IL-7-enhanced T-cell response to myelin proteins in multiple sclerosis

Antisense modulation of IL7R splicing to control sIL7R expression in human CD4+ T cells

The interleukin 7 receptor (IL7R) is strongly associated with increased risk to develop multiple sclerosis (MS), an autoimmune disease of the central nervous system, and this association is likely driven by up-regulation of the soluble isoform of IL7R (sIL7R). Expression of sIL7R is determined by exclusion of the alternative exon 6 from IL7R transcripts, and our previous work revealed that the MS risk allele of the SNP rs6897932 within this exon enhances the expression of sIL7R by promoting exclusion of exon 6. sIL7R potentiates the activity of IL7, leading to enhanced expansion of T cells and increased disability in the experimental autoimmune encephalomyelitis (EAE) murine model of MS. This role in modulating T cell-driven immunity positions sIL7R as an attractive therapeutic target whose expression could be reduced for treatment of MS or increased for treatment of cancers. In this study, we identified novel antisense oligonucleotides (ASOs) that effectively control the inclusion (anti-sIL7R ASOs) or exclusion (pro-sIL7R ASOs) of this exon in a dose-dependent fashion. These ASOs provided excellent control of exon 6 splicing and sIL7R secretion in human primary CD4⁺ T cells. Supporting their potential for therapeutic targeting, we showed that lead anti-sIL7R ASOs correct the enhanced exon 6 exclusion imposed by the MS risk allele of rs6897932, whereas lead pro-sIL7R ASOs phenocopy it. The data presented here form the foundation for future preclinical studies that will test the therapeutic potential of these ASOs in MS and immuno-oncology.

Association between IL7 Receptor Alpha (Il7ra) gene rs6897932 polymorphism and the risk of Multiple Sclerosis: A meta-regression and meta-analysis

BACKGROUND

In this systematic review and meta-analysis, we aimed to find a consistent conclusion for the association between the interleukin 7 receptor alpha (IL7RA) gene rs6897932 single nucleotide polymorphism (SNP) and multiple sclerosis (MS) risk.

METHODS

Here, we performed a comprehensive systematic search in PubMed, Scopus, and Web of Science to find relevant studies published before November 2020 investigating the association between rs6897932 SNP and MS risk. In the pooled analysis, we determined the odds ratio (OR) and the corresponding 95% confidence interval (CI) for the association level between rs6897932 SNP and the risk of MS.

RESULTS

In the current meta-analysis 33 case-control studies (30 articles) containing 19351 patients and 21005 healthy controls certify the inclusion criteria. According to the pooled analysis, a statistically significant association of IL7RA gene rs6897932 SNP with MS risk was found across recessive model (OR= 0.84, 95% CI= 0.77-0.92, P< 0.001, FEM), allelic model (OR= 0.91, 95% CI= 0.85-0.99, P= 0. 02, REM), TT vs. CC model (OR= 0.79, 95% CI= 0.67-0.93, P= 0.005, REM). Moreover, the subgroup analysis based on the ethnicity indicated a negative significant association in Europeans; dominant model (OR= 0.88, 95% CI= 0.78-1.01, P= 0.06, REM), recessive model (OR= 0.79, 95% CI= 0.71-0.88, P< 0.001, REM), allelic model (OR= 0.88, 95% CI= 0.81-0.96, P= 0.003, REM), TT vs. CC model (OR= 0.74, 95% CI= 0.61-0.88, P<0.001, REM) models. Nonetheless, no significant association was detected in Asians and Americans.

CONCLUSIONS

IL7RA gene rs6897932 SNP decreases MS susceptibility in overall population and Europeans.

Deleterious and Oncogenic Mutations in the IL7RA

Interleukin 7 (IL-7) is a critical cytokine that plays a fundamental role in B- and T-cell development and in acute lymphoblastic leukemia (ALL). Its receptor (IL7R) is a transmembrane heterodimer formed by the IL7Rα and the IL2Rγ chain (γc). The IL7R signals through the JAK/STAT pathway. Loss-of-function mutations and some polymorphisms of the IL7Rα were associated to immunodeficiency and inflammatory diseases, respectively. Gain-of-function mutations were described in T-cell ALL and in high risk precursor B-cell ALL. Most confirmed loss-of-function mutations occur in the extracellular part of the IL7Rα while oncogenic mutations are exclusively found in the extracellular juxtamembrane (EJM) or transmembrane regions. Oncogenic mutations promote either IL7Rα/IL7Rα homodimerization and constitutive signaling, or increased affinity to γc or IL-7. This work presents a review on IL7Rα polymorphisms/mutations and attempts to present a classification based on their structural consequences and resulting biological activity.

Association of interleukin 6, interleukin 7 receptor alpha, and interleukin 12B gene polymorphisms with multiple sclerosis

Pro-inflammatory and anti-inflammatory cytokines have been shown to play a crucial role in the pathophysiology of multiple sclerosis (MS). We investigated the association between interleukin (IL) IL6-174 G/C (rs1800795), IL7RA C/T (rs6897932), and IL-12B A1188C (rs3212227) gene polymorphisms (SNPs) and MS. The study consisted of 297 unrelated MS patients and 135 healthy individuals. In IL6-174G/C (rs1800795), a significant association between the C allele and MS risk [OR 1.41, 95% CI (1.05-1.92); P = 0.025] was found. Carriage of genotypes CC and CG were more common in MS patients [OR 1.58, 95% CI (1.04-2.39); P = 0.031] and also in female MS patients [OR 1.68, 95% CI (1.02-2.79); P = 0.043]. However, after applying Bonferroni's correction the differences did not remain significant. No significant association between the IL7RA C/T (rs6897932) and IL12B A1188C (rs3212227) gene polymorphisms and MS susceptibility was observed. Regarding IL-12B A1188C (rs3212227), a significant association between the CC genotype and MS progression, expressed as MSSS, was demonstrated in the female MS group. Our results indicate that the distribution of IL6-174G/C (rs1800795) SNP was marginally associated with MS susceptibility. We also showed that IL-12B A1188C (rs3212227) can contribute to the progression of the disease in the Czech population.

Variants of Interleukin-7/Interleukin-7 Receptor Alpha are Associated with Both Neuromyelitis Optica and Multiple Sclerosis Among Chinese Han Population in Southeastern China

BACKGROUND

Neuromyelitis optica (NMO) and multiple sclerosis (MS) are autoimmune demyelinating diseases of the central nerve system. Interleukin-7 (IL-7) and interleukin-7 receptor alpha (IL-7Rα) were proved to be important in the pathogenesis of both diseases because of the roles they played in the differentiations of autoimmune lymphocytes. The variants of both genes had been identified to be associated with MS susceptibility in Caucasian, Japanese and Korean populations. However, the association of these variants with NMO and MS has not been well studied in Chinese Southeastern Han population. Here, we aimed to evaluate the association of six IL-7 variants (rs1520333, rs1545298, rs4739140, rs6993386, rs7816065, and rs2887502) and one variant of IL-7RA (rs6897932) with NMO and MS among Chinese Han population in southeastern China.

METHODS

Matrix-assisted laser desorption/ionization time of flight mass spectrometry (MassARRAY system) and Sanger sequencing were used to determine the variants of IL-7 and IL-7RA in 167 NMO patients, 159 MS patients and 479 healthy controls among Chinese Han population in southeastern China. Samples were excluded if the genotyping success rate <90%.

RESULTS

Statistical differences were observed in the genotypes of IL-7 rs1520333 in MS patients and IL-7RA rs6897932 in NMO patients, compared with healthy controls (P = 0.035 and 0.034, respectively). There was a statistically significant difference in the genotypes of IL-7 rs2887502 between MS and NMO patients (P = 0.014). And there were statistically significant differences in the rs6897932 genotypes (P = 0.004) and alleles (P = 0.042) between NMO-IgG positive patients and healthy controls.

CONCLUSIONS

The study suggested that among Chinese Han population in southeastern China, the variant of IL-7RA (rs6897932) was associated with NMO especially NMO-IgG positive patients while the variant of IL-7 (rs1520333) with MS patients. And the genotypic differences of IL-7 rs2887502 between MS and NMO indicated the different genetic backgrounds of these two diseases.

Interleukin 7 receptor polymorphisms and the risk of multiple sclerosis: A meta-analysis

BACKGROUND

Multiple sclerosis (MS) is considered as the most common chronic inflammatory neurologic disorder diagnosed in young adults. Both environmental and genetic factors may influence risk of MS development. Interleukin 7 receptor (IL7R) is one of the most studied gene polymorphism on MS that may play a possible role in MS development. The most studied polymorphism of IL7R gene is "rs6897932" polymorphism on IL7Rα gene (IL7RA).

METHODS

PubMed, Scopus, and Google scholar databases were searched for all of related studies on the association of IL7RA polymorphism with single nucleotide polymorphism (SNP) ID of "rs6897932" and the risk of MS through August 07, 2015. After exclusion of irrelevant articles, 11 eligible studies were selected, which were analyzed to determine an association between the MS and IL7R T244I polymorphism (rs6897932). For identification of this association, odds ratios (ORs) and 95% confidence interval (95% CI) were calculated. Four models of allelic (T vs. C), co-dominant genotype (TT vs. CC), dominant (TT+CT vs. CC), and recessive genotypes (TT vs. CT+CC) were considered to check the possible role of rs6897932 polymorphism in MS. A sensitivity analysis was conducted to find the reliability of this study. Furthermore, funnel plots were used to evaluate publication bias.

RESULTS

A total of 11 case-control studies were identified through this meta-analysis, which containing 6752 cases and 7349 controls. In overall, the frequency of the C allele was found to be higher in patients with MS compared to healthy controls (75.66% vs. 72.19%). T allele was significantly associated with the decreased risk of MS in a random effect model (T vs. C: OR=0.84, 95% CI=0.77-0.92, P-value <0.001). In the co-dominant, dominant, and recessive genotypes models, a significant association between the IL7R T244I polymorphism and MS risk was demonstrated (TT vs. CC: OR=0.70, 95% CI=0.61-0.80, P-value <0.001; TT+CT vs. CC: OR=0.82, 95% CI=0.73-0.92, P-value <0.001; TT vs. CT+CC: OR=0.76, 95% CI=0.66-0.87, P-value <0.001). Sensitivity analysis revealed that this study is reliable. There was no evidence of publication bias.

CONCLUSION

It was demonstrated that the IL7R T244I polymorphism was associated with susceptibility to MS. However, more well-designed studies with large sample size are needed to validate this association between this single nucleotide polymorphism and MS.

IL-7 induces clathrin-mediated endocytosis of CD127 and subsequent degradation by the proteasome in primary human CD8 T cells

Interleukin-7 (IL-7), a key immunoregulatory cytokine, plays an essential role in peripheral T-cell homeostasis and function. Signaling via the IL-7 receptor is tightly regulated and we and others have shown IL-7 provides negative feedback on its own signaling by downregulating expression of the IL-7 receptor alpha-chain (CD127) through both suppression of CD127 gene transcription and by internalization of existing CD127 proteins from the cell membrane. We show here for the first time in primary human CD8 T cells that upon stimulation with IL-7, CD127 is internalized through clathrin-coated pits, a process dependent on both lipid-raft formation and the activity of dynamin. As visualized by confocal microscopy, CD127 shows increased co-localization with clathrin within 5 min of IL-7 stimulation and within 15-30 min is seen in multiple intracellular punctae co-localizing with the early endosomal marker EEA1. By 2 h after addition of IL-7, CD127 staining associates with the late endosomal marker RAB7 and with the proteasomal 20S subunit. By inducing receptor internalization and translocation from early endosomes to the proteasome, IL-7 directly influences its receptor density on the cell surface and thus regulates the intensity of its own signaling cascades. Given the important role IL-7 plays in T-cell development, homeostasis and function, deciphering how expression of its receptor is controlled on the cell surface is essential in understanding how T-cell activity can be regulated in different microenvironments and in response to different pathogens.

Gut commensalism, cytokines, and central nervous system demyelination

There is increasing support for the importance of risk factors such as genetic makeup, obesity, smoking, vitamin D insufficiency, and antibiotic exposure contributing to the development of autoimmune diseases, including human multiple sclerosis (MS). Perhaps the greatest environmental risk factor associated with the development of immune-mediated conditions is the gut microbiome. Microbial and helminthic agents are active participants in shaping the immune systems of their hosts. This concept is continually reinforced by studies in the burgeoning area of commensal-mediated immunomodulation. The clinical importance of these findings for MS is suggested by both their participation in disease and, perhaps of greater clinical importance, attenuation of disease severity. Observations made in murine models of central nervous system demyelinating disease and a limited number of small studies in human MS suggest that immune homeostasis within the gut microbiome may be of paramount importance in maintaining a disease-free state. This review describes three immunological factors associated with the gut microbiome that are central to cytokine network activities in MS pathogenesis: T helper cell polarization, T regulatory cell function, and B cell activity. Comparisons are drawn between the regulatory mechanisms attributed to first-line therapies and those described in commensal-mediated amelioration of central nervous system demyelination.

Genetic association of rs1520333 G/A polymorphism in the IL7 gene with multiple sclerosis susceptibility in Isfahan population

Background:

Multiple sclerosis (MS) is an inflammatory neurodegenerative disease in which the insulating membrane of central nervous system is damaged. The etiology of MS includes both genetic and environmental causes. A Genome — Wide Association Study (GWAS) recognized genetic single nucleotide polymorphisms (SNP) linked with MS predisposition among which immunologically related genes are considerably over signified. The purpose of the present study is to explore the association of rs1520333 C/T polymorphism in the IL7 gene variants with the risk of MS in a subset of Iranian population.

Materials and Methods:

In this case — control study, 110 cases with MS and 110 controls were contributed. DNA was extracted from blood samples and to amplify the fragment of interest contain rs1520333 SNP, polymerase chain reaction — restriction fragment length polymorphism method was implemented for genotyping of the DNA samples with a specific restriction enzyme (MwoI).

SPSS for Windows software (version 18.0; SPSS, Chicago, IL, USA) was used for statistical analysis.

Result:

We demonstrated the important association between G allele [odds ratio (OR) =1.6614, confidence interval (CI) =1.12-2.47, P = 0.0124] and GG genotype (OR = 7.45, 95% CI = 2.13-25.97, P 0.0016) of the rs1520333 SNP for susceptibility to MS after adjustment for age, and gender. OR adjusted for age, gender, and body mass index has displayed similar outcomes.

Conclusion:

These results indicate that the rs1520333 SNP is a significant susceptibility gene variant for development of MS in the Iranian population. Nevertheless, functional studies are required to completely elucidate how this SNP contributed to MS pathogenesis.

Interleukin-12 (IL-12), but not IL-23, induces the expression of IL-7 in microglia and macrophages: implications for multiple sclerosis

Interleukin-12 (IL-12) p70 and IL-23 are bioactive cytokines and their biological functions are becoming clear. Increased expression of IL-7 in the central nervous system as well as in peripheral immune cells is associated with multiple sclerosis and experimental allergic encephalomyelitis. Here, we describe the induction of IL-7 in primary mouse and human microglia, BV-2 microglial cells, mouse peritoneal macrophages and astrocytes by IL-12p70. Interestingly, IL-12 strongly induced the expression of IL-7 whereas IL-23 and other p40 family members remained weak inducers of IL-7 in these cell types. Consistently, IL-12, but not IL-23 and other p40 family members, induced IL-7 promoter-driven luciferase activity in microglial cells. Among various stimuli tested, IL-12 emerged as the most potent stimulus followed by bacterial lipopolysaccharide and HIV-1 gp120 in inducing the activation of IL-7 promoter in microglial cells. Furthermore, increase in IL-7 mRNA expression by over-expression of IL-12p35 subunit, but not p40 and IL-23 p19 subunit, confirm that p35, but not p40 and p19, is responsible for the induction of IL-7. Finally, by using primary microglia from IL-12 receptor β1-deficient (IL-12Rβ1(-/-)) and IL-12Rβ2(-/-) mice, we demonstrate that IL-12 induces the expression of IL-7 in microglia and macrophages via both IL-12Rβ2 and IL-12Rβ1. These studies delineate a novel biological function of IL-12 that is absent in IL-23 and other p40 family members.

Interleukin-7 is decreased and maybe plays a pro-inflammatory function in primary immune thrombocytopenia

Primary immune thrombocytopenia (ITP) is an autoimmune disease with many immune dysfunctions, including over-proliferation and apoptosis resistance of auto-reactive lymphocytes. This study aimed to determine the effects of interleukin (IL)-7 on the cytokine production and survival of peripheral blood mononuclear cells and bone marrow mononuclear cells from ITP patients. We found that the plasma IL-7 levels in peripheral blood from ITP patients were lower than that of the normal controls, and it had positive correlation with platelet counts. However, the levels of IL-7 did not change in bone marrow serum of ITP patients compared with that of normal controls. The result of further stimulation experiments in vitro showed that IL-7 up-regulated the apoptosis of autologous platelets, promoted the proliferation and secretion of interferon-γ, tumor necrosis factor-α as well as IL-10 of lymphocyte both from peripheral blood and bone marrow. As the role of IL-7 in apoptosis-resistance and stimulation of pro-inflammatory cytokines, we speculated that decreased IL-7 in peripheral blood, maybe, is a consequence of the negative feedback of the pro-inflammatory function in ITP patients.

Activation of islet autoreactive naïve T cells in infants is influenced by homeostatic mechanisms and antigen-presenting capacity

Islet autoimmunity precedes type 1 diabetes onset. We previously found that islet autoimmunity rarely starts before 6 months of age but reaches its highest incidence already at ∼1 year of age. We now examine whether homeostatic expansion and immune competence changes seen in a maturating immune system may account for this marked variation in islet autoimmunity risk in the first year of life. We found naïve proinsulin- and GAD65-responsive T cells in cord blood (CB) of healthy newborns, with highest responses observed in children with type 1 diabetes-susceptible HLA-DRB1/DQB1 genotypes. Homeostatic expansion characteristics with increased IL-7 concentrations and enhanced T-cell responsiveness to IL-7 were observed throughout the first year of life. However, the ability of antigen-presenting cells to activate naïve T cells was compromised at birth, and CB monocytes had low surface expression of CD40 and HLA class II. In contrast, antigen presentation and expression of these molecules had reached competent adult levels by the high incidence age of 8 months. We propose that temporal changes in islet autoimmunity seroconversion in infants are a consequence of the changing balance between homeostatic drive and antigen presentation competence. These findings are relevant for early prevention of type 1 diabetes.

The human IL-7 receptor gene: deletions, polymorphisms and mutations

Most T cell subsets depend on IL-7 for survival. IL-7 binds to IL-7Rα and γc, initiating the signaling cascade. Deletion of IL-7Ra in humans has, for some time, been known to cause severe combined immunodeficiency. More recently, polymorphisms in IL-7R have been shown be a risk factor for a number of diseases that are autoimmune or involve excess immune and inflammatory responses including multiple sclerosis, type 1 diabetes, rheumatoid arthritis, primary biliary cirrhosis, inflammatory bowel disease, atopic dermatitis, inhalation allergy, sarcoidosis and graft-versus host disease. The polymorphism that affects risk to most of these immunopathologies is T244I at the border of the extracellular domain and the transmembrane region. The same region has recently been shown to harbor gain-of-function mutations in acute lymphoblastic leukemia. These studies have suggested new therapies that target the IL-7 pathway.

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.

IL-7 and lymphopenia

Interleukin-7 (IL-7) is a growth and anti-apoptotic factor for T-lymphocytes, with potential for clinical use in the treatment of immunodeficiencies due to loss of T-cells. Lymphopenia induced by disease (HIV infection, hemodialysis or Idiopathic CD4+ lymphopenia) or by treatment (high dose chemotherapy or depleting antibodies) for cancer or auto-immune diseases results in increased circulating levels of IL-7 which decline with T-cell recovery, however, the mechanism of such response remains to be elucidated. Furthermore, IL-7 is a major player in the regulation of peripheral T-cell homeostasis and as such is an important candidate cytokine for therapy aimed at improving T-cell reconstitution following lymphopenia. Anti- IL-7 is on the other hand proposed to treat conditions where IL-7 may play a more direct role in pathogenesis such as autoimmune disease like Rheumatoid Arthritis, Multiple Sclerosis or Inflammatory Bowel disease.

Modulating T-cell homeostasis with IL-7: preclinical and clinical studies

Interleukin-7 (IL-7) is required for the development and survival of T cells and plays a critical role in modulating T-cell homeostasis. This review will address current understanding of IL-7 biology, review recent clinical experiences and discuss potential future clinical applications of IL-7, or IL-7 blockade, in the setting of disease.

Live from the liver: hepatocyte IL-7

Interleukin 7 (IL-7), which is required for T cell survival, was previously found in lymphoid tissues. In this issue of Immunity, Sawa et al. (2009) have identified the liver as a new source of IL-7.

Variation in the IL7RA and IL2RA genes in German multiple sclerosis patients

Variation in the genes encoding the interleukin (IL) 7 and IL2 receptor alpha chains (IL7RA, IL2RA) was recently found associated with multiple sclerosis (MS). We evaluated the role of these two genes in a large German MS case-control cohort. Five single nucleotide polymorphisms (SNPs) in IL7RA and four in IL2RA were genotyped in 1319 MS patients and 908 controls by means of restriction enzyme digestion or TaqMan assays and subsequently evaluated for association with MS. IL7RA expression was measured via quantitative real time PCR in 24 subjects. We replicated the association of exon 6 variation (rs6897932) in IL7RA with MS. Yet, this association was only found in patients with primary progressive (pp) or secondary progressive (sp) disease course (p=0.0004). Expression analysis did not show differences in IL7RA expression depending on genotypes at this locus, while reduced expression of the soluble receptor was observed in patients with pp and sp MS irrespective of genotype. In the IL2RA gene, significant associations of SNPs in introns 3 and 7 with MS subtypes were obvious. Together these results confirm involvement of polymorphisms in the IL7RA and IL2RA genes in MS pathogenesis and suggest that IL7RA variation may primarily affect chronic disease courses.

Genetic association analysis of the interleukin 7 gene (IL7) in multiple sclerosis

IL7 is a nonredundant cytokine, essential for T cell survival and development in humans. We genotyped nine tagging single nucleotide polymorphisms (SNP), representing all parts of the IL7 gene, in 1,210 Swedish multiple sclerosis (MS) patients and 1,234 healthy controls. None of the SNPs showed a significantly different distribution in MS, and haplotype analysis also failed to reveal differences between patients and controls. We conclude that the IL7 gene is very unlikely to influence the genetic susceptibility to MS in this population.

Ectopic lymphoid-organ development occurs through interleukin 7-mediated enhanced survival of lymphoid-tissue-inducer cells

Development of Peyer's patches and lymph nodes requires the interaction between CD4+ CD3- IL-7Ralpha+ lymphoid-tissue inducer (LTi) and VCAM-1+ organizer cells. Here we showed that by promoting their survival, enhanced expression of interleukin-7 (IL-7) in transgenic mice resulted in accumulation of LTi cells. With increased IL-7 availability, de novo formation of VCAM-1+ Peyer's patch anlagen occurred along the entire fetal gut resulting in a 5-fold increase in Peyer's patch numbers. IL-7 overexpression also led to formation of multiple organized ectopic lymph nodes and cecal patches. After immunization, ectopic lymph nodes developed normal T cell-dependent B cell responses and germinal centers. Mice overexpressing IL-7 but lacking either RORgamma, a factor required for LTi cell generation, or lymphotoxin alpha1beta2 had neither Peyer's patches nor ectopic lymph nodes. Therefore, by controlling LTi cell numbers, IL-7 can regulate the formation of both normal and ectopic lymphoid organs.

Interleukin 7 receptor alpha chain (IL7R) shows allelic and functional association with multiple sclerosis

Multiple sclerosis is a demyelinating neurodegenerative disease with a strong genetic component. Previous genetic risk studies have failed to identify consistently linked regions or genes outside of the major histocompatibility complex on chromosome 6p. We describe allelic association of a polymorphism in the gene encoding the interleukin 7 receptor alpha chain (IL7R) as a significant risk factor for multiple sclerosis in four independent family-based or case-control data sets (overall P = 2.9 x 10(-7)). Further, the likely causal SNP, rs6897932, located within the alternatively spliced exon 6 of IL7R, has a functional effect on gene expression. The SNP influences the amount of soluble and membrane-bound isoforms of the protein by putatively disrupting an exonic splicing silencer.

IL-7 in allogeneic transplant: clinical promise and potential pitfalls

Much progress has been made in the field of allogeneic stem cell transplantation. However, one major barrier is the delay in immune recovery that can persist for months post-transplant and results in increased susceptibility to infection and relapse of malignancy. Strategies to improve immune recovery must be balanced with the potential for those therapies to exacerbate graft vs host disease. Interleukin 7 is a member of the gammac cytokine family that is required for T-cell development and maintenance of naïve T-cell populations. In addition, IL-7 plays a major role in the expansion of mature T-cells that occurs during lymphopenia and therapeutic IL-7 can enhance both quantitative and functional immune recovery following T-cell depletion. Thus, this agent holds much promise as an immunorestorative agent and as an adjuvant to vaccines or adoptive immunotherapy. Clinic trials with IL-7 are underway. Murine studies with IL-7 in the allogeneic transplant have demonstrated that the potent immune effects of this agent can also be achieved in this setting. However, these studies have indicated that the potential for IL-7 to worsen GVHD exists and that this effect may abrogate the immune benefits. Thus, careful consideration of how best to incorporate IL-7 into allogeneic trials will be needed if the full potential of this agent is to be realized.

Reduced suppressive effect of CD4+CD25high regulatory T cells on the T cell immune response against myelin oligodendrocyte glycoprotein in patients with multiple sclerosis

Immunoregulatory T cells of (CD4+)CD25+ phenotype suppress T cell function and protect rodents from organ-specific autoimmune disease. The human counterpart of this subset of T cells expresses high levels of CD25 and its role in human autoimmune disorders is currently under intense investigation. In multiple sclerosis (MS), a chronic inflammatory disease of the central nervous system (CNS), the activation of circulating self-reactive T cells with specificity for myelin components is considered to be an important disease initiating event. Here, we investigated whether MS is associated with an altered ability of (CD4+)CD25high regulatory T cells (Treg) to confer suppression of myelin-specific immune responses. Whereas Treg frequencies were equally distributed in blood and cerebrospinal fluid of MS patients and did not differ compared to healthy controls, the suppressive potency of patient-derived (CD4+)CD25high T lymphocytes was impaired. Their inhibitory effect on antigen-specific T cell proliferation induced by human recombinant myelin oligodendrocyte protein as well as on immune responses elicited by polyclonal and allogeneic stimuli was significantly reduced compared to healthy individuals. The effect was persistent and not due to responder cell resistance or altered survival of Treg, suggesting that a defective immunoregulation of peripheral T cells mediated by (CD4+)CD25high T lymphocytes promotes CNS autoimmunity in MS.

Cross-sectional and longitudinal analysis of myelin-reactive T cells in patients with multiple sclerosis

Activated myelin-specific T cells are thought to mediate inflammatory tissue damage in multiple sclerosis (MS). Applying a large panel of myelin antigens, we demonstrate the direct ex vivo detection of viable IFN-gamma/TNF-alpha producing CD4+/CD69+ T cells 6 hours after antigenic challenge, by intracellular flow cytometry in 3/33 MS patients and 2/26 healthy controls with calculated frequencies of (mean +/- SEM): 0.031% +/- 0.002% versus 0.037% +/- 0.029%. By comparison, the recently developed IL-7 modified proliferation assay revealed i) a higher number of individuals showing myelin reactivity (17/37 MS patients and 12/24 healthy individuals) and ii) a significant difference in the response to myelin basic protein (MBP) between the two groups in a longitudinal analysis, indicating a higher activity of myelin-specific T cells in MS patients. Our data provide new perspectives in detecting pathogenetically relevant T cells, but clearly demonstrate the different conclusions which must be drawn from various approaches concerning the quantification of autoreactive T cells.

Interleukin-7 deficiency in rheumatoid arthritis: consequences for therapy-induced lymphopenia

We previously demonstrated prolonged, profound CD4⁺ T-lymphopenia in rheumatoid arthritis (RA) patients following lymphocyte-depleting therapy. Poor reconstitution could result either from reduced de novo T-cell production through the thymus or from poor peripheral expansion of residual T-cells. Interleukin-7 (IL-7) is known to stimulate the thymus to produce new T-cells and to allow circulating mature T-cells to expand, thereby playing a critical role in T-cell homeostasis. In the present study we demonstrated reduced levels of circulating IL-7 in a cross-section of RA patients. IL-7 production by bone marrow stromal cell cultures was also compromised in RA. To investigate whether such an IL-7 deficiency could account for the prolonged lymphopenia observed in RA following therapeutic lymphodepletion, we compared RA patients and patients with solid cancers treated with high-dose chemotherapy and autologous progenitor cell rescue. Chemotherapy rendered all patients similarly lymphopenic, but this was sustained in RA patients at 12 months, as compared with the reconstitution that occurred in cancer patients by 3–4 months. Both cohorts produced naïve T-cells containing T-cell receptor excision circles. The main distinguishing feature between the groups was a failure to expand peripheral T-cells in RA, particularly memory cells during the first 3 months after treatment. Most importantly, there was no increase in serum IL-7 levels in RA, as compared with a fourfold rise in non-RA control individuals at the time of lymphopenia. Our data therefore suggest that RA patients are relatively IL-7 deficient and that this deficiency is likely to be an important contributing factor to poor early T-cell reconstitution in RA following therapeutic lymphodepletion. Furthermore, in RA patients with stable, well controlled disease, IL-7 levels were positively correlated with the T-cell receptor excision circle content of CD4⁺ T-cells, demonstrating a direct effect of IL-7 on thymic activity in this cohort.

Immune reconstitution

Lymphocyte recovery is delayed following autologous haematopoietic stem cell transplantation (HSCT). B-cells recover before T-cells and CD8+ before CD4+ T-cells. The initial phase of T-cell recovery is dependent upon the expansion of mature host T-cells that have survived conditioning or are transferred back with the graft. This phase is therefore quicker when the graft is not CD34+ selected. Subsequently, naïve T-cells appear. Naïve CD4+ T-cell recovery is thymus dependent and starts at around 6-9 months. Naïve CD8+ recovery occurs earlier and seems less thymus dependent. Immune function recovers later than lymphocyte number, the former being dependent on a broad repertoire and diversity of effector function. We currently do not know which reconstitution markers are more likely to predict prolonged disease remission as opposed to relapse. Similarly, it is unclear whether disease-specific factors influence reconstitution. A continued, close collaboration between scientists and physicians should both improve the outcomes of HSCT and also provide important pathogenic information about the diseases under treatment.

Identification of 11 novel and common single nucleotide polymorphisms in the interleukin-7 receptor-alpha gene and their associations with multiple sclerosis

We have investigated the interleukin-7 receptor (IL-7R) alpha-chain gene as a positional and functional candidate gene for susceptibility to multiple sclerosis (MS), in view of its chromosomal location on 5p14-p12, a region that has shown suggestive linkage in MS genome screens, and its role in T- and B-cell proliferation and reactivity. Amplification and DNA sequencing of the IL-7Ralpha gene in pooled and individual samples identified 13 single nucleotide polymorphisms (SNPs), 11 of which are novel, including three in the promoter region, three in exons encoding amino-acid changes (ACC(Thr)66ATC(Ile), ATC(Ile)244ACC(Thr), ATC(Ile)336GTC(Val)), four in introns and one in the 3' untranslated region. Four IL-7R haplotypes were identified for nine SNPs, showing linkage disequilibrium across the gene, and allowing haplotype frequency determination from just three of the nine SNPs. Genotyping of the -504 polymorphism in 101 MS and 90 controls showed a suggestive (P=0.1) association of the T allele with MS; however, this was not supported by transmission disequilibrium testing in 186 MS trio families (P=0.8). There were trends towards an increase of the GTG+ haplotype (odds ratio=1.45), and under-representation of the TTA+ haplotype (OR=0.65) in DRB1*1501-positive MS cases, suggesting that larger sample sizes and comparison in more defined MS patient groups may support an association with the IL-7R gene. These polymorphisms would also be useful for studying genetic associations with other immunologic diseases.