Francesco Perna

Glycogen storage disease type 1b (GSD-1b) is an autosomal-recessive disease caused by mutation of glucose-6–phosphate transporter and characterized by altered glycogen/glucose homeostasis. A higher frequency of autoimmune diseases has been observed in GSD-1b patients, but the molecular determinants leading to this phenomenon remain unknown. To address this question, we investigated the effect of glucose-6–phosphate transporter mutation on immune cell homeostasis and CD4⁺ T cell functions. In GSD-1b subjects, we found lymphopenia and a reduced capacity of T cells to engage glycolysis upon TCR stimulation. These phenomena associated with reduced expression of the FOXP3 transcription factor, lower suppressive function in peripheral CD4⁺CD25⁺FOXP3⁺ regulatory T cells, and an impaired capacity of CD4⁺CD25⁻ conventional T cells to induce expression of FOXP3 after suboptimal TCR stimulation. These data unveil the metabolic determinant leading to an increased autoimmunity risk in GSD-1b patients.

Screening of latent infection by Mycobacterium tuberculosis (LTBI) and treatment of positive subjects is the key point in the prevention of TB; such a strategy should be performed mainly among individuals with risk of progression. Progression from LTBI to active TB is highest both in recent contacts of patients with active TB, and in immunocompromised subjects. Therefore, LTBI could either be considered a permanent host defence or, seen from the opposite point of view, it could represent a long-lasting threat if the efficiency of the immune system declines over a lifetime. Interferon gamma release assays (IGRAs) show better sensitivity and specificity than the Mantoux test.

Lipoid pneumonia is an uncommon disorder characterized by accumulation of lipid components into the interstitial and alveolar compartment. The usual classification distinguishes endogenous and exogenous and acute or chronic forms, related to the type of fats, the amount of damage and the time of exposure. We describe a case of exogenous lipoid pneumonia by inhalation of vaseline used for cleaning of the tracheostoma in a 63-year-old female, presenting as cough, worsening dyspnea in few weeks. The diagnosis was finally established with a re-evaluation of BAL with specific staining for lipids, revealing the presence of foamy macrophages lipids rich, according to HRCT findings.

TNFR-associated periodic syndrome is an autoinflammatory disorder caused by autosomal-dominant mutations in TNFRSF1A, the gene encoding for TNFR superfamily 1A. The lack of knowledge in the field of TNFR-associated periodic syndrome biology is clear, particularly in the context of control of immune self-tolerance. We investigated how TNF-α/TNFR superfamily 1A signaling can affect T cell biology, focusing on conventional CD4+CD25− and regulatory CD4+CD25+ T cell functions in patients with TNFR-associated periodic syndrome carrying either high or low penetrance TNFRSF1A mutations. Specifically, we observed that in high penetrance TNFR-associated periodic syndrome, at the molecular level, these alterations were secondary to a hyperactivation of the ERK1/2, STAT1/3/5, mammalian target of rapamycin, and NF-κB pathways in conventional T cells. In addition, these patients had a lower frequency of peripheral regulatory T cells, which also displayed a defective suppressive phenotype. These alterations were partially found in low penetrance TNFR-associated periodic syndrome, suggesting a specific link between the penetrance of the TNFRSF1A mutation and the observed T cell phenotype. Taken together, our data envision a novel role for adaptive immunity in the pathogenesis of TNFR-associated periodic syndrome involving both CD4+ conventional T cells and Tregs, suggesting a novel mechanism of inflammation in the context of autoinflammatory disorders.

Type 1 diabetes is characterized by autoimmune destruction of pancreatic β-cells in genetically susceptible individuals. Triggers of islet autoimmunity, time course, and the precise mechanisms responsible for the progressive β-cell failure are not completely understood. The recent escalation of obesity in affluent countries has been suggested to contribute to the increased incidence of type 1 diabetes. Understanding the link between metabolism and immune tolerance could lead to the identification of new markers for the monitoring of disease onset and progression. We studied several immune cell subsets and factors with high metabolic impact as markers associated with disease progression in high-risk subjects and type 1 diabetic patients at onset and at 12 and 24 months after diagnosis. A multiple correlation matrix among different parameters was evaluated statistically and assessed visually on two-dimensional graphs. Markers to predict residual β-cell function up to 1 year after diagnosis were identified in multivariate logistic regression models. The meta-immunological profile changed significantly over time in patients, and a specific signature that was associated with worsening disease was identified. A multivariate logistic regression model measuring age, BMI, fasting C-peptide, number of circulating CD3+CD16+CD56+ cells, and the percentage of CD1c+CD19−CD14−CD303− type 1 myeloid dendritic cells at disease onset had a significant predictive value. The identification of a specific meta-immunological profile associated with disease status may contribute to our understanding of the basis of diabetes progression.

Leptin is an adipocyte-derived hormone that controls food intake and reproductive and immune functions in rodents. In uncontrolled human studies, low leptin levels are associated with impaired immune responses and reduced T-cell counts; however, the effects of leptin replacement on the adaptive immune system have not yet been reported in the context of randomized, controlled studies and/or in conditions of chronic acquired leptin deficiency. To address these questions, we performed a randomized, double-blinded, placebo-controlled trial of recombinant methionyl-human leptin (metreleptin) administration in replacement doses in women experiencing the female triad (hypothalamic amenorrhea) with acquired chronic hypoleptinemia induced by negative energy balance. Metreleptin restored both CD4 ⁺ T-cell counts and their in vitro proliferative responses in these women. These changes were accompanied by a transcriptional signature in which genes relevant to cell survival and hormonal response were up-regulated, and apoptosis genes were down-regulated in circulating immune cells. We also observed that signaling pathways involved in cell growth/survival/proliferation, such as the STAT3, AMPK, mTOR, ERK1/2, and Akt pathways, were activated directly by acute in vivo metreleptin administration in peripheral blood mononuclear cells and CD4 ⁺ T-cells both from subjects with chronic hypoleptinemia and from normoleptinemic, lean female subjects. Our data show that metreleptin administration, in doses that normalize circulating leptin levels, induces transcriptional changes, activates intracellular signaling pathways, and restores CD4 ⁺ T-cell counts. Thus, metreleptin may prove to be a safe and effective therapy for selective CD4 ⁺ T-cell immune reconstitution in hypoleptinemic states such as tuberculosis and HIV infection in which CD4 ⁺ T cells are reduced.

Bronchial hyperresponsiveness and airway infiltration with eosinophils and T lymphocytes are key features of asthma. In particular, CD4⁺ T cells are currently believed to play a pivotal role as initiators and coordinators of the asthmatic inflammatory response and, therefore, they represent a crucial target of corticosteroid treatment. The aim of the present investigation is thus to evaluate, in patients with mild asthma, the effects of inhaled corticosteroid therapy on the following parameters: (i) functional state of CD4⁺ T cells; (ii) airway eosinophilia; (iii) bronchial hyperresponsiveness to methacholine. The study was completed by twenty asthmatic, atopic subjects, subdivided into two groups of ten and treated for 12 weeks with either inhaled budesonide (200 μg twice daily) or terbutaline alone (500 μg twice daily), respectively. Expression of CD4⁺ T cell activation markers was measured in induced sputum at baseline and after 1, 4, 8 and 12 weeks of treatment by flow cytometry, which showed a down-regulation of HLA-DR and CD25 surface proteins in the budesonide group, compared with the control group; these differences resulted as being statistically significant through weeks 4–12. Budesonide also induced a quick, sharp reduction in the percentage of eosinophils detectable in induced sputum, as well as a more gradual progressive improvement in airway hyperresponsiveness to methacholine. Therefore, in addition to assessing various indices of bronchial inflammation, flow cytometry can be reliably applied to induced sputum in order to monitor, even in mildly symptomatic patients, the effects of anti-asthma treatments on T cell activation.