3′UTR C2370A allele of the IL-23 receptor gene is associated with relapsing-remitting multiple sclerosis

Association of IL17 and IL23R gene polymorphisms with rheumatic heart disease in South Indian population

BACKGROUND

IL-23/Th17 signaling pathway plays a crucial role in the cell-mediated immune response against bacterial infections and also in the pathogenesis of inflammatory and autoimmune diseases. Recent studies indicate that Th17 cell-associated cytokines are involved in the progression and maintenance of valvular lesions in rheumatic heart disease (RHD). Variants in the genes of cytokines that are potentially involved in Th17 response may influence interindividual differences in their expression levels, thereby contributing to the pathogenesis of immune-mediated diseases such as RHD.

OBJECTIVE

The aim of the study is to investigate the association of IL17A, IL17F, and IL23R gene variants with the risk perception of RHD.

METHODS

A total of 225 individuals (99 RHD patients and 126 healthy siblings) were recruited for the study. The IL17A (rs2275913), IL17F (rs763780), and IL23R (rs10889677) polymorphisms were determined by polymerase chain reaction restriction fragment length polymorphisms and amplification-refractory mutation system-polymerase chain reaction methods, respectively.

RESULTS

The frequency of IL17A (rs2275913) A/A genotype was significantly high in pooled RHD patients (odds ratio [OR] = 2.76; p_c = 0.021), rheumatic fever (RF) patients (OR = 14.5; p_c = 0.0001), and mitral valvular lesions patients (OR = 2.74; p_c = 0.039) when compared to healthy siblings. However, the IL17F (rs763780) and IL23R (rs10889677) polymorphisms did not show any association with RHD.

CONCLUSIONS

The results suggest that IL17A (rs2275913) polymorphism is associated with the development of RF/RHD in South Indian population. Further studies are required to substantiate the association of these genes with the disease risk.

Characterization of variations in IL23A and IL23R genes: possible roles in multiple sclerosis and other neuroinflammatory demyelinating diseases

Multiple sclerosis is among the most serious inflammatory demyelinating diseases (IDD). Interleukin-23A (IL23A) regulates and coordinates the activities of immune cells by interacting with its receptor IL23R and plays key roles in the pathogenesis of immune inflammatory diseases. IDD, deemed to be a kind of autoimmune diseases, may involve IL23A in the pathogenesis. The aim of this work was to validate the hypothesized involvement of IL-23A and its receptor in IDD. We sequenced the IL-23A and IL-23R genes for 206 Chinese Han IDD patients and evaluated SNPs within or near those genes. The serum levels of IL23A in IDD participants were analyzed using ELISA. The statistical analyses were conducted using Chi-Square Tests as implemented in SPSS (version 19.0). The Hardy-Weinberg equilibrium test of the population was carried out using online software OEGE. Three variants rs2066808, rs2371494, rs11575248 in IL-23A gene and one variant rs1884444 in IL-23R gene were demonstrated to be associated with the risk of MS or other IDD diseases, and the expression level of serum IL-23A in the MS patients was also altered. We conclude that variants in IL-23A and IL-23R genes were associated with the risk of MS or other IDD diseases.

A blood-based biomarker panel indicates IL-10 and IL-12/23p40 are jointly associated as predictors of β-amyloid load in an AD cohort

Alzheimer’s Disease (AD) is the most common form of dementia, characterised by extracellular amyloid deposition as plaques and intracellular neurofibrillary tangles of tau protein. As no current clinical test can diagnose individuals at risk of developing AD, the aim of this project is to evaluate a blood-based biomarker panel to identify individuals who carry this risk. We analysed the levels of 22 biomarkers in clinically classified healthy controls (HC), mild cognitive impairment (MCI) and Alzheimer’s participants from the well characterised Australian Imaging, Biomarker and Lifestyle (AIBL) study of aging. High levels of IL-10 and IL-12/23p40 were significantly associated with amyloid deposition in HC, suggesting that these two biomarkers might be used to detect at risk individuals. Additionally, other biomarkers (Eotaxin-3, Leptin, PYY) exhibited altered levels in AD participants possessing the APOE ε4 allele. This suggests that the physiology of some potential biomarkers may be altered in AD due to the APOE ε4 allele, a major risk factor for AD. Taken together, these data highlight several potential biomarkers that can be used in a blood-based panel to allow earlier identification of individuals at risk of developing AD and/or early stage AD for which current therapies may be more beneficial.

Interleukin-23 receptor single nucleotide polymorphisms in ulcerative colitis. A study in Iranian populations

BACKGROUND/OBJECTIVE

Genetic factors seem to play an important role in the pathogenesis of ulcerative colitis (UC). Genome wide association studies showed a highly significant association between interleukin 23 receptor (IL23R) single nucleotide polymorphisms (SNPs) and Crohn's disease; however, there are contrary results regarding the disease-modifying effects of IL23R variants in UC. This study was performed in a group of patients with UC to test the possible role of IL23R SNPs in conferring susceptibility or protection against the disease.

METHODS

The study was performed on 67 Iranian adult patients with UC and 78 healthy controls. Eight IL23R SNPs were genotyped, using real-time polymerase chain reaction (RT-PCR). The frequencies of alleles and genotype at each position were determined and compared between two groups of patients and controls.

RESULTS

The frequency of the T allele at position rs1343151 was significantly higher in the patient group, compared to the controls (P=0.018). The TT genotype at the same position was also significantly overrepresented in the patient group (P=0.02). There was no significant difference in alleles and genotype frequencies of other SNPs between patients and controls.

CONCLUSIONS

This study identified a new susceptibility locus associated with UC. Our findings provide further insight into the genetics of UC, which might be amenable to future therapeutic intervention.

Association of IL-23 and its receptor gene single-nucleotide polymorphisms with multiple sclerosis in Chinese southern population

The subunit of IL-23 (IL12B) and its receptor (IL23R) gene single-nucleotide polymorphisms (SNPs) have been shown to be associated with several autoimmune diseases such as inflammatory bowel disease, psoriasis and ankylosing spondylitis. However, the association studies between multiple sclerosis (MS) and SNPs of IL12B or IL23R gene have been reported with inconsistent results in Caucasian population. These discrepancies prompted us to investigate whether IL12B and IL23R variants are associated with susceptibility to MS in Chinese southern population. In this study, we investigated four SNPs (rs2201841, rs10889677, rs7517847 in IL23R and rs3212227 in IL12B) in 178 MS patients and 221 health controls in southern China using the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method. There was no difference of genotype or allele distribution of these SNPs between MS patients and controls. No association was found between gene polymorphisms and clinical characteristics in MS patients. Furthermore, haplotypes analysis showed similar distribution of haplotype frequencies in MS patients and controls. Our study showed that the IL12B and IL23R gene SNPs does not seem to be associated with MS susceptibility in Chinese southern population.

Inflammatory bowel disease and demyelination: more than just a coincidence?

Infliximab and other anti-TNF-α agents have been implicated for drug-induced demyelination in patients with inflammatory bowel diseases (IBDs). We evaluated existing data from MEDLINE and EMBASE and conducted a narrative review to investigate further the aforementioned association. Our literature search highlighted 34 case reports, 3 case-control studies, 1 prospective and 7 retrospective cohort studies published in English. Available data suggest that IBD patients can manifest demyelinating events in both central and peripheral nervous system, however, they are still insufficient to conclude whether anti-TNF-α therapies are an independent risk factor for demyelination. Prospective cohort studies with internal control groups are needed to estimate the true incidence of demyelinating disorders in patients with IBD and to elucidate if anti-TNF-α therapy increases further the risk of demyelination.

Significant association between IL23R and IL17F polymorphisms and clinical features of colorectal cancer

Th17cells are involved in inflammatory and autoimmune diseases. These cells may be involved in pathological processes mainly producing pro-inflammatory cytokines. Recently, it was shown that the IL23/IL17 pathway plays an important role in the development of inflammatory bowel disease. In general, genes encoding cytokines are genetically polymorphic and polymorphisms in genes IL23R el IL17F were shown associated with susceptibility to Crohn's disease and ulcerative colitis which in their turn are considered as risk factors for developing colorectal cancer (CRC). Our approach is to study IL17F and IL23R polymorphisms as risk factor associated with CRC in the Tunisian population in patients and healthy controls. Interesting, we noted a significant association between IL17F and IL23R polymorphisms and tumor location (p=0.0001 and p=0.049, respectively), tumor histology (p=0.007 and p=0.049, respectively) and tumor architecture (p=0.0000000001 and p=0.07, respectively) in CRC patients. We also showed a significant association of IL17F variant with an increased risk of TNM stage III/IV (p=0.007), showing an increased risk of advanced stage. Finally, we observed a positive link between IL17F polymorphism and CRC patients with lymph nodes (p=0.0000000001) and metastasis (p=0.00000009). However, we found no evidence to support a significant association between IL17F and IL23R polymorphisms and colorectal cancer susceptibility. Our findings suggest that IL17F and IL23R polymorphisms were significantly associated with clinical features variables. The IL17F cytokine appear to be involved in the control of tumor growth and invasion of gastrointestinal tumors. IL17 and IL23 polymorphisms or those of their receptors as important determinants of susceptibility to colorectal cancer are still subject to questioning.

Lentivirus-mediated estrogen receptor α overexpression in the central nervous system ameliorates experimental autoimmune encephalomyelitis in mice

Multiple sclerosis (MS) is an autoimmune disease characterized by inflammatory cell infiltration of the central nervous system (CNS) and multifocal demyelination. Clinical data and clinical indicators demonstrate that estrogen improves the relapse-remittance of MS patients. This study aimed to investigate the anti-inflammatory effects and the underlying mechanism(s) of action of estrogen and estrogen receptor α (ERα) in an experimental autoimmune encephalomyelitis (EAE) mouse model of MS. An ERα recombinant lentivirus was constructed. Mouse neurons were cultured in serum-free culture medium, and ERα recombinant lentivirus with a multiplicity of infection (MOI) of 5 was used to infect the neurons. Furthermore, neuronal ERα mRNA and protein expression were detected using real-time quantitative PCR and western blot analysis. We sterotaxically injected ERα recombinant lentivirus into the lateral ventricle of mouse brains, and successfully identified infected neurons using Flag immunofluorescence staining to determine the optimal dose. A total of 75 C57BL/6 mice were ovariectomized. After 2 weeks, EAE was induced with myelin oligodendrocyte glycoprotein (MOG) 35-55 peptide. The EAE mice were divided into 5 groups: the estrogen group (treatment with estradiol), the ERα agonist group (treatment with raloxifene), the ERα recombinant lentivirus group (ERα group, treatment with ERα recombinant lentivirus), the empty virus group and the normal saline (NS) group; clinical symptoms and body weight were compared among the groups. We assessed EAE-related parameters, detected pathological changes with immunohistochemistry and quantified the expression of myelin basic protein (MBP), matrix metalloproteinase-9 (MMP-9), and a subset of EAE-related cytokines using enzyme-linked immunosorbent assay (ELISA). We successfully constructed an ERα recombinant lentivirus. C57BL/6 mouse neurons can survive in culture for at least 8 weeks. During that period, the recombinant lentivirus was able to infect the neurons, while sustaining green fluorescence protein (GFP) expression. ERα recombinant lentivirus also infected the neurons at a MOI of 5. The ERα mRNA and protein expression levels were higher in the infected neurons compared to the uninfected ones. We successfully infected the CNS of C57BL/6 mice by stereotaxically injecting ERα recombinant lentivirus into the lateral ventricle of the mouse brains and induced EAE. The lentivirus-mediated overexpression of ERα reduced the incidence of EAE, ameliorated the clinical symptoms, inhibited inflammatory cell CNS infiltration, and reduced nerve fiber demyelination. MMP-9, tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ), interleukin (IL)-17 and IL-23 expression levels were decreased, while those of MBP and IL-4 were increased. These data demonstrate that it is possible to induce the overexpression of ERα using a recombinant lentivirus, and that this novel intervention ameliorates EAE in a mouse model. Mechanistically, estrogen and ERα inhibit inflammatory responses, and ERα alleviates damage to the myelin sheath. Collectively, our findings support the potential use of ERα as a therapeutic target for the treatment of MS.

Increased activity of interleukin-23/interleukin-17 cytokine axis in primary antiphospholipid syndrome

The aim of the study was to investigate serum concentrations of interleukin (IL)-17 and IL-17-inducing cytokines IL-23 and transforming growth factor (TGF)-β, as well as IL-17 single nucleotide polymorphism (SNP) rs2275913 in patients with primary antiphospholipid syndrome (PAPS). We studied fifty patients with PAPS and fifty age- and sex-matched healthy controls. The cytokine levels were measured by ELISA, while the rs2275913 SNP located in promoter region of IL-17 gene was genotyped using real-time PCR. The significantly higher levels of IL-17 (p=0.002), IL-23 (p<0.001) and TGF-β (p=0.042) were found in PAPS patients (median 13.1, 9.4, and 125.6 pg/ml, respectively) compared to the control group (6.8, 4.9 and 44.4 pg/ml). There was a significant positive correlation between concentrations of IL-17 and IL-23 (r=0.540, p<0.001), but not between those of IL-17 and TGF-β. No statistically significant differences were observed in the distribution of genotypes and alleles of the IL-17 rs2275913 variants in patients with PAPS compared to healthy subjects. The blood concentrations of IL-17 did not differ in subjects with different rs2275913 genotypes or patients with or without antiphospholipid antibodies. Finally, a trend toward higher IL-17 levels (p=0.063) and the significantly higher IL-17 concentrations (p=0.012) were observed in PAPS patients with deep vein thrombosis and thrombocytopenia, respectively. These data demonstrate that IL-23/IL-17 axis, stimulated independently of TGF-β increase IL-17A gene polymorphism and antiphospholipid antibody production, might contribute to vascular manifestations of PAPS.

Cytokine gene polymorphisms and human autoimmune disease in the era of genome-wide association studies

Cytokine (receptor) genes have traditionally attracted great interest as plausible genetic risk factors for autoimmune disease. Since 2007, the implementation of genome-wide association studies has facilitated the robust identification of allelic variants in more than 35 cytokine loci as susceptibility factors for a wide variety of over 15 autoimmune disorders. In this review, we catalog the gene loci of interleukin, chemokine, and tumor necrosis factor receptor superfamily and ligands that have emerged as autoimmune risk factors. We examine recent progress made in the clarification of the functional mechanisms by which polymorphisms in the genes coding for interleukin-2 receptor alpha (IL2RA), IL7R, and IL23R may alter risk for autoimmune disease, and discuss opposite autoimmune risk alleles found, among others, at the IL10 locus.

Association of IL-12B genetic polymorphism with the susceptibility and disease severity of ankylosing spondylitis

OBJECTIVE

Interleukin 23 (IL-23) stimulates the differentiation of T helper 17 (Th17) cells, which are involved in the pathogenesis of ankylosing spondylitis (AS). Binding of IL-23 to the IL-23 receptor complex activates Janus kinases 2 and tyrosine kinase 2, which phosphorylate IL-23R and subsequently promote the transcription of the IL-17 gene. IL-12B encodes a p40 subunit common to IL-12 and IL-23. We evaluated the effects of IL-12B and IL-23R genotype on the occurrence and clinical features of AS.

METHODS

A total of 362 patients with AS and 362 healthy controls were enrolled in the study. Genotypes of IL-12B A1188C (rs3212227) and IL-23R C2370A (rs10889677) were identified by polymerase chain reaction/restriction fragment-length polymorphism. Disease activity and functional status were assessed by Bath AS indices.

RESULTS

Subjects carrying IL-12B CC [matched relative risk (RR(m)) 1.93, 95% CI 1.23-3.03] and IL-12B AC (RR(m) 1.73, 95% CI 1.21-2.46) genotypes had a significantly greater risk of developing AS than subjects with the IL-12B AA genotype. Subjects carrying both IL-12B CC and IL-23R AA genotypes also had a significantly higher risk (RR(m) 2.98, 95% CI 1.51-5.89) of developing AS compared to those with IL-12B AA and IL-23R CC/CA genotypes, and this interaction between IL-12B and IL-23R was significant. Patients with AS who had IL-12B CC and IL-12B AC genotypes had an obviously increased Bath Ankylosing Spondylitis Disease Activity Index score compared to those who carried the IL-12B AA genotype (4.3 vs 3.7).

CONCLUSION

The IL-12B A1188C genotype was associated with the development and disease severity of AS.

IL-23 in infections, inflammation, autoimmunity and cancer: possible role in HIV-1 and AIDS

The growing family of interleukin (IL)-12-like cytokines produced by activated macrophages and dendritic cells became the important players in the control of infections, development of inflammation, autoimmunity and cancer. However, the role of one of them-heterodimer IL-23, which consists of IL12p40 and the unique p19 subunit in HIV-1 infection pathogenesis and progression to AIDS, represent special interest. We overviewed findings of IL-23 involvement in control of peripheral bacterial pathogens and opportunistic infection, central nervous system (CNS) viral infections and autoimmune disorders, and tumorogenesis, which potentially could be applicable to HIV-1 and AIDS.

Interleukin-23 receptor polymorphism as a risk factor for oral cancer susceptibility

BACKGROUND

The purpose of this study was to evaluate the influence of genetic polymorphisms of interleukin (IL)-23 and the IL-23 receptor (IL-23R) on the susceptibility to oral cancer.

METHODS

Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was used to measure polymorphisms of these genes in 240 controls and 240 patients with oral cancer.

RESULTS

Individuals with at least 1 varied C allele of rs10889677 (IL-23R polymorphism) had a 1.553-fold risk (95% confidence interval [CI], 1.073-2.241) of developing oral cancer compared with patients with the wild-type A/A homozygote. Patients with oral cancer with at least 1 varied C allele of rs10889677 had a 1.931-fold risk of tumor lymph node metastasis compared with patients with the C/C homozygote.

CONCLUSION

The varied C allele of the IL-23R gene may be considered a factor contributing to increased susceptibility and may be a predictive factor for tumor lymph node metastasis in Taiwanese with oral cancer.

Current perspectives on the role of IL-17 in autoimmune disease

Until recently, autoimmune diseases had been categorized as either Th1- or Th2-mediated diseases. However, the discovery of a novel subset of helper T cells producing interleukin (IL)-17, ie, Th17 cells, changed this paradigm. Currently, IL-17 and Th17 cells are implicated in many autoimmune diseases, such as rheumatoid arthritis, psoriasis, multiple sclerosis, and inflammatory bowel diseases. Such conclusions were initially drawn from observations in animal models of autoimmune diseases, and accumulating data from clinical research also support the involvement of IL-17 in human diseases as well. Reagents targeting Th17-related molecules have been under clinical investigation for some diseases but have not always been effective in controlling disease activity. Consistent with this, it has become evident that there are substantial differences in the development of Th17 cells and in the way they function in autoimmune diseases between humans and experimental animals. Thus, further investigation is needed before we can draw any conclusions about the importance of IL-17 and Th17 cells in human autoimmune diseases.

Association of interleukin-23 receptor gene polymorphisms with risk of ovarian cancer

Among gynecological malignancies, ovarian cancer is the leading cause of death. The overall 5-year survival rate remains poor, and the pathogenesis is unknown. The interleukin-23 receptor (IL23R) is known to be critically involved in the carcinogenesis of different malignant tumors. To assess the role of IL23R in ovarian cancer, we conducted a study to investigate the polymorphisms of the IL23R gene in 96 Han Chinese women with histologically proven ovarian cancer. Polymerase chain reaction-restriction fragment length polymorphism was used for genotyping. In all three single nucleotide polymorphisms of IL23R studied, the distribution of genotype and allele frequencies of rs10889677 differed significantly between patients and controls. The frequency of allele C of rs10889677 was significantly increased in cases compared with controls (0.281 vs. 0.183, odds ratio OR=1.752, 95% confidence interval CI=1.107-2.772). Furthermore, when stratified by tumor stage, we found that the allele frequencies of rs11465817 differed significantly between FIGO stage I+II and III+IV. The higher frequency of allele A was significantly associated with advanced ovarian cancer (P=0.027, OR=2.087, 95% CI=1.083-4.023). These findings indicate that IL23R polymorphisms may play an important role in the susceptibility and prognosis of ovarian cancer in the Chinese population.

Immunological basis for the development of tissue inflammation and organ-specific autoimmunity in animal models of multiple sclerosis

Experimental autoimmune encephalomyelitis (EAE) is an animal model for multiple sclerosis (MS) that has shaped our understanding of autoimmune tissue inflammation in the central nervous system (CNS). Major therapeutic approaches to MS have been first validated in EAE. Nevertheless, EAE in all its modifications is not able to recapitulate the full range of clinical and histopathogenic aspects of MS. Furthermore, autoimmune reactions in EAE-prone rodent strains and MS patients may differ in terms of the relative involvement of various subsets of immune cells. However, the role of specific molecules that play a role in skewing the immune response towards pathogenic autoreactivity is very similar in mice and humans. Thus, in this chapter, we will focus on the identification of a novel subset of inflammatory T cells, called Th17 cells, in EAE and their interplay with other immune cells including protective regulatory T cells (T-regs). It is likely that the discovery of Th17 cells and their relationship with T-regs will change our understanding of organ-specific autoimmune diseases in the years to come.

The IL-23/Th17 axis in the immunopathogenesis of psoriasis

Abnormal production of inflammatory mediators is believed to play an important role in the pathogenesis of psoriasis. Emerging data, both in mice and in humans, put the spotlight on a new subset of T helper (Th) cells, in part characterized by their production of IL-17 and accordingly named Th17 cells. Here, we review the development, characterization, and function of human Th17 cells as well as the crucial role of IL-23 in the context of Th17-cell-dependent chronic inflammation in psoriasis. We further discuss recent clinical trials targeting the IL-23/Th17 axis in psoriasis.

Regulation and function of proinflammatory TH17 cells

Naïve CD4(+) helper T (TH) cells, upon activation by antigen-presenting cells (APC), differentiate into different types of effector cells that are characterized by their distinct cytokine production profiles and immune regulatory functions. In addition to TH1 and TH2 cells, a third subset of effector TH cells has recently been described and termed TH17. Since their identification, TH17 cells have emerged as crucial players in infectious, inflammatory, and autoimmune diseases, and cancer. In this review, we summarize the latest discoveries on the cytokine-mediated regulation and transcriptional programming of TH17 cells and their roles in different immune responses and diseases.

Identification and characterization of multiple splice forms of the human interleukin-23 receptor alpha chain in mitogen-activated leukocytes

The signalling of interleukin-23 (IL-23) and its receptor (IL-23R) is a key element in the differentiation of T cells to the Th17 phenotype. Here, we present the identification and characterization of human IL23R splice variants resulting from alternative splicing of the IL23R mRNA, from activated human leukocytes, following the analysis of IL23R cDNA. Twenty-four different IL23R transcripts were observed in this study, which may potentially lead to an alteration in the protein coding region of IL-23R alpha. Consequently, by analysing amino acid sequences deduced from alternatively spliced mRNA sequences, four different putative premature early termination forms of IL-23R alpha: (1) a very short 'IL-23R alpha', (2) an IL-23R alpha containing only the extracellular region, (3) a IL-23R alpha with truncated intracellular domain and (4) in-frame exon-skipping causing changes to the extracellular region of the IL-23R alpha were revealed. These changes may affect the function of IL-23R by altering the ligand-binding interaction, producing a soluble form of the receptor to act as a decoy receptor and/or modify the IL-23/IL-23R signalling, respectively. Taken together, identification of potentially functional splice variants of IL23R underscores the biological diversity of the IL23R gene and will aid in the understanding of the gene's function in normal and pathological conditions.

Detailed genetic characterization of the interleukin-23 receptor in psoriasis

Using a multi-tiered, case-control association design, scanning 25 215 gene-centric SNPs, we previously identified two psoriasis susceptibility genes: IL12B and IL23R. These results have recently been confirmed. To better characterize the IL23R psoriasis-association, we used a fine mapping strategy to identify 59 additional IL23R-linked SNPs, which were genotyped in our three independent, white North American sample sets (>2800 individuals in toto). A sliding window of haplotype association demonstrates colocalization of psoriasis susceptibility effects within the boundaries of IL23R across all sample sets, thereby decreasing the likelihood that neighboring genes, particularly IL12RB2, are driving the association at this region. Additional haplotype work identified two 5-SNP haplotypes with strong protective effects, consistent across our three sample sets (OR(common)=0.67; P(comb)=4.32E-07). Importantly, heterogeneity of effect was extremely low between sample sets for these haplotypes (P(Het)=0.961). Together, these protective haplotypes attain a frequency of 16% in controls, declining to 11% in cases. The characterization of association patterns within IL23R to specific predisposing/protective variants will play an important role in the elucidation of psoriasis etiology and other related phenotypes. Further, this work is essential to lay the foundation for the role of IL23R genetics in response to pharmaceutical therapy and dosage.

Th17 cell differentiation: the long and winding road

The characterization of the new lineage of IL-17-producing CD4+ T helper (Th17) cells has revolutionized our current understanding of T cell-mediated immunity. Over the past five years, there have been many twists and turns as the pathways that lead to Th17 cell differentiation have been elucidated. Not least of these was the discovery that TGF-beta is a crucial cytokine for Th17 cell development, suggesting that Th17 and regulatory T cell subsets share reciprocal developmental pathways during the pathogenesis or control of inflammation. This review aims to bring together the observations that have formed current opinion on factors that promote and contain Th17 cell development, in both mouse and man. Unresolved controversies in this field are also discussed: For example, IL-23 is absolutely required for disease pathogenesis in many models of Th17-cell-mediated autoimmunity, yet its role in Th17 cell development is relatively unclear.