Macrophages regulate lung ILC2 activation via Pla2g5-dependent mechanisms.

Group V phospholipase A2 (Pla2g5) is a lipid-generating enzyme necessary for macrophage effector functions in pulmonary inflammation. However, the lipid mediators involved and their cellular targets have not been identified. Mice lacking Pla2g5 showed markedly reduced lung ILC2 activation and eosinophilia following repetitive Alternaria Alternata inhalation. While Pla2g5-null mice had Wt levels of immediate IL-33 release after one Alternaria dose, they failed to upregulate IL-33 in macrophages following repeated Alternaria administration. Unexpectedly, while adoptive transfer of bone marrow-derived (BM)-macrophages restored ILC2 activation and eosinophilia in Alternaria-exposed Pla2g5-null mice, exogenous IL-33 did not. Conversely, transfers of Pla2g5-null BM-macrophages reduced inflammation in Alternaria-exposed Wt mice. Mass spectrometry analysis of free fatty acids (FFAs) demonstrated significantly reduced FFAs (including linoleic acid (LA) and oleic acid (OA)) in lung and BM-macrophages lacking Pla2g5. Exogenous administration of LA or LA+OA to Wt mice sharply potentiated IL-33-induced lung eosinophilia and ILC2 expansion in vitro and in vivo. In contrast, OA potentiated IL-33-induced inflammation and ILC2 expansion in Pla2g5-null mice, but LA was inactive both in vivo and in vitro. Notably, Pla2g5-null ILC2s showed significantly reduced expression of the FFA-receptor-1 compared to Wt ILC2s. Thus, macrophage-associated Pla2g5 contributes significantly to type-2 immunity through regulation of IL-33 induction and FFA-driven ILC2 activation.

Differential modulation of mediator release from human basophils and mast cells by mizolastine.

BACKGROUND: Basophils and mast cells play a major role in the pathogenesis of allergic disorders by releasing several proinflammatory mediators. Some histamine H1 receptor antagonists exert anti-inflammatory activities by modulating mediator release from basophils and mast cells. OBJECTIVE: To study the in vitro effects of mizolastine, an H1 receptor antagonist, on the release of eicosanoids, histamine and IL-4 from human basophils and lung mast cells. METHODS AND RESULTS: Mizolastine (10(-7)-10(-5) M) concentration-dependently inhibited the release of cysteinyl leukotriene C4 from anti-IgE-stimulated basophils (IC(50): 3.85+/-0.28 microM) and mast cells (IC(50): 3.92+/-0.41 microM). The same concentrations of mizolastine did not affect anti-IgE-induced prostaglandin D2 release from lung mast cells. In contrast, mizolastine enhanced up to 80% IgE-mediated histamine release (EC(50): 4.63+/-0.14 microM) from basophils, but not from mast cells and it significantly potentiated IL-4 release from basophils induced by anti-IgE. Mizolastine did not affect histamine release from basophils induced by formyl peptide, whereas it inhibited cysteinyl leukotriene C4 release (IC(50): 1.86+/-0.24 microM). Blockade of cytosolic phospholipase A2 and arachidonic acid mobilization by pyrrolidine-1 did not alter the effect of mizolastine on histamine release from basophils, thereby excluding accumulation of arachidonic acid metabolic intermediates as the cause of this effect. Mizolastine did not influence anti-IgE-induced activation of extracellular signal-regulated kinase-1 and -2 (ERK-1 and -2) in human basophils. CONCLUSIONS: Mizolastine efficiently inhibits LTC4 synthesis in human basophils and mast cells presumably by interfering with 5-lipoxygenase. In contrast, it enhances histamine and IL-4 release only from anti-IgE-stimulated basophils. Therefore, mizolastine differentially regulates the production of mediators from basophils and mast cells in a cell- and stimulus-specific fashion.

Abnormal GH receptor signaling in children with idiopathic short stature.

Peripheral GH insensitivity may underlie idiopathic short stature in children. As the clinical and biochemical hallmarks of partial GH insensitivity have not yet been clearly elucidated, the identification of such patients is still difficult. We integrated functional, biochemical, and molecular studies to define the more reliable marker(s) of GH insensitivity. In particular, we measured GH receptor transducing properties through GH-induced protein tyrosine phosphorylation in patients' peripheral blood mononuclear cells and performed direct sequencing analysis of GH receptor-coding exons. Five of 14 idiopathic short stature patients with low basal IGF-I levels showed low or absent IGF-I increment after 4 d of GH administration. However, a prolonged GH stimulation induced in 3 of them an increase in IGF-I 40% above the baseline value. The IGF-binding protein-3 behavior paralleled that of IGF-I. The 2 GH-unresponsive subjects showed an abnormal tyrosine phosphorylation pattern after GH challenge. Sequence analysis of the GH receptor gene revealed a heterozygous mutation resulting in an Arg to Cys change (R161C) in exon 6 in only 1 patient, who had normal GH receptor responsiveness. Our findings indicate that abnormal GH receptor signaling may underlie idiopathic short stature even in the absence of GH receptor mutations. Thus, combining the 4-d IGF-I generation test and the analysis of GH-induced protein tyrosine phosphorylation is a useful tool to help identify idiopathic short stature patients with partial GH insensitivity.

Defective surface expression of attractin on T cells in patients with common variable immunodeficiency (CVID).

The proliferative responses of T lymphocytes of a subset of patients with CVID are abnormally low. This may be due to abnormalities in extracellular interactions or signalling defects downstream from membrane-associated receptors. Demonstrating that the T cell receptor signalling was normal, we observed no abnormal pattern of activation-induced tyrosine phosphorylation in cells from CVID patients. Moreover, the addition of exogenous IL-2 increased the low proliferation to mitogens, thus indicating the integrity of the IL-2R signalling apparatus. Attractin is a rapidly expressed T cell activation antigen involved in forming an association between T cells and monocytes. Twenty-four to 48 h after activation by CD3 cross-linking, attractin expression was not up-regulated on the cells of CVID patients despite normal up-regulation of CD25 and CD26. On control cells, however, attractin expression was up-regulated together with CD25 and CD26. The addition of the purified 175-kD attractin was capable of restoring the proliferative response of peripheral blood mononuclear cells following CD3 X-L in the presence of suboptimal concentrations of rIL-2 (10 and 20 U/ml). The effect was dose-dependent with the maximal effect at a concentration of 500 ng/ml, and present at a concentration as low as 50 ng/ml. Due to the likely role of attractin in cell guidance and amplification of the immune response, our results indicate that the lack of up-regulation of the molecule in patients with CVID may in turn affect any further step of productive immune response. Our finding may also imply a potential therapeutic role for this novel molecule.

Chronic unexplained liver disease in children with primary immunodeficiency syndromes.

Liver disease may be found in patients with primary immunodeficiency syndromes because of the high risk of infection with hepatotropic viruses related to the treatment with blood derivatives. The prevalence of liver disease in these patients and its etiology, however, is still not completely understood. We have evaluated the prevalence and the etiology of liver disease in children with different forms of primary immunodeficiencies. Thirty patients included in the study underwent molecular studies to detect common hepatotropic viruses, including hepatitis C and G viruses. Liver involvement was found in 11 of 30 (36.6%) patients. All patients with liver disease had deficiencies of specific immunity, with a prevalence in this subgroup of 47.8%. Liver disease was more severe in patients with T and B cell combined immune disorders than in those with a selective T cell immunodeficiency. Moreover, the severity of the disease correlated with an overall more rapid fatal outcome. A viral etiology was found in only six of these patients, whereas in the remaining five patients, no cause of liver injury was identified. In the virally infected patients, hepatitis C virus was the most common viral agent. In patients with immunodeficiencies, there is a high prevalence of liver disease not fully explained on the basis of the common viral infections.

Enhancement of carrageenin foot oedema by 1,10 -phenanthroline and evidence for the bradykinin as endogenous mediator.

Carrageenin oedema in enhanced by the simultaneous injection in the rat paw of 1,10-phenanthroline, a kininase inhibitor. The analysis of the time-course of this enhancement showed that the maximal effect was observed about 3 hours after the injection. This enhancement was also present when the oedema-producing agent was cellulose sulphate, a kinin-releasing compound. On the contrary, oedema induced by eggwhite as well as by dextran, which are mainly mediated by histamine and 5-hydroxytryptamine, were unaffected by 1,10-phenanthroline. These results further support the role of kinins in the pathogenesis of carrageenin oedema.