Altered signaling through IL-12 receptor in children with very high serum IgE levels

An alteration of Th1/Th2 homeostasis may lead to diseases in humans. In this study, we investigated whether an impaired IL-12R signaling occurred in children with elevated serum IgE levels divided on the basis of the IgE levels (group A: >2000 kU/l; group B: <2000 kU/l). We evaluated the integrity of the IL-12R signaling through the analysis of phosphorylation/activation of STAT4, and mRNA expression and membrane assembly of the receptor chains. At a functional level, a proliferative defect of lymphocytes from group A patients was observed. In these patients, an abnormal IL-12R signaling was documented, and this finding was associated with abnormal expression of the IL-12Rb2 chain. Our data indicate that in patients with very high IgE levels the generation of Th1 response is impaired, and that this abnormality associates with abnormal IL-12R signaling

From Murine to Human Nude/SCID: The Thymus, T-Cell Development and the Missing Link

Primary immunodeficiencies (PIDs) are disorders of the immune system, which lead to increased susceptibility to infections. T-cell defects, which may affect T-cell development/function, are approximately 11% of reported PIDs. The pathogenic mechanisms are related to molecular alterations not only of genes selectively expressed in hematopoietic cells but also of the stromal component of the thymus that represents the primary lymphoid organ for T-cell differentiation. With this regard, the prototype of athymic disorders due to abnormal stroma is the Nude/SCID syndrome, first described in mice in 1966. In man, the DiGeorge Syndrome (DGS) has long been considered the human prototype of a severe T-cell differentiation defect. More recently, the human equivalent of the murine Nude/SCID has been described, contributing to unravel important issues of the T-cell ontogeny in humans. Both mice and human diseases are due to alterations of the FOXN1, a developmentally regulated transcription factor selectively expressed in skin and thymic epithelia

New insights and unsolved issues in congenital immunodeficiencies

Primary immunodeficiencies comprise more than 200 different disorders that affect the development and the functions of the immune system. Many scientific papers have been published on the molecular and cellular basis of the immune response and on the mechanisms involved in the correct development of immune system components. Although today we know the genetic and molecular basis of those principal mechanisms involved in the immune response, some aspect in this field remain unclear. In this thesis, during the three years of my PhD program, I have contributed to elucidate “New insights and unsolved issues in congenital immunodeficiencies”, through the combination of clinical, cellular, functional and molecular approaches. In particular, my research work is focused on the study role of c in cell cycle progression, strongly related to its cellular amount and GH-R signaling, defining the basis of the physiological interaction between endocrine and immune systems. I demonstrate, moreover, that this subunit is able to influence the cell cycle progression in a concentration dependent manner in lymploblastoid and neoplastic cell lines. Moreover, I participated to better define the functional role of FOXN1 transcription factor in the development of the T-cell ontogeny in the Nude/SCID syndrome. I also documented that FOXN1 is a possible cofactor in the development and differentiation of some structures in the central nervous system. Of note, this immunodeficiency is due to mutated gene expressed in non hematopoietic cells. In addition, I participated to the study of patients affected with A-T. In this context I contributed to evaluate the beneficial effect of betamethasone on therapy in these patients. Our data indicate that betamethasone is effective in A-T at a minimal dosage and that GILZ may be a useful biomarker of the clinical response. Finally, I also participate to give a contribution to the description of new mechanism in immunodeficiencies associated with unidentified molecular defects. Our data revealed that in a group of patients with high levels of serum IgE the IL-12R signaling was altered. Moreover, we documented the possibility of an autoreactive anti-lymphocyte antibody able to induce a SCID phenocopy. Overall, all my studies were designed in order to clarify unsolved issues and unknown mechanisms underlying the functionality of the immune system. These results could be useful both in the clinical practice and in the basic research of immunedeficiencies

The cellular amount of the common γ-chain influences spontaneous or induced cell proliferation

Mutations of the IL2RG encoding the common γ-chain (γc) lead to the X-linked SCID disease. Gene correction through ex vivo retroviral transduction restored the immunological impairment in the most of treated patients, although lymphoproliferative events occurred in five of them. Even though in two cases it was clearly documented an insertional mutagenesis in LMO2, it is conceivable that γc could have a role per se in malignant lymphoproliferation. The γc is a shared cytokine receptor subunit, involved also in growth hormone (GH) receptor signaling. Through short interfering RNA or using X-linked SCID B lympho-blastoid cell lines lacking γc, we demonstrate that self-sufficient growth was strongly dependent on γc expression. Furthermore, a correlation between γc amount and the extent of constitutive activation of JAK3 was found. The reduction of γc protein expression also reduced GH-induced proliferation and STAT5 nuclear translocation in B lymphoblastoid cell lines. Hence, our data demonstrate that γc plays a remarkable role in either spontaneous or GH-induced cell cycle progression depending on the amount of protein expression, suggesting a potential role as enhancing cofactor in lymphoproliferation. Copyright © 2009 by The American Association of Immunologists, Inc

La Sindrome Nude/SCID: dal modello murino al fenotipo umano

A proper normal immune response is initially based on the innate immunity, characterized by a rapid and nonspecific response to infections, and later on the adaptive immunity, characterized by a specific response to a particular pathogen. Disruption of any part of the orchestrated immune response can result in an inability to control infections and subsequent illness. Primary immunodeficiencies are congenital disorders of the immunological response, which can be divided into subgroups on the basis of the component of the immune system predominantly affected, including T, B, NK lymphocytes, phagocytic cells and complement proteins. The severe combined immunodeficiency (SCID), characterized by abnormalities of T, B and NK cells, consists of a group of distinct diseases associated with a severe clinical phenotype due to an impairment of both effector arms of the specific immunity. In the 1996, a novel form of SCID (MIM 601705; Pignata guarino syndrome) was described, and proposed as the human equivalent of the well known murine phenotype described by Flanagan in 1966. This murine model was defined as Nude/SCID. The hallmarks of the Nude/SCID phenotype are congenital alopecia, from which the term “Nude” for the spontaneous murine model, nail dystrophy and an intrinsic defect of the thymus, always associated with a profound T-cell defect. The affected mice described by Flanagan, also showed an inborn dysgenesis of the thymus resulting in a compromised immune system lacking T cells. Moreover, molecular studies on the nude murine model led to identify Foxn1 as the gene responsible of the Nude phenotype. Also in humans as in mice, the molecular analysis reveals alterations in FOXN1 gene. Of note, the immunological phenotype of these patients is characterized by a marked reduction of CD3+, CD4+ and CD8+ cells and by the absence of naïve CD4+CD45RA+ cells. It should be mentioned that studies performed in Nude/SCID mice gave a great contribution to the knowledge of cell-mediated immunity. In humans for a long time, the DiGeorge syndrome (DGS) was erroneously considered the human counterpart of the murine Nude/SCID phenotype. However, because of the profound differences among DGS and mouse Nude/SCID, the mouse model has been considered misleading to understand T-cell ontogeny in humans. The description of the human equivalent of the Nude/SCID syndrome unravelled many of the dilemmas of T-cell ontogeny in man. Novel knowledge in this field would be very helpful in the comprehension of the intimate mechanisms underlying the T-cell differentiation process in humans and in discovering novel clinical entities related to abnormalities of the process

Gamma chain transducing element: a shared pathway between endocrine and immune system

Several molecules, involved in the intracellular communication network, have been identified as the cause of primary immunodeficiencies. In most cases, these molecules are exclusively expressed in hematopoietic cells, being involved in cell development and/or functionality of terminal differentiated cells of immune system. In the case of gamma c, the abundance of the protein suggests a potential pleiotropic effect of the molecule. Immune and endocrine systems participate to an integrated network of soluble mediators that communicate and coordinate responsive cells to achieve effector functions in an appropriate fashion. It has been demonstrated a novel dependence of GH signaling on the common cytokines receptor gamma c in certain cell types, supporting the hypothesis of an interplay between endocrine and immune system. The evidence that different receptors share a few molecules may certainly lead to a better knowledge on the mechanism of coordination and integration of several pathways implicated in the control of cell growth and proliferation under physiological or pathogenic conditions. This review focuses on the gamma c as a common transducing element shared between several cytokines and growth hormone receptors, indicating a further functional link between endocrine and immune system

Efficacy of very-low-dose betamethasone on neurological symptoms in ataxia-telangiectasia

Ataxia-telangiectasia (A-T) is a non-curable neurodegenerative disorder, associated with progressive neurological dysfunction, oculocutaneous telangiectasia, immunodeficiency, predisposition to cancer and radiosensitivity. A recent study documented improvement in neurological symptoms after a short-term therapy with betamethasone in patients with A-T. Aim of this study was to evaluate the minimum therapeutically effective dosage of betamethasone on neurological symptoms of A-T. Methods: Six responsive patients with A-T, received two 20-day cycles of oral betamethasone at 0.01 and 0.03 mg/kg/day (10% and 30% of the previously used full dosage), each followed by a 20-day washout period. Clinical and laboratory evaluations were carried out at T0 and at the end of each cycle. Neurological assessment was performed through the Scale for the Assessment and Rating of Ataxia (SARA). The glucocorticoid-induced leucine zipper (GILZ) and glucocorticoid receptor (GR) RNA expression were evaluated before and during the trial through real-time PCR. Results: SARA scores significantly improved in all patients at the dosage of 0.03 mg/kg/day. In particular, three patients exhibited an improvement in 5/8 variables and two patients of 7 and 8 variables, respectively. Furthermore, the clinical improvement was already evident after the lower dosage. The basal GILZ and GR RNA expression were significantly lower in patients than in controls. GILZ expression increased in all patients after the beginning of the therapy, whereas no correlation between GR and the response was found. Conclusion: Our data indicate that betamethasone is effective in A-T at a minimal dosage and that GILZ may be a useful biomarker of the clinical response. This study provides Class IIIA evidence that betamethasone at very low dosage is effective in improving neurological signs of patients affected with ataxia-telangiectasia

FOXN1 mutation abrogates prenatal T-cell development in humans

Background The transcription factor FOXN1 is implicated in the differentiation of thymic and skin epithelial cells, and alterations in it are responsible for the Nude/SCID phenotype. During a genetic counselling programme offered to couples at risk in a community where a high frequency of mutated FOXN1 had been documented, the identification of a human FOXN1(-/-) fetus gave the unique opportunity to study T cell development in utero. Results Total blockage of CD4(+) T cell maturation and severe impairment of CD8(+) cells were documented. Evaluation of the variable-domain beta-chain (V beta) families' usage among T lymphocytes revealed that the generation of T cell receptor (TCR) diversity occurred to some extent in the FOXN1(-/-) fetus, although it was impaired compared with the control. A few non-functional CD8(+) cells, mostly bearing TCR gamma delta in the absence of CD3, were found. Discussion FOXN1 is crucial for in utero T cell development in humans. The identification of a limited number of CD8(+) cells suggests an extrathymic origin for these cells, implying FOXN1-independent lymphopoiesis