For example, the regulator of calcineurin 1 (RCAN1) is a transcription factor that inhibits signal transduction mediated by the nuclear factor of activated T cells (NFAT) [58], and has been shown to reduce inflammatory responses in mice by stabilizing an inhibitor of nuclear factor-kappa B cells (NF-κB) [59]. Two possible causes of secondary immunodeficiency, accelerated ageing and GSK1120212 cost zinc deficiency, have been explored further. Because of the senescence associated to neurological conditions in DS such as premature Alzheimer’s disease [60] a similar ageing process in the immune system has been suggested, including mechanisms of increased apoptosis [61,62], that could be responsible for the observed lymphopenia and

immune dysfunction. The deficiency of plasma zinc levels observed in some DS subjects and the need of zinc for SOD activity have been proposed as mechanisms of immunological abnormalities. Cocchi and colleagues [25] tested

if zinc deficiency might be only transient, and check details found that plasma levels of zinc decrease over time after 5 years of age. However, observational studies examining zinc levels and immune status and clinical trials of zinc supplementation have failed to show a consistent clinical benefit [63–65]. DS children might have symptoms of chronic rhinitis and reactive airway disease, suggesting hypersensitivity to inhaled allergens. A study comparing positivity to skin prick hypersensitivity test between symptomatic DS children and age-matched controls found that 18% of cases had at least one positive allergen in the skin test, which contrasts with 54% of non-DS controls [66]. The authors conclude that allergen sensitization is not a major contributor of respiratory illnesses in DS children. Vestergen et al. [31] found only six of 44 DS

patients with elevated IgE, and none of 28 DS individuals tested had an allergen identified as a trigger for allergy symptoms. Despite the multiple immunological abnormalities outlined above, it is still unclear whether these are the major determinants Protein kinase N1 of increased risk of infections in DS children. This susceptibility to infections is probably enhanced by other co-morbidities that weaken mucosal barriers; for example, abnormal airway and ear anatomy, macroglossia, congenital heart disease and reactive airway disease or an inability to handle secretions. Anatomical abnormalities of the airways may impair clearance of secretions and facilitate infections. Bertrand et al. [67] described airway anomalies among 75% of DS children and 35% of non-DS children with recurrent respiratory symptoms who underwent fibreoptic bronchoscopy. The most common abnormality seen in both DS and non-DS groups was laryngomalacia, with 50% incidence in the DS group compared to 19% in the non-DS group. Tracheomalacia and tracheal bronchus were also observed. Evidence of pulmonary hypoplasia associated to DS has also been reported [68,69].