IPEX is a unique X-linked syndrome characterized by immune dysfunction, polyendocrinopathy, enteropathy, and a variety of autoimmune phenomena

B cells are critical for autoimmune pathology in Scurfy mice

Impaired regulatory T-cell function results in a severe chronic autoimmune disease affecting multiple organs in Scurfy mice and humans with the immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) syndrome. Previous studies have shown that T helper cells but not cytotoxic T cells are critical for the disease pathology. Whether this T-cell subset is responsible directly for tissue inflammation or rather indirectly via the interaction with B cells or myeloid cells is largely unknown. To study this and to identify potential therapeutic targets for this lethal disease we investigated the contribution of B cells to this complex autoimmune phenotype. We show that B cells and the production of autoantibodies plays a major role for skin, liver, lung, and kidney inflammation and therapeutic depletion of B cells resulted in reduced tissue pathology and in prolonged survival. In contrast, the absence of B cells did not impact systemic T-cell activation and hyperreactivity, indicating that autoantibody production by B cells may be a major factor for the autoimmune pathology in mice deficient for regulatory T cells.

The role of FOXP3 in the development and metastatic spread of breast cancer

The transcription factor FOXP3 is widely known for its role in the development and function of immunoregulatory T cells. However, it has been discovered recently that FOXP3 is also expressed in epithelial cells of the normal human breast, ovary and prostate. Aggressive cancer of these epithelial tissues often correlates with abnormal expression of FOXP3, which can be either absent or underexpressed at transcript or protein levels. It is becoming clear that this failure of normal FOXP3 expression can result in dysregulation of the expression of a range of oncogenes which have been implicated in the development and metastasis of cancer. Recent evidence suggests that FOXP3 might also regulate chemokine receptor expression, providing a possible explanation for the chemokine-driven, tissue-specific spread that is characteristic of many cancers. This review first summarises the general structure, function and properties of FOXP3. This is followed by an analysis of the tumour-suppressive properties of this transcription factor, with particular reference to the development and chemokine-mediated spread of human breast cancer. A final section focuses on potential applications of this new knowledge for therapeutic intervention.

Dominant gain-of-function STAT1 mutations in FOXP3 wild-type immune dysregulation-polyendocrinopathy-enteropathy-X-linked-like syndrome

BACKGROUND

Mutations in signal transducer and activator of transcription (STAT) 1 cause a broad spectrum of disease, ranging from severe viral and bacterial infections (amorphic alleles) to mild disseminated mycobacterial disease (hypomorphic alleles) to chronic mucocutaneous candidiasis (CMC; hypermorphic alleles). The hypermorphic mutations are also associated with arterial aneurysms, autoimmunity, and squamous cell cancers.

OBJECTIVE

We sought to investigate the role of STAT1 gain-of-function mutations in phenotypes other than CMC.

METHODS

We initially screened patients with CMC and autoimmunity for STAT1 mutations. We functionally characterized mutations in vitro and studied immune profiles and regulatory T (Treg) cells. After our initial case identifications, we explored 2 large cohorts of patients with wild-type forkhead box protein 3 and an immune dysregulation-polyendocrinopathy-enteropathy-X-linked (IPEX)-like phenotype for STAT1 mutations.

RESULTS

We identified 5 children with polyendocrinopathy, enteropathy, and dermatitis reminiscent of IPEX syndrome; all but 1 had a variety of mucosal and disseminated fungal infections. All patients lacked forkhead box protein 3 mutations but had uniallelic STAT1 mutations (c.629 G>T, p.R210I; c.1073 T>G, p.L358W, c.796G>A; p.V266I; c.1154C>T, T385M [2 patients]). STAT1 phosphorylation in response to IFN-γ, IL-6, and IL-21 was increased and prolonged. CD4(+) IL-17-producing T-cell numbers were diminished. All patients had normal Treg cell percentages in the CD4(+) T-cell compartment, and their function was intact in the 2 patients tested. Patients with cells available for study had normal levels of IL-2-induced STAT5 phosphorylation.

CONCLUSIONS

Gain-of-function mutations in STAT1 can cause an IPEX-like phenotype with normal frequency and function of Treg cells.

Targeting the "cytokine storm" for therapeutic benefit

Inflammation is the body's first line of defense against infection or injury, responding to challenges by activating innate and adaptive responses. Microbes have evolved a diverse range of strategies to avoid triggering inflammatory responses. However, some pathogens, such as the influenza virus and the Gram-negative bacterium Francisella tularensis, do trigger life-threatening "cytokine storms" in the host which can result in significant pathology and ultimately death. For these diseases, it has been proposed that downregulating inflammatory immune responses may improve outcome. We review some of the current candidates for treatment of cytokine storms which may prove useful in the clinic in the future and compare them to more traditional therapeutic candidates that target the pathogen rather than the host response.

3p14.1 de novo microdeletion involving the FOXP1 gene in an adult patient with autism, severe speech delay and deficit of motor coordination

Interstitial deletion of chromosome region 3p14.1, including FOXP1 gene, is relatively rare and, until recently, there were no strong evidences to support the hypothesis that this microdeletion could play a role in the etiology of genomic disorders. Here, we report on an adult patient with a recognizable phenotype of autism, severe speech delay, deficit of motor coordination and typical dysmorphic features. Analysis of a dense whole genome single-nucleotide polymorphism (SNP) array showed a 1Mb interstitial deletion of chromosome region 3p14.1 including the entire coding region of FOXP1 (MIM 605515) gene. In order to study the parental origin of the deletion, we analyzed selected SNPs in the deleted area in the proband and his parents showing Mendelian incompatibilities suggesting a de novo deletion on the chromosome of paternal origin. Despite the frequency of this genomic alteration has not been estimated, our patient confirm the hypothesis that microdeletion of 3p14.1 seems to be a rare cause of cognitive disorders and that haploinsufficiency of FOXP1 may play a role in neurological and language deficits in patients carrying a 3p14.1 deletion. Finally, our patient is also important because useful to further delineate the clinical spectrum secondary to the 3p14.1 microdeletions.

Genetic basis of altered central tolerance and autoimmune diseases: a lesson from AIRE mutations

The thymus is a specialized organ that provides an inductive environment for the development of T cells from multipotent hematopoietic progenitors. Self-nonself discrimination plays a key role in inducing a productive immunity and in preventing autoimmune reactions. Tolerance represents a state of immunologic nonresponsiveness in the presence of a particular antigen. The immune system becomes tolerant to self-antigens through the two main processes, central and peripheral tolerance. Central tolerance takes place within the thymus and represents the mechanism by which T cells binding with high avidity self-antigens, which are potentially autoreactive, are eliminated through so-called negative selection. This process is mostly mediated by medullary thymic epithelia cells (mTECs) and medullary dendritic cells (DCs). A remarkable event in the process is the expression of tissue-specific antigens (TSA) by mTECs driven by the transcription factor autoimmune regulator (AIRE). Mutations in this gene result in autoimmune polyendocrinopathy candidiasis ectodermal dystrophy (APECED), a rare autosomal recessive disease (OMIM 240300). Thus far, this syndrome is the paradigm of a genetically determined failure of central tolerance and autoimmunty. Patients with APECED have a variable pattern of autoimmune reactions, involving different endocrine and nonendocrine organs. However, although APECED is a monogenic disorder, it is characterized by a wide variability of the clinical expression, thus implying a further role for disease-modifying genes and environmental factors in the pathogenesis. Studies on this polyreactive autoimmune syndrome contributed enormously to unraveling several issues of the molecular basis of autoimmunity. This review focuses on the developmental, functional, and molecular events governing central tolerance and on the clinical implication of its failure.

Genetic association of FOXP3 gene polymorphisms with allograft rejection in renal transplant patients

AIM

FOXP3 gene is known to be important for regulatory T cell development and function, and is associated with the rejection of human kidney transplants. The present study was therefore conducted to determine the effect of FOXP3 polymorphisms on allograft rejection in renal transplant recipients.

METHODS

A total of 166 adult patients were categorized into either a Rejection group (65 patients) or a No rejection group (101 patients). Rs3761547, rs3761548 and rs2232365 variant alleles in the FOXP3 gene were genotyped using a TaqMan probe technique, and their relationships with rejection were investigated.

RESULTS

There was no significant difference in the genotype frequencies of rs3761547 and rs2232365 variants between patients with and without rejection history (P > 0.05). Binary logistic regression analysis showed that the rs3761548 AA genotype carriers were associated with about a fourfold greater risk for rejection compared with CC genotype (5 years post-transplant: odds ratio 3.95, 95% confidence interval 1.27-12.29, P = 0.018). Kaplan-Meier analysis revealed a lower mean time to the first rejection in rs3761548 AA compared with CC genotype patients (Log rank = 4.303, P = 0.038). Multivariate Cox regression analysis indicated that rs3761548 AA genotype carriers have up to about a twofold (hazard ratio 2.37, 95% confidence interval 1.17-4.80, P = 0.017) higher risk for rejection than CC carriers.

CONCLUSION

Our study suggests an association between FOXP3 rs3761548 polymorphisms and allograft rejection in renal transplantation. This association should be further proven in large prospective studies because of the small sample size and confounding factors in this retrospective study.

The distinct and overlapping phenotypic spectra of FOXP1 and FOXP2 in cognitive disorders

Rare disruptions of FOXP2 have been strongly implicated in deficits in language development. Research over the past decade has suggested a role in the formation of underlying neural circuits required for speech. Until recently no evidence existed to suggest that the closely related FOXP1 gene played a role in neurodevelopmental processes. However, in the last few years, novel rare disruptions in FOXP1 have been reported in multiple cases of cognitive dysfunction, including intellectual disability and autism spectrum disorder, together with language impairment. As FOXP1 and FOXP2 form heterodimers for transcriptional regulation, one may assume that they co-operate in common neurodevelopmental pathways through the co-regulation of common targets. Here we compare the phenotypic consequences of FOXP1 and FOXP2 impairment, drawing on well-known studies from the past as well as recent exciting findings and consider what these tell us regarding the functions of these two genes in neural development.

Pulmonary complications of endocrine and metabolic disorders

There are many important respiratory manifestations of endocrine and metabolic diseases in children. Acute and chronic pulmonary infections are the most common respiratory abnormalities in patients with diabetes mellitus, although cardiogenic and non-cardiogenic pulmonary oedema are also possible. Pseudohypoaldosteronism type 1 may be indistinguishable from cystic fibrosis (CF) unless serum aldosterone, plasma renin activity, and urinary electrolytes are measured and mutation analysis rules out CF. Hypo- and hyperthyroidism may alter lung function and affect the central respiratory drive. The thyroid hormone plays an essential role in lung development, surfactant synthesis, and lung defence. Complications of hypoparathyroidism are largely due to hypocalcaemia. Laryngospasm can lead to stridor and airway obstruction. Ovarian tumours, benign or malignant, may present with unilateral or bilateral pleural effusions. Metabolic storage disorders, primarily as a consequence of lysosomal dysfunction from enzymatic deficiencies, constitute a diverse group of rare conditions that can have profound effects on the respiratory system.

Proteomics plus genomics approaches in primary immunodeficiency: the case of immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) syndrome

Immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) is a rare syndrome due to a mutation in the forkhead box protein 3 gene (FOXP3) leading to an impaired regulatory T cell (T(reg) ) activity associated both with skewed T helper type 2 (Th2) response and autoreactive phenomena. The purpose of this study was to describe a combined proteomics and genomics approach to comprehensively evaluate clinical and immunological phenotypes of patients affected by IPEX. T cell receptor (TCR)-Vβ repertoire and peripheral blood lymphocytes phenotype from three brothers affected by IPEX were studied by flow cytometry. Specific immunoglobulin (Ig)E were evaluated by means of an allergenic molecules microarray [immuno solid-phase allergen chip (ISAC)]. Total RNA was extracted and hybridized to Affymetrix oligonucleotide arrays to obtain quantitative gene-expression levels. No FOXP3 protein was detectable within CD127(-) CD25(high) CD4(+) T cells from peripheral blood. A T cell-naive phenotype (CD62L(+) CD45R0(-)) associated with a reduction of both CD26 and CD7 expression and a TCR-Vβ 8 and 22 family expansions were found. B lymphocytes were mainly CD5(+) (B1) cells expressing a naive phenotype (tcl1(+) CD27(-)). The three IPEX patients had severe food allergy and specific IgE reactivity to cow's milk allergens, a hen's egg allergen and a wheat allergen. Gene expression profile analysis revealed a dysregulation associated mainly with Th1/Th2 pathways. The multiplexing evaluation reported in this study represents a comprehensive approach in the assessment of genetic conditions affecting the immune system such as the IPEX syndrome, paving the way for the development of diagnostic tools to improve the standard clinical and immunological profiling of the disease.

Inflammatory bowel disease: is it a primary immunodeficiency?

Inflammatory bowel diseases (IBD) such as ulcerative colitis and Crohn's disease are chronic and relapsing conditions, characterized by abdominal pain, diarrhea, bleeding and malabsorption. IBD has been considered a hyperinflammatory state due to disturbed interactions between the immune system and the commensal bacterial flora of the gut. However, there is evidence that Crohn's disease might be the consequence of a reduced release of pro-inflammatory cytokines and an impaired acute inflammatory response, thereby suggesting that IBD might be an immunodeficiency rather than an excessive inflammatory reaction. This theory has been supported by observations in patients with primary immunodeficiencies such as the Wiskott-Aldrich syndrome and IPEX (immunodysregulation, polyendocrinopathy, enteropathy, X-linked syndrome). In contrary, defects in the anti-inflammatory down-regulation of the immune response as they are seen in patients with Mendelian defects in the IL10 signaling pathway support the hyper-inflammatory theory. In this review, we describe and discuss primary immunodeficiencies associated with IBD and show that the bowel is a highly sensitive indicator of dysregulations, making IBD a model disease to study and identify key regulators required to balance the human mucosal immune system.

CD147 (Basigin/Emmprin) identifies FoxP3+CD45RO+CTLA4+-activated human regulatory T cells

Human CD4+FoxP3+ T cells are functionally and phenotypically heterogeneous providing plasticity to immune activation and regulation. To better understand the functional dynamics within this subset, we first used a combined strategy of subcellular fractionation and proteomics to describe differences at the protein level between highly purified human CD4+CD25+ and CD4+CD25− T-cell populations. This identified a set of membrane proteins highly expressed on the cell surface of human regulatory T cells (Tregs), including CD71, CD95, CD147, and CD148. CD147 (Basigin or Emmprin) divided CD4+CD25+ cells into distinct subsets. Furthermore, CD147, CD25, FoxP3, and in particular CTLA-4 expression correlated. Phenotypical and functional analyses suggested that CD147 marks the switch between resting (CD45RA+) and activated (CD45RO+) subsets within the FoxP3+ T-cell population. Sorting of regulatory T cells into CD147− and CD147+ populations demonstrated that CD147 identifies an activated and highly suppressive CD45RO+ Treg subset. When analyzing CD4+ T cells for their cytokine producing potential, CD147 levels grouped the FoxP3+ subset into 3 categories with different ability to produce IL-2, TNF-α, IFN-γ, and IL-17. Together, this suggests that CD147 is a direct marker for activated Tregs within the CD4+FoxP3+ subset and may provide means to manipulate cells important for immune homeostasis.

Clinical and molecular characteristics of immunodysregulation, polyendocrinopathy, enteropathy, X-linked syndrome in China

Immunodysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) syndrome is a rare X-linked recessive disorder causing life-threatening systemic autoimmunity because of immunodysregulation. The FOXP3 gene had been reported as the responsible gene, which was critical for the functions of CD4(+) CD25(+) FOXP3(+) regulatory T cells (Tregs) and maintenance of peripheral immunologic tolerance. So far, no IPEX patients with definite mutations in the FOXP3 gene had been reported in China. In this study, the genotypes and phenotypes were investigated in three IPEX infants from three unrelated Chinese families. Patient 1 (P1) presented with a classical clinical phenotype, whose mutation was a novel frameshift insertion in exon 11, led to the complete abrogation of Tregs. Patient 2 (P2) showed incomplete IPEX phenotype. He carried a missense mutation in exon 11 with slightly increased frequency of Tregs, whereas Patient 3 (P3) presented with a relatively mild classical phenotype and had a previously reported missense mutation in exon 10 with decreased frequency of Tregs. We firstly report three Chinese IPEX patients with definite mutations of FOXP3 gene. Our study indicated the potential correlation between the genotype and the phenotype of IPEX, which was different from the previous reports.

Obesity and susceptibility to autoimmune diseases

For decades, obesity has been considered to be the result of the complex interaction between genes and the environment and its pathogenesis is still unresolved. The discovery of hormones and neural mediators responsible for the control of food intake and metabolism at the hypothalamic level has provided fundamental insights into the complicated pathways that control food intake. However, the molecular basis for the association between obesity and low-degree chronic inflammation is still unknown. More recently, the discovery of leptin, one of the most abundant adipocyte-derived hormones, has suggested that nutritional status, through leptin secretion, can control immune self-tolerance modulating Treg suppressive function and responsiveness. Furthermore, recent experimental evidence has shown the presence of an abundant adipose tissue-resident Treg population responsible for the control of metabolic parameters and glucose homeostasis. Better knowledge of the intricate network of interactions among leptin-related energy regulation, Treg activities and obesity could lead to valuable strategies for therapeutic intervention in obesity and obesity-associated insulin resistance.

SOCS1 is essential for regulatory T cell functions by preventing loss of Foxp3 expression as well as IFN-{gamma} and IL-17A production

SOCS1 is required to restrict IFN-γ and IL-17 expression and maintain Foxp3 expression in and function of regulatory T cells.

Regulatory T cells (T_reg cells) maintain immune homeostasis by limiting inflammatory responses. SOCS1 (suppressor of cytokine signaling 1), a negative regulator of cytokine signaling, is necessary for the suppressor functions of T_reg cells in vivo, yet detailed mechanisms remain to be clarified. We found that Socs1^−/− T_reg cells produced high levels of IFN-γ and rapidly lost Foxp3 when transferred into Rag2^−/− mice or cultured in vitro, even though the CNS2 (conserved noncoding DNA sequence 2) in the Foxp3 enhancer region was fully demethylated. Socs1^−/− T_reg cells showed hyperactivation of STAT1 and STAT3. Because Foxp3 expression was stable and STAT1 activation was at normal levels in Ifnγ^−/−Socs1^−/− T_reg cells, the restriction of IFN-γ–STAT1 signaling by SOCS1 is suggested to be necessary for stable Foxp3 expression. However, Ifnγ^−/−Socs1^−/− T_reg cells had hyperactivated STAT3 and higher IL-17A (IL-17) production compared with Ifnγ^−/−Socs1^+/+ T_reg cells and could not suppress colitis induced by naive T cells in Rag2^−/− mice. In vitro experiments suggested that cytokines produced by Socs1^−/− T_reg cells and Ifnγ^−/−Socs1^−/− T_reg cells modulated antigen-presenting cells for preferential Th1 and Th17 induction, respectively. We propose that SOCS1 plays important roles in T_reg cell integrity and function by maintaining Foxp3 expression and by suppressing IFN-γ and IL-17 production driven by STAT1 and STAT3, respectively.

Expression of CD4+ forkhead box P3 (FOXP3)+ regulatory T cells in inflammatory bowel disease

OBJECTIVE

Forkhead box P3 (FOXP3) plays an important role in the development and function of CD4(+) regulatory T (Treg) cells. In this study the percentage of CD4(+) FOXP3(+) Treg cells in peripheral blood mononuclear cells (PBMC) and the frequency of Treg cells in the colonic mucosa of patients with inflammatory bowel disease (IBD) were investigated.

METHODS

The percentage of CD4(+) FOXP3(+) Treg cells in PBMC was analyzed by flow cytometry. Immunohistochemistry was used to examine the FOXP3(+) cells in the inflamed mucosa. Real-time polymerase chain reaction and Western blot were used to detect the expressions of FOXP3 mRNA and protein in PBMC and mucosal biopsy specimens of IBD patients, respectively.

RESULTS

Together with the decrease of percentage of Treg cells in PBMC, we found that the frequency of Treg cells increased significantly in inflamed mucosa of active or inactive Crohn's disease (CD) and ulcerative colitis (UC). The expressions of FOXP3 mRNA and protein increased in inflamed mucosa when compared with those in healthy controls, especially the FOXP3 mRNA in patients with active CD or UC. Interestingly, the expression of FOXP3 protein in active UC was higher than that in active CD.

CONCLUSIONS

There was a decrease of CD4(+) FOXP3(+) Treg cells in peripheral blood and an accumulation of Treg cells in inflamed mucosa. These data suggested that the suppressive function of Treg cells may be partially inhibited and this could be an important factor in the recurrence of disease, especially in UC.

Identification of FOXP3-negative regulatory T-like (CD4(+)CD25(+)CD127(low)) cells in patients with immune dysregulation, polyendocrinopathy, enteropathy, X-linked syndrome

Immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) syndrome is an autoimmune disorder caused by mutations in the FOXP3 gene, which plays a key role in the generation of CD4(+)CD25(+)regulatory T (Treg) cells. We selected CD127 as the surface marker of Treg cells to illustrate the development and function of Treg cells in IPEX syndrome. CD4(+)CD25(+)FOXP3(+) T cells, the putative Treg cells, were almost completely absent in all patients. Importantly, a substantial number of CD4(+)CD25(+)CD127(low) T cells were observed in 3 IPEX patients with hypomorphic mutations in the FOXP3 gene. We demonstrated that CD4(+)CD25(+)CD127(low) T cells isolated from these 3 patients exhibited an appreciable suppressive activity on effector T cell proliferation, although less than that displayed by Treg cells from healthy controls. These results suggest that genetically altered FOXP3 can drive the generation of functionally immature Treg cells, but that intact FOXP3 is necessary for the complete function of Treg cells.

Solution structure and backbone dynamics of the DNA-binding domain of FOXP1: insight into its domain swapping and DNA binding

FOXP1 belongs to the P-subfamily of forkhead transcription factors and contains a conserved forkhead DNA-binding domain. According to size exclusion chromatography analysis, the forkhead domain of FOXP1 existed as a mixture of monomer and dimer. The dissociation constants of the forkhead domain of wild-type, C61S, and C61Y mutants of FOXP1 were 27.3, 28.8, and 332.0 μM, respectively. In contrast, FOXP1 A39P mutant formed only a monomer. NMR analysis also showed that FOXP1 C61S and C61Y mutants existed as a mixture. The solution structure of FOXP1 A39P/C61Y mutant was similar to the X-ray structure of the FOXP2 monomer. Comparison of backbone dynamics of FOXP1 A39P/C61Y and C61Y mutants showed that the residues preceding helix 3, the hinge region, exhibited the largest conformational exchange in FOXP1 monomer. The A39 residue of FOXP1 dimer has a lower order parameter with internal motion on the ps-ns timescale, suggesting that the dynamics of the hinge region of FOXP1 are important in the formation of the swapped dimer. The analysis also showed that the residues exhibiting the motions on the ps-ns and μs-ms timescales were located at the DNA-binding surface of FOXP1, suggesting the interactions between FOXP1 and DNA may be highly dynamic.

Functional type 1 regulatory T cells develop regardless of FOXP3 mutations in patients with IPEX syndrome

Mutations of forkhead box p3 (FOXP3), the master gene for naturally occurring regulatory T cells (nTregs), are responsible for the impaired function of nTregs, resulting in an autoimmune disease known as the immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) syndrome. The relevance of other peripheral tolerance mechanisms, such as the presence and function of type 1 regulatory T (Tr1) cells, the major adaptive IL-10-producing Treg subset, in patients with IPEX syndrome remains to be clarified. FOXP3^mutated Tr1-polarized cells, differentiated in vitro from CD4⁺ T cells of four IPEX patients, were enriched in IL-10⁺IL-4⁻IFN-γ⁺ T cells, a cytokine production profile specific for Tr1 cells, and expressed low levels of FOXP3 and high levels of Granzyme-B. IPEX Tr1 cells were hypoproliferative and suppressive, thus indicating that FOXP3 mutations did not impair their function. Furthermore, we isolated Tr1 cell clones from the peripheral blood of one FOXP3^null patient, demonstrating that Tr1 cells are present in vivo and they can be expanded in vitro in the absence of WT FOXP3. Overall, our results (i) show that functional Tr1 cells differentiate independently of FOXP3, (ii) confirm that human Tr1 and nTregs are distinct T-cell lineages, and (iii) suggest that under favorable conditions Tr1 cells could exert regulatory functions in IPEX patients.

Murine autoimmune hearing loss mediated by CD4+ T cells specific for β-tubulin

Autoimmune inner ear disease is described as progressive, bilateral although asymmetric, sensorineural hearing loss and can be improved by immunosuppressive therapy. We showed that the inner ear autoantigen β-tubulin is capable of inducing experimental autoimmune hearing loss (EAHL) in mice. Immunization of BALB/c mice with β-tubulin resulted in hair cell loss and hearing loss, effects that were not seen in animals immunized with control peptide. Moreover, the EAHL model showed that β-tubulin responsiveness involved CD4(+) T cells producing IFN-γ, and T cell mediation of EAHL was determined by significantly increased auditory brainstem response after adoptive transfer of β-tubulin-activated CD4(+) T cells into naive BALB/c recipients. The potential mechanisms responsible for the observed pathology of EAHL can be attributed to decreased frequency and impaired suppressive function of regulatory T cells. Our study suggests that EAHL may be a T cell-mediated organ-specific autoimmune disorder of the inner ear.

The power and the promise of restimulation-induced cell death in human immune diseases

Controlled expansion and contraction of lymphocytes both during and after an adaptive immune response are imperative to sustain a healthy immune system. Both extrinsic and intrinsic pathways of lymphocyte apoptosis are programmed to eliminate cells at the proper time to ensure immune homeostasis. Genetic disorders of apoptosis described in mice and humans have established Fas and Bim as critical pro-apoptotic molecules responsible for T-cell death in response to T-cell receptor restimulation and cytokine withdrawal, respectively. Emerging evidence prompts revision of this classic paradigm, especially for our understanding of restimulation-induced cell death (RICD) and its physiological purpose. Recent work indicates that RICD employs both Fas and Bim for T-cell deletion, dispelling the notion that these molecules are assigned to mutually exclusive apoptotic pathways. Furthermore, new mouse model data combined with our discovery of defective RICD in X-linked lymphoproliferative disease (XLP) patient T cells suggest that RICD is essential for precluding excess T-cell accumulation and associated immunopathology during the course of certain infections. Here, we review how these advances offer a refreshing new perspective on the phenomenon of T-cell apoptosis induced through antigen restimulation, including its relevance to immune homeostasis and potential for therapeutic interventions.

Effector and regulatory T-cell subsets in autoimmunity and tissue inflammation

Many autoimmune diseases are driven by self-reactive T helper cells. Until recently, organ-specific autoimmune diseases were primarily associated with Th1 cells but not Th2 cells. However, the discovery of a number of new effector T-cell subsets, like Th17 and Th9 cells, and regulatory T cells, like Tregs and Tr1 cells, has changed the way we view and understand autoimmunity at cellular and molecular levels. In recent years, IL-17-producing Th17 cells have emerged as major players in autoimmunity. The complicated relationship between Th1 and Th17 cells, as well as the intricate balance between Tregs and Th17 cells, provides a basis for understanding the immunological mechanisms that induce and regulate autoimmunity. Here, we give an overview of the interplay between different effector T-cell subsets and regulatory T-cell subsets, and how they contribute to the development of autoimmunity and tissue inflammation.

Regulatory T cells in obesity: the leptin connection

Studies to understand the pathogenesis of obesity have revealed mediators that are responsible for the control of food intake and metabolism at the hypothalamic level. However, molecular insight explaining the link between obesity and low-degree chronic inflammation remains elusive. The adipocyte-derived hormone leptin, and thereby the nutritional status, could control immune self-tolerance by affecting regulatory T (Treg) cell responsiveness and function. Furthermore, resident Treg cells, which are capable of modulating metabolism and glucose homeostasis, are abundant in adipose tissue. Here, we provide an update on recent findings relating Treg cells to obesity and discuss how the intricate network of interactions among leptin, Treg cells and adipose tissue might provide new strategies for therapeutic interventions.

Gastrointestinal and hepatic manifestations of primary immune deficiency diseases

Primary immune deficiency diseases (PIDs) are a heterogeneous group of inherited diseases characterized by variable genetic immune defects, conferring susceptibility to recurrent infections. They have a vast array of manifestations some of which involve the gastrointestinal and hepatobiliary systems. These complications can be the consequence of five different factors, namely, infection, autoimmune process, unregulated inflammation, malignancies and complications of therapeutic intervention. They may precede the PID diagnosis and, once developed, they pose high risk of morbidity. Untrained clinicians may treat these manifestations only at the level of their presentation, leaving the PIDs dangerously undiagnosed. In fact, early diagnosis of PIDs and accompanied gastrointestinal and hepatic complications clearly require appropriate treatment, and in-turn lead to an improved quality of life for the patient. To improve the awareness of gastroenterologists and related health care providers about these diseases, we have reviewed herein the complications of different PIDs focusing on gastrointestinal and hepatic manifestation.

Bone marrow transplantation for primary immunodeficiency diseases

Advances in immunology have led to a breathtaking expansion of recognized primary immunodeficiency diseases (PID) with over 120 disease-related genes identified. In North America alone more than 1000 children have received allogeneic blood or marrow transplant over the past 30 years, with the majority surviving long term. This review presents results and highlights challenges and notable advances, including novel less toxic conditioning regimens, to transplant the more common and severe forms of PID. HLA-matched sibling donors remain the ideal option, however, advances in living donor unrelated HSCT and banked umbilical cord blood grafts provide hope for all children with severe PID.

Polymorphisms in the FOXP3 gene in Han Chinese psoriasis patients

BACKGROUND

Psoriasis is a common dermatological disorder, in which autoimmunity plays an important role. CD4(+)CD25(+) regulatory T cells (T-regs) have been suggested to be involved in the pathogenesis of some autoimmune diseases. T-regs express the fork head/winged helix transcription factor, FOXP3, which appears to be of key importance in the development and function of T-regs. Studies have found that single-nucleotide polymorphisms (SNPs) in the FOXP3 gene contribute to susceptibility to some autoimmune disorders. However, information about FOXP3 gene in psoriasis is limited.

OBJECTIVE

This study evaluated the association between FOXP3 gene SNPs and susceptibility to psoriasis in a Han Chinese population.

METHODS

In a hospital-based case-control study, 524 patients with psoriasis and 549 psoriasis-free controls were recruited according to age and gender. We investigated four SNPs in the FOXP3 gene (-6054, deletion/ATT; -3279, A/C; -924, A/G; IVS9+459, A/G) in psoriatic patients, and assessed allele and genotype frequencies in psoriatic patients (237 females, 287 males) and normal controls (272 females, 277 males). The polymorphisms were genotyped using the PCR sequence-specific primer (PCR-SSP) technique and PCR-restriction fragment length polymorphism (RFLP) analysis.

RESULTS

We found that increased risk of psoriasis was associated with the FOXP3 -3279 AC genotype (adjusted OR, 1.32; 95% CI, 1.01-1.74) and the combined AC+AA genotype (adjusted OR, 1.38; 95% CI, 1.07-1.78), compared with the -3279 CC genotype. We also found that an increased risk of psoriasis was associated with the FOXP3 IVS9+459 GG genotype (adjusted OR, 2.24; 95% CI, 1.41-3.58). However, the combined GA+GG genotype showed no such tendency (adjusted OR=1.28; 95% CI, 1.00-1.64), compared with the IVS9+459 AA genotype. There was no evidence of an increased risk associated with the FOXP3-6054 deletion/ATT or FOXP3-924 A/G genotype. In combined genotype analyses, the FOXP3-3279 AC+AA genotype was more obviously associated in males (adjusted OR=1.60, 95% CI=1.11-2.31) and severe psoriasis patients (PASI score >20; adjusted OR=1.97, 95% CI=1.41-2.75). Meanwhile, the FOXP3 IVS9+459 GA+GG genotype was also associated with severe psoriasis patients (adjusted OR=1.69, 95% CI=1.21-2.36).

CONCLUSIONS

FOXP3 polymorphisms appear to contribute to the risk of psoriasis in a Han Chinese population. Larger studies are needed to confirm these findings.

Foxp3 regulates megakaryopoiesis and platelet function

OBJECTIVE

Platelets are crucial for hemostasis and are vital regulators of inflammation. Foxp3 is a key transcription factor for T regulatory cell development. Humans with IPEX (immune dysregulation, polyendocrinopathy, enteropathy, x-linked) and the scurfy (Foxp3(sf)) mouse have mutations in the Foxp3 gene that lead to a host of pathologies including autoimmunity and skin diseases. Scurfy mice and some humans with IPEX are also thrombocytopenic. The purpose of this study was to determine whether the absence of functional Foxp3 leads to defects in megakaryocytes and platelets.

METHODS AND RESULTS

We discovered that human and mouse megakaryocytes express Foxp3 mRNA and protein. Using shRNA and Foxp3(sf) mice, we demonstrated that Foxp3-deficient mouse and human megakaryocyte progenitors exhibited proliferation defects. Striking platelet abnormalities were observed in both an IPEX patient and Foxp3(sf) mice. Impaired platelet spreading and release of TGF-beta and CD40 ligand (CD40L), and abnormal levels of plasma CD40L were observed in a case of IPEX syndrome. Foxp3(sf) mice were thrombocytopenic and had increased platelet volume and altered serum levels of CD40L, TXB(2), and TGF-beta.

CONCLUSIONS

These findings provide compelling new evidence that Foxp3 is needed for proper megakaryopoiesis and plays a role in regulating platelet function including spreading and release.

Instability of the transcription factor Foxp3 leads to the generation of pathogenic memory T cells in vivo

Regulatory T (T_reg) cells play a central role in maintaining immune homeostasis. However, little is known about the stability of T_reg cells in vivo. In this study, we demonstrate that a significant percentage of cells exhibited transient or unstable Foxp3 expression. These exFoxp3⁺ T cells express an activated-memory T cell phenotype, and produced inflammatory cytokines. Moreover, exFoxp3 cell numbers increased in inflamed tissues under autoimmune conditions. Adoptive transfer of autoreactive exFoxp3 cells led to the rapid-onset of diabetes. Finally, T cell receptor repertoire analyses suggested that exFoxp3 cells develop from both natural and adaptive T_reg cells. Thus, the generation of potentially autoreactive effector T cells as a consequence of Foxp3 instability has important implications for understanding autoimmune disease pathogenesis.

Instability of the transcription factor Foxp3 leads to the generation of pathogenic memory T cells in vivo

Regulatory T cells (T(reg) cells) are central to the maintenance of immune homeostasis. However, little is known about the stability of T(reg) cells in vivo. In this study, we demonstrate that a substantial percentage of cells had transient or unstable expression of the transcription factor Foxp3. These 'exFoxp3' T cells had an activated-memory T cell phenotype and produced inflammatory cytokines. Moreover, exFoxp3 cell numbers were higher in inflamed tissues in autoimmune conditions. Adoptive transfer of autoreactive exFoxp3 cells led to the rapid onset of diabetes. Finally, analysis of the T cell receptor repertoire suggested that exFoxp3 cells developed from both natural and adaptive T(reg) cells. Thus, the generation of potentially autoreactive effector T cells as a consequence of Foxp3 instability has important implications for understanding autoimmune disease pathogenesis.

Hematopoietic stem cell transplantation for pediatric autoimmune disease: where we stand and where we need to go

In children, autoimmune diseases and their therapies cause significant morbidity, especially in those with severe or refractory disease. The constant development of new immunosuppressants and targeted biological therapies leads to a unique 'moving target' with regard to the gold standard of treatment for these patients. However, incidental findings of cure after hematopoietic stem cell transplant (HSCT) in patients with concomitant benign or malignant hematologic disorders and autoimmune disease raise the question of whether HSCT can be used as upfront therapy for patients with severe autoimmune diseases. Animal data have been helpful in investigating both the efficacy of this modality and the mechanisms underlying cure. The potential for a therapeutic 'graft vs autoimmunity' (GVA) effect with an allogeneic approach highlights the already acknowledged need for clinical trials of allogeneic vs autologous transplant in these diseases where an autologous transplant would be the 'intuitive' albeit potentially erroneous choice. We critically review the data generated in the field thus far, and emphasize the need for an organized, interdisciplinary approach to conduct prospective clinical trials to answer these and other questions and advance the field.

From autoimmune enteropathy to the IPEX (immune dysfunction, polyendocrinopathy, enteropathy, X-linked) syndrome

The term autoimmune enteropathy (AIE) was applied to a form of "intractable diarrhoea" with serum gut autoantibodies, characterized by male predominance, early onset, poor response to parenteral nutrition and several autoimmune diseases, mainly type 1 diabetes. In recent years the vague concept of AIE has became more precise thanks to the discovery of its genetic and molecular basis. The FOXP3 molecule is crucial for the generation and maturation of regulatory T cells (Treg) expressing CD4+ and CD25+ molecules. Mutations of the FOXP3 gene, located in X chromosome, produce a syndrome with Immune dysfunction, Polyendocrinopathy, Enteropathy and X-linked inheritance (IPEX). The majority of the ancient so-called AIE cases probably correspond to the new IPEX syndrome, even in female patients who may have some autosomal genetic variants. Besides FOXP3, other molecules are likely to be involved in the generation and function of Treg and its deficiency may also enhance autoimmune disease and IPEX-like syndromes. Meanwhile, the important pathogenic role previously ascribed to gut autoantibodies has vanished, with it remaining as having only certain screening usefulness.

Naturally occurring and inducible T-regulatory cells modulating immune response in allergic asthma

RATIONALE

T-regulatory cells (Tregs) are potent immunomodulators in allergic asthma.

OBJECTIVES

We evaluated the functional effects of Tregs by adoptively transferring naturally occurring CD4(+)CD25(+) Tregs (NTregs) and CD4(+)CD25(-) inducible Tregs (iTregs) from lung and spleens of green fluorescent protein (GFP)-transgenic Balb/c mice into cockroach-sensitized and -challenged mice.

METHODS

GFP-labeled NTregs and iTregs were adoptively transferred into cockroach-sensitized and -challenged mice. Airway hyperresponsiveness (AHR) to methacholine was examined using a single-chamber, whole-body plethysmograph and invasive tracheostomy.

MEASUREMENTS AND MAIN RESULTS

Adoptive transfer of either NTregs or iTregs from lung or spleen reversed airway inflammation and AHR to methacholine, and the effect lasted for at least 4 weeks. GFP-labeled iTregs up-regulated CD25 and forkhead-winged transcriptional factor box protein 3 and migrated to lymph node and lung. Lung CD4(+)CD25(+) T cells isolated from each group of recipient mice were inducible costimulatory molecule-high and programmed death (PD)-1-positive; however, higher expression of PD-1 was found in the spleen iTregs (S25(-)) and lung iTregs (L25(-)) groups. Higher levels of transforming growth factor-beta and IL-10 mRNA transcripts and bronchoalveolar lavage fluid IL-10 and INF-gamma levels were observed in lung CD4(+)CD25(+) cells from the L25(-) and S25(-) cell-recipient mice than from lung NTregs (L25(+)) and spleen NTregs (S25(+)) cell-recipient mice. Adoptive transfer of either cell type significantly reduced bronchoalveolar lavage fluid IL-4, IL-5, and IL-13 levels.

CONCLUSIONS

Tregs reverse AHR and airway inflammation; however iTregs that differentiated into IL-10-producing CD4(+) type 1 cells in the lung exert their suppressive activity likely by higher levels of transforming growth factor-beta, IL-10, IFN-gamma, and elevated levels of PD-1 compared with NTregs. Hence, PD-1 may be a conduit for reversing AHR by Tregs and a plausible target for treating asthma.

CD25+ T(reg) specifically suppress auto-Ab generation against pancreatic tissue autoantigens

To study B-cell tolerance against non-lymphoid tissue autoantigens, we generated transgenic rat insulin promoter (RIP)-OVA/hen egg lysozyme (HEL) mice expressing the model antigens, OVA and HEL, in pancreatic islets. Their vaccination with OVA or HEL induced far less auto-Ab titers compared with non-transgenic controls. Depletion of CD25(+) cells during immunization completely restored auto-Ab production, but did not affect antibodies against a foreign control antigen. Depletion at later time-points was not effective. OVA-specific CD25(+) FoxP3(+) T(reg) were more frequent in the autoantigen-draining pancreatic LN than in other secondary lymphatics of RIP-OVA/HEL mice. Consistently, B cells were suppressed in that LN and also in the spleen, which is known to concentrate circulating antigen, such as the antigens used for vaccination. Suppression involved preventing expansion of autoreactive B cells in response to autoantigen, reducing antibody production per B-cell and isotype changes. These findings demonstrate that CD25(+) T(reg) suppress auto-Ab production against non-lymphoid tissue antigens in an antigen-specific manner.

FOXP3 and its role in the immune system

FOXP3 is a member of the forkhead transcription factor family. Unlike other members, it is mainly expressed in a subset of CD4+ T-cells that play a suppressive role in the immune system. A function of FOXP3 is to suppress the function of NFAT and NFkappaB and this leads to suppression ofexpression of many genes including IL-2 and effector T-cell cytokines. FOXP3 acts also as a transcription activator for many genes induding CD2S, Cytotoxic T-Lymphocyte Antigen 4 (CTLA4), glucocorticoid-induced TNF receptorfamily gene (GITR) andfolate receptor 4. FOXP3+ T-cells are made in the thymus and periphery. The FOXP3+ T-cells made in the thymus migrate to secondary lymphoid tissues and suppress antigen priming of lymphocytes. Antigen priming of naive FOXP3 T-cdlls and naive FOXP3 T-cells leads to generation of memory FOXP3+ T-cells which are efficient in migration to nonlymphoid tissues. Memory FOXP3+ T-cells are, therefore, effective in suppression of effector T-cell function, while naive FOXP3 T-cells are adept at suppressing the early immune responses in lymphoid tissues. Both naive and memory FOXP3 T-cells are required for effective maintenance of tolerance and prevention of autoimmune diseases throughout the body. Many factors such as cytokines and noncytokine factors regulate the generation of FOXP3 T-cells. For example, retinoic acid, produced by the dendritic cells and epithelial cells in the intestine, works together with TGF-beta1 and promotes generation of small intestine-homing FOXP3 T-cells by upregulating the expression ofFOXP3 and gut homing receptors. FOXP3+ T-cells can be produced in vitro from autologous naive T-cells and, therefore, have great therapeutic potentials in treating a number of inflammatory diseases and grafi rejection.

Digestive histopathological presentation of IPEX syndrome

Immunodysregulation, polyendocrinopathy, enteropathy, and X-linked inheritance (IPEX) syndrome is a well recognized and particularly severe form of autoimmune enteropathy. It has an X-linked recessive transmission, and is caused by mutations in the FOXP3 gene. We studied the intestinal morphological changes characterizing IPEX syndrome in a series of 12 children with a molecularly confirmed diagnosis. Histological examination of duodenal, gastric and colonic biopsies were retrospectively reviewed and compared by two independent experienced pathologists. In parallel, the presence of circulating anti-enterocyte antibodies was analysed using an indirect immunofluorescence technique and a quantitative radioligand assay against the 75-kDa autoantigen. The morphology of the inflammatory gut lesions could be categorized into three different entities, namely graft-vs-host disease-like changes (9/12 patients), a coeliac disease-like pattern (2/12) and an enteropathy with a complete depletion of goblet cells (1/12). Our results do not suggest any phenotype-genotype correlation. Circulating antibodies were detected in all 12 patients, with an anti-brush border pattern (11/12) and anti-goblet cell antibodies (1/12), as well as by a radioligand assay. The histological presentation of autoimmune enteropathy is rather variable. However, a graft-vs-host disease-like pattern associated with positive anti-enterocyte antibodies is the most frequent intestinal presentation of IPEX syndrome, and constitutes a very valuable tool for pathologists to suspect this diagnosis.

Clinical and molecular aspects of autoimmune enteropathy and immune dysregulation, polyendocrinopathy autoimmune enteropathy X-linked syndrome

PURPOSE OF REVIEW

Autoimmune enteropathy (AIE) is a distinct cause of severe and persistent inflammatory diarrhea in children. Recent research data allowed us to gain a first insight in the pathogenesis of AIE. On the basis of this data, we will discuss new aspects of AIE emphasizing new diagnostic and therapeutic possibilities.

RECENT FINDINGS

With the discovery of disease-causing mutations in the FOXP3 gene in patients with AIE, a dramatic advance in the understanding of AIE was made. Subsequent studies indicated that FOXP3 is a key transcription factor indispensable for regulatory functions of T cells pointing to a critical role of regulatory T-cell homeostasis in the development of AIE. Abnormal FOXP3 expression results in defective regulatory functions of T cells, which in turn cause a systemic T-cell-mediated autoaggressive disorder, now called immune dysregulation, polyendocrinopathy autoimmune enteropathy X-linked syndrome. Upon systematic review, we describe different phenotypes of immune dysregulation polyendocrinopathy autoimmune enteropathy X-linked syndrome, as well as immune dysregulation polyendocrinopathy autoimmune enteropathy X-linked-like forms of AIE, which are FOXP3 independent. No genotype-phenotype correlation could be established so far.

SUMMARY

On the basis of the profound immune dysregulation in AIE, new, most often T-cell-oriented treatment strategies were developed. The recent molecular advances in the understanding of AIE give a clear rational for the use of immunosuppression (combining steroids and tacrolimus or rapamycine) to stabilize AIE patients or to perform bone marrow transplantation in those who do not respond to immunomodulation.

Clinical and molecular profile of a new series of patients with immune dysregulation, polyendocrinopathy, enteropathy, X-linked syndrome: inconsistent correlation between forkhead box protein 3 expression and disease severity

BACKGROUND

Immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) syndrome is an autoimmune genetic disorder caused by mutation of the forkhead box protein 3 gene (FOXP3), a key regulator of immune tolerance.

OBJECTIVE

We sought to provide clinical and molecular indicators that facilitate the understanding and diagnosis of IPEX syndrome.

METHODS

In 14 unrelated affected male subjects who were given diagnoses of IPEX syndrome based on FOXP3 gene sequencing, we determined whether particular FOXP3 mutations affected FOXP3 protein expression and correlated the molecular and clinical data.

RESULTS

Molecular analysis of FOXP3 in the 14 subjects revealed 13 missense and splice-site mutations, including 7 novel mutations. Enteropathy, generally associated with endocrinopathy and eczema, was reported in all patients, particularly in those carrying mutations within FOXP3 functional domains or mutations that altered protein expression. However, similar genotypes did not always result in similar phenotypes in terms of disease presentation and severity. In addition, FOXP3 protein expression did not correlate with disease severity.

CONCLUSION

Severe autoimmune enteropathy, which is often associated with increased IgE levels and eosinophilia, is the most prominent early manifestation of IPEX syndrome. Nevertheless, the disease course is variable and somewhat unpredictable. Therefore genetic analysis of FOXP3 should always be performed to ensure an accurate diagnosis, and FOXP3 protein expression analysis should not be the only diagnostic tool for IPEX syndrome.

The effect of costimulatory and interleukin 2 receptor blockade on regulatory T cells in renal transplantation

Regulatory T cells (Treg) are critical regulators of immune tolerance. Both IL-2 and CD28-CD80/CD86 signaling are critical for CD4(+)CD25(+)FOXP3(+) Treg survival in mice. Yet, both belatacept (a second-generation CTLA-4Ig) and basiliximab (an anti-CD25 monoclonal antibody) are among the arsenal of current immunotherapies being used in kidney transplant patients. In this study, we explored the direct effect of basiliximab and belatacept on the Tregs in peripheral blood both in the short term and long term and in kidney biopsies of patients with acute rejection. We report that the combined belatacept/basiliximab therapy has no long-term effect on circulating Tregs when compared to a calcineurin inhibitor (CNI)-treated group. Moreover, belatacept-treated patients had a significantly greater number of FOXP3(+) T cells in graft biopsies during acute rejection as compared to CNI-treated patients. Finally, it appears that the basiliximab caused a transient loss of both FOXP3(+) and FOXP3(-) CD25(+) T cells in the circulation in both treatment groups raising important questions about the use of this therapy in tolerance promoting therapeutic protocols.

Alpha-CTLA-4 mAb-associated panenteritis: a histologic and immunohistochemical analysis

Monoclonal antibodies (mAbs) against the cytotoxic T lymphocyte antigen-4 (CTLA-4) molecule are used as an adjuvant to experimental tumor immunization protocols in the treatment of malignant melanomas and ovarian cancers. Aside from noted early therapeutic successes, a spectrum of adverse effects, including severe gastroenteritis, has been reported. We report herein our observations of 5 patients who developed severe gastrointestinal toxicity affecting the gastric, small intestinal, and colonic mucosa. The endoscopic findings were variable, ranging from normal to diffusely erythematous and ulcerated mucosa. The constant histologic findings included a lymphoplasmacytic expansion of the lamina propria with increase in intraepithelial lymphocytes. Increased epithelial apoptosis was also a distinctive feature. Cryptitis and glandular inflammation were observed in the colon, ileum, and stomach, whereas villous blunting was present in the ileal and duodenal mucosa. Immunohistochemical analysis revealed a marked increase of all T-cell subsets (CD3+, CD4+, and CD8+) and of CD4CD25 regulatory T cells. We conclude that the panenteritis associated with injection of alpha-CTLA-4 mAbs demonstrates histology resembling autoimmune enteropathy. Furthermore, although the pathogenesis of immune dysregulation after the infusion of alpha-CTLA-4 mAbs remains unclear, we suspect that the increased number of regulatory T cells in the gastrointestinal mucosa may play a role in the pathogenicity.

Suppression of HIV-specific and allogeneic T cell activation by human regulatory T cells is dependent on the strength of signals

Regulatory T cells (Tregs) suppress immune responses against both self and non-self antigens. Tregs require activation through the T cell receptor (TCR) and IL-2 to exert their suppressive functions. However, how strength of TCR signals modulate the potency of Treg-mediated suppression of antigen-specific T cell activation remain unclear. We found that both strength of TCR signals and ratios of Tregs to target cells, either through superantigen, allogeneic antigens or HIV-specific peptides, modified the suppressive ability of Tregs. While human Tregs were able to mediate suppression in the presence of only autologous antigen-presenting cells, this was much less efficient as compared to when Tregs were activated by allogeneic dendritic cells. In another physiologically relevant system, we show that the strength of peptide stimulation, high frequency of responder CD8+ T cells or presence of high IL-2 can override the suppression of HIV-specific CD8+ T cells by Tregs. These findings suggest that ratios and TCR activation of human Tregs, are important parameters to overcome robust immune responses to pathogens or allogeneic antigens. Modulating the strength of T cell signals and selective enhancement or depletion of antigen-specific Tregs thus may have implications for designing potent vaccines and regulating immune responses during allogeneic transplantation and chronic infections.

Primary immune deficiency disorders presenting as autoimmune diseases: IPEX and APECED

BACKGROUND

Several primary immune deficiency disorders are associated with autoimmunity and malignancy, suggesting a state of immune dysregulation. The concept of immune dysregulation as a direct cause of autoimmunity in primary immune deficiency disorders (PIDDs) has been strengthened by the recent discovery of distinct clinical entities linked to single-gene defects resulting in multiple autoimmune phenomena including immune dysregulation, polyendocrinopathy, enteropathy and X-linked (IPEX) syndrome, and autoimmune polyendocrinopathy, candidiasis and ectodermal dystrophy (APECED) syndrome.

CONCLUSION

Reviewing recent advances in our understanding of the small subgroup of PIDD patients with defined causes for autoimmunity may lead to the development of more effective treatment strategies for idiopathic human autoimmune diseases.

Neonatal diabetes mellitus

An explosion of work over the last decade has produced insight into the multiple hereditary causes of a nonimmunological form of diabetes diagnosed most frequently within the first 6 months of life. These studies are providing increased understanding of genes involved in the entire chain of steps that control glucose homeostasis. Neonatal diabetes is now understood to arise from mutations in genes that play critical roles in the development of the pancreas, of beta-cell apoptosis and insulin processing, as well as the regulation of insulin release. For the basic researcher, this work is providing novel tools to explore fundamental molecular and cellular processes. For the clinician, these studies underscore the need to identify the genetic cause underlying each case. It is increasingly clear that the prognosis, therapeutic approach, and genetic counseling a physician provides must be tailored to a specific gene in order to provide the best medical care.

PIP3 pathway in regulatory T cells and autoimmunity

Regulatory T cells (Tregs) play an important role in preventing both autoimmune and inflammatory diseases. Many recent studies have focused on defining the signal transduction pathways essential for the development and the function of Tregs. Increasing evidence suggest that T-cell receptor (TCR), interleukin-2 (IL-2) receptor (IL-2R), and co-stimulatory receptor signaling are important in the early development, peripheral homeostasis, and function of Tregs. The phosphoinositide-3 kinase (PI3K)-regulated pathway (PIP3 pathway) is one of the major signaling pathways activated upon TCR, IL-2R, and CD28 stimulation, leading to T-cell activation, proliferation, and cell survival. Activation of the PIP3 pathway is also negatively regulated by two phosphatidylinositol phosphatases SHIP and PTEN. Several mouse models deficient for the molecules involved in PIP3 pathway suggest that impairment of PIP3 signaling leads to dysregulation of immune responses and, in some cases, autoimmunity. This review will summarize the current understanding of the importance of the PIP3 pathway in T-cell signaling and the possible roles this pathway performs in the development and the function of Tregs.