as the control group. All patients and healthy subjects were from the Guangxi Zhuang Autonomous Region of China. Genomic DNA was extracted from intestinal tissue by the phenol chloroform method. TLR4 gene Asp299Gly, Thr399Ile and TLR2 gene Arg753Gln, Arg677Trp were amplified by polymerase chain reaction (PCR), and then detected by PCR-restriction fragment length polymorphism (RFLP).RESULTS: The TLR4 gene Asp299Gly was digested using Nco I restriction enzyme, and a single band of 249 bp was observed which showed that it was a wild type (AA). The TLR4 gene Thr399Ile was digested using Hinf Irestriction enzyme and only the wild type (CC) was detected. In addition, the TLR2 gene Arg677Trp was digested using Aci I restriction enzyme and only the wild type (CC) was detected. The TLR2 gene Arg753Gln was digested using Pst I restriction enzyme. Only the wild type (GG) as a single band of 254 bp was observed during RFLP. Overall, no heterozygous or homozygous single nucleotide polymorphism mutations were found in patients with Crohn’s disease and ulcerative colitis both in the TLR4 gene Asp299Gly, Thr399Ile and the TLR2 gene Arg677Trp, Arg753Gln in the Zhuang population from the Guangxi Zhuang Autonomous Region of China.CONCLUSION: The TLR4 gene Asp299Gly, Thr399Ile and TLR2 gene Arg753Gln, Arg677Trp polymorphisms may not be associated with IBD in the Zhuang population from the Guangxi Zhuang Autonomous Region of China.     

Toll-like receptor 4 gene polymorphisms and susceptibility to juvenile idiopathic arthritis

OBJECTIVES: To determine if polymorphisms within the Toll-like receptor 4 (TLR4) gene are associated and linked with juvenile idiopathic arthritis (JIA). To investigate any possible gene-gene (epistatic) interaction between TLR4 and macrophage migration inhibitory factor (MIF) gene polymorphisms. METHODS: 313 simplex families (each containing one affected JIA proband) were genotyped. Two known functionally important single nucleotide polymorphisms (SNPs) within the TLR4 gene (Asp299Gly and Thr399Ile) were typed by SNaPshot ddNTP primer extension and capillary electrophoresis.Single point and multipoint transmission disequilibrium tests (TDT) were carried out through the extended TDT and TDT phase packages for the two TLR4 SNPs. Epistatic interaction between TLR4 haplotypes and the previously JIA associated MIF CATT(7)-MIF-173*C promoter haplotype was investigated by chi(2) test and unconditional logistic regression in Stata version 7. RESULTS: No distortion from random inheritance was observed by single point analysis for TLR4 Asp299Gly (p = 0.89) or TLR4 Thr399Ile (p = 0.40). Similarly, no distortion in transmission was seen when the TLR4 haplotypes were studied (p = 0.54). Additionally, no evidence for gene-gene interaction between TLR4 polymorphisms and the previously associated MIF gene polymorphisms was found (p = 0.40). CONCLUSIONS: No linkage or association was seen for Asp299Gly or Thr399Ile SNPs of TLR4 with JIA susceptibility. No evidence of an epistatic interaction between these TLR4 polymorphisms and MIF polymorphisms was found.     

Toll-like receptor 4 gene polymorphisms and preeclampsia: lack of association in a Caucasian population

Preeclampsia is a multifactorial disorder with genetic and environmental components. As Toll-like receptor 4 (TLR4) has an essential role in innate immune response, which is exaggeratedly activated in preeclampsia, our aim was to investigate whether two single nucleotide polymorphisms (SNPs) of the TLR4 gene--Asp299Gly (A896G) and Thr399Ile (C1196T)--are associated with preeclampsia in a Caucasian population from Hungary. In a case-control study, we analyzed blood samples from 180 preeclamptic patients and 172 normotensive, healthy pregnant women with the polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) method. The linkage disequilibrium (LD) profile of the TLR4 gene was investigated and tag SNPs were identified using data from the International HapMap Project. There were no significant differences in the genotype and allele frequencies of Asp299Gly and Thr399Ile polymorphisms between the two study groups. Additionally, no significant difference was found in the distribution of the estimated haplotypes created by the two polymorphisms between the preeclamptic and the control group. Furthermore, no significant differences were detected in the genotype, allele and haplotype frequencies of Asp299Gly and Thr399Ile TLR4 SNPs between patients with mild and severe preeclampsia, between patients with late and early onset of the disease, or between preeclamptic patients with and without fetal growth restriction. In conclusion, we did not find an association between TLR4 Asp299Gly and Thr399Ile gene polymorphisms and preeclampsia. As the Thr399Ile polymorphism is a highly informative tag SNP of the TLR4 gene, our results suggest that variations in this genomic region are not associated with preeclampsia. Nevertheless, further studies are required with determination of fetal TLR4 genotypes to explore the role of TLR4 gene polymorphisms in the risk of preeclampsia, especially in ethnically different populations.     

Toll-Like Receptor 2 Gene Polymorphisms Arg677Trp and Arg753Gln in Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is a leading cause of death worldwide, with a continually rising mortality rate. As COPD is driven by abnormal pulmonary and systemic inflammation, Toll-like receptors (TLRs) seem to be important. TLRs play a key role in innate response, and in particular TLR2 gene polymorphisms Arg677Trp and Arg753Gln have been linked to an increased risk of infection. The purpose of this study was to investigate whether there is a link between polymorphisms in TLR2 and the onset or course of COPD. We analyzed 149 Caucasian COPD patients and 150 healthy individuals by using polymerase chain reaction (PCR) followed by restriction fragment length polymorphism (RFLP) analysis. To further characterize the disease, patients were classified according to GOLD and divided into two subgroups comprising a stable (60/149) course and an unstable (89/149) course. The TLR2 Arg677Trp mutant allele was not found in any of the subjects. With a prevalence of 8.72% (13/149) for TLR2 Arg753Gln, the patients did not differ from the controls, with a prevalence of 10.67% (16/150). No significant difference was apparent (P = 0.571). None of the individuals showed homozygosity for TLR2 Arg753Gln. With regard to the course of COPD, the prevalence of TLR2 Arg753Gln in the control group did not differ significantly either from the stable subgroup (P = 0.196) or from the unstable subgroup (P = 0.891). Our results suggest that there is no association of the TLR2 polymorphisms Arg677Trp and Arg753Gln with either the onset or the course of COPD.     

Relevance of mutations in the TLR4 receptor in patients with gram-negative septic shock

BACKGROUND: Septic shock remains a significant health concern worldwide, and despite progress in understanding the physiological and molecular basis of septic shock, the high mortality rate of patients with septic shock remains unchanged. We recently identified a common polymorphism in toll-like receptor 4 (TLR4) that is associated with hyporesponsiveness to inhaled endotoxin or lipopolysaccharide in humans. METHODS: Since TLR4 is a major receptor for lipopolysaccharide in mammals and gram-negative bacteria are the prevalent pathogen associated with septic shock, we investigated whether these specific TLR4 alleles are associated with a predisposition to a more severe disease outcome for patients with septic shock. We genotyped 91 patients with septic shock as well as 73 healthy blood donor controls for the presence of the TLR4 Asp299Gly and TLR4 Thr399Ile mutations. RESULTS: We found the TLR4 Asp299Gly allele exclusively in patients with septic shock (P =.05). Furthermore, patients with septic shock with the TLR4 Asp299Gly/Thr399Ile alleles had a higher prevalence of gram-negative infections. CONCLUSION: Mutations in the TLR4 receptor may predispose people to develop septic shock with gram-negative microorganisms.     

Toll-like receptor 4 polymorphisms in dengue virus-infected children

Differential viral recognition by cells bearing Toll-like receptor 4 (TLR4) polymorphisms Asp299Gly and Thr399Ile may influence susceptibility and severity of dengue virus infection. In central Java, Indonesia, we investigated 201 children with dengue hemorrhagic fever (DHF) and 179 healthy controls. Patients and controls were mostly ethnic Javanese. A nearly complete cosegregation of the two mutations was observed. The TLR4 299/399 genotype was found in five patients and four controls. Prevalence of the TLR4 299/399 genotype did not differ significantly between controls and DHF patients or between patients with different severities of DHF. Also, vascular leakage in patients with different TLR4 genotypes did not differ. Thus, the 299/399 TLR4 haplotype has only minor influence on susceptibility and severity of complicated dengue virus infection.     

TLR4 mutations (Asp299Gly and Thr399Ile) are not associated with ankylosing spondylitis

BACKGROUND: Immunoregulatory genes and Gram negative gut bacteria are thought to be important in disease expression in ankylosing spondylitis (AS). OBJECTIVE: To compare the frequency of two common and functional TLR4 mutations (Asp299Gly, and Thr399Ile) between patients with AS and HLA-B27 healthy controls. METHODS: The TLR4 genotypes of patients and healthy HLA-B27 controls were determined using allele-specific PCR and restriction fragment length polymorphism analysis. Asp299Gly genotype was determined in 193 patients and 125 HLA-B27 positive controls and Thr399Ile genotype in 184 patients and 113 HLA-B27 controls. Allele frequencies were compared using a chi(2) test of association. RESULTS: 29/193 (15%) patients with AS had a polymorphism in the Asp299 site compared with 18/125 (14.4%) healthy HLA-B27 controls. Of the patients genotyped for the Thr399Ile allele, 29/184 (15.8%) carried the polymorphism compared with 19/113 (16.8%) HLA-B27 controls. No significant difference between the frequencies of the Asp299Gly genotype or the Thr399Ile genotype between patients with AS and healthy HLA-B27 controls was found. No significant difference in allele frequency was found at either site. CONCLUSION: Two common TLR4 polymorphisms, which cause a functional deficiency in host immune response to Gram negative bacteria, are not overrepresented in patients with AS.     

Analysis of single nucleotide polymorphisms in Toll-like receptor 4 shows no association with ankylosing spondylitis in a Korean population

The role of microbial triggers in the pathogenesis of the ankylosing spondylitis (AS) has remained an active area of clinical and basic research but remains unresolved. We have recently found evidence of an important role for TLR4 in experimental reactive arthritis, raising the question to be addressed whether genetic polymorphisms in TLR4 affects susceptibility to AS. Innate immune responses to Gram-negative bacteria involve in a central role the binding of lipopolysaccharide to TLR4. Two commonly occurring SNPs in the human TLR4 gene (Asp299Gly and Thr399Ile) have been shown to be associated with increased risk of Gram-negative bacteremia in sepsis patients and with susceptibility to inflammatory bowel disease. It remains unresolved whether these SNPs are associated with AS and we have addressed this in a relatively genetically homogeneous population in Korea. A cohort of 200 Korean AS patients and 197 ethnically matched controls were studied. All patients were native Koreans with AS satisfying the modified New York criteria. Korean controls were examined and confirmed to be unaffected by AS. All subjects were genotyped for two functional SNPs in the TLR4 gene: Asp299Gly (A/G polymorphism) and TLR-4 (Thr399Ile) (C/T polymorphism) The Sequenom MassARRAY system was used for genotyping (Sequenom Inc., San Diego, CA, USA). All cases and controls were homozygous for the (A) allele for 299 variant and similarly for the 399 variant all cases and controls were homozygous for the (C) allele. Genetic-environmental interactions figure prominently in current concepts of the pathogenesis of AS. Our findings indicate that the polymorphisms in the TLR4 gene cannot be regarded as major contributors to AS susceptibility in the Korean population.     

Lack of genetic association of the Toll-like receptor 4 (TLR4) Asp299Gly and Thr399Ile polymorphisms with spondylarthropathies in a Hungarian population

OBJECTIVES: Bacteria have long been suggested as aetiological factors in the genetically susceptible host in spondylarthropathies, including ankylosing spondylitis (AS) and reactive arthritis (ReA). Variability of the Toll-like receptor 4 (TLR4) gene has been shown to play a role in the inflammatory response to certain bacterial infections. We investigated whether TLR4 Asp299Gly and Thr399Ile polymorphisms contribute to the genetic background of spondylarthropathies in a cohort of Hungarian patients with AS and ReA. METHODS: DNA was obtained from patients with AS (n=138), ReA (n=91) and ethnically matched healthy controls (n=140). Genotyping was carried out by polymerase chain reaction-restriction fragment length polymorphism analysis and the results were confirmed by direct sequencing. RESULTS: No significant differences in allele or genotype frequencies were observed between controls and either the AS patients or the ReA patients. Clinical characteristics of these groups were unrelated to the presence of any of these polymorphisms. CONCLUSIONS: Toll-like receptor 4 Asp299Gly and Thr399Ile polymorphisms do not contribute to disease susceptibility in either AS or ReA. Functional abnormalities of the TLR4 signalling pathway suggested in spondylarthropathies seem not to be genetically determined by these two common polymorphisms.     

TLR4 polymorphisms, infectious diseases, and evolutionary pressure during migration of modern humans

Infectious diseases exert a constant evolutionary pressure on the genetic makeup of our innate immune system. Polymorphisms in Toll-like receptor 4 (TLR4) have been related to susceptibility to Gram-negative infections and septic shock. Here we show that two polymorphisms of TLR4, Asp299Gly and Thr399Ile, have unique distributions in populations from Africa, Asia, and Europe. Genetic and functional studies are compatible with a model in which the nonsynonymous polymorphism Asp299Gly has evolved as a protective allele against malaria, explaining its high prevalence in subSaharan Africa. However, the same allele could have been disadvantageous after migration of modern humans into Eurasia, putatively because of increased susceptibility to severe bacterial infections. In contrast, the Asp299Gly allele, when present in cosegregation with Thr399Ile to form the Asp299Gly/Thr399Ile haplotype, shows selective neutrality. Polymorphisms in TLR4 exemplify how the interaction between our innate immune system and the infectious pressures in particular environments may have shaped the genetic variations and function of our immune system during the out-of-Africa migration of modern humans.