Immunoglobulin (Ig) genes are hypermutated in B lymphocytes that are the precursors to memory B cells. The mutations are linked to transcription initiation, but non-Ig promoters are permissible for the mutation process; thus, other genes expressed in mutating B cells may also be subject to somatic hypermutation. Significant mutations were not observed in c- MYC , S14 , or α-fetoprotein ( AFP ) genes, but BCL-6 was highly mutated in a large proportion of memory B cells of normal individuals. The mutation pattern was similar to that of Ig genes.

Phosphoinositide 3-kinase (PI3K) is thought to contribute to the pathogenesis of asthma by effecting the recruitment, activation, and apoptosis of inflammatory cells. We examined the role of class IA PI3K in antigen-induced airway inflammation and hyperresponsiveness by i.p. administration into mice of Δp85 protein, a dominant negative form of the class IA PI3K regulatory subunit, p85α, which was fused to HIV-TAT (TAT-Δp85). Intraperitoneal administration of TAT-Δp85 caused time-dependent transduction into blood leukocytes, and inhibited activated phosphorylation of protein kinase B (PKB), a downstream target of PI3K, in lung tissues in mice receiving intranasal FMLP. Antigen challenge elicited pulmonary infiltration of lymphocytes, eosinophils and neutrophils, increase in mucus-containing epithelial cells, and airway hyperresponsiveness to methacholine. Except for modest airway neutrophilia, these effects all were blocked by treatment with 3–10 mg/kg of TAT-Δp85. There was also significant reduction in IL-5 and IL-4 secretion into the BAL. Intranasal administration of IL-5 caused eosinophil migration into the airway lumen, which was attenuated by systemic pretreatment with TAT-Δp85. We conclude that PI3K has a regulatory role in Th2-cell cytokine secretion, airway inflammation, and airway hyperresponsiveness in mice.

Acute lung injury (ALI) is a hallmark of systemic inflammation associated with high mortality. Although the vitamin D receptor (VDR) is highly expressed in the lung, its role in lung physiology remains unclear. We investigated the effect of VDR deletion on ALI using a lipopolysaccharide (LPS)-induced sepsis model. After LPS challenge VDR-null mice exhibited more severe ALI and higher mortality compared with wild-type (WT) counterparts, manifested by increased pulmonary vascular leakiness, pulmonary edema, apoptosis, neutrophil infiltration, and pulmonary inflammation, which was accompanied by excessive induction of angiopoietin (Ang)-2 and myosin light chain (MLC) phosphorylation in the lung. 1,25-Dihydroxyvitamin D blocked LPS-induced Ang-2 expression by blocking nuclear factor-κB activation in human pulmonary artery endothelial cells. The severity of lung injury seen in VDR-null mice was ameliorated by pretreatment with L1–10, an antagonist of Ang-2, suggesting that VDR signaling protects the pulmonary vascular barrier by targeting the Ang-2-Tie-2-MLC kinase cascade. Severe ALI in VDR-null mice was also accompanied by an increase in pulmonary renin and angiotensin II levels, and pretreatment of VDR-null mice with angiotensin II type 1 receptor blocker losartan partially ameliorated the severity of LPS-induced lung injury. Taken together, these observations provide evidence that the vitamin D-VDR signaling prevents lung injury by blocking the Ang-2-Tie-2-MLC kinase cascade and the renin-angiotensin system.

Background: Since mid-December 2019, a cluster of pneumonia-like diseases caused by a novel coronavirus, now designated COVID-19 by the WHO, emerged in Wuhan city and rapidly spread throughout China. Here we identify the clinical characteristics of COVID-19 in a cohort of patients in Shanghai. Methods: Cases were confirmed by real-time RT-PCR and were analysed for demographic, clinical, laboratory and radiological features. Results: Of 198 patients, the median duration from disease onset to hospital admission was 4 days. The mean age of the patients was 50.1 years, and 51.0% patients were male. The most common symptom was fever. Less than half of the patients presented with respiratory systems including cough, sputum production, itchy or sore throat, shortness of breath, and chest congestion. 5.6% patients had diarrhoea. On admission, T lymphocytes were decreased in 45.8% patients. Ground glass opacity was the most common radiological finding on chest computed tomography. 9.6% were admitted to the ICU because of the development of organ dysfunction. Compared with patients not treated in ICU, patients treated in the ICU were older, had longer waiting time to admission, fever over 38.5° C, dyspnoea, reduced T lymphocytes, elevated neutrophils and organ failure. Conclusions: In this single centre cohort of COVID-19 patients, the most common symptom was fever, and the most common laboratory abnormality was decreased blood T cell counts. Older age, male, fever over 38.5°C, symptoms of dyspnoea, and underlying comorbidity, were the risk factors most associated with severity of disease.

We reported previously that exogenously added human group V phospholipase A₂(hVPLA₂) could elicit leukotriene B₄(LTB₄) biosynthesis in human neutrophils (Han, S. K., Kim, K. P., Koduri, R., Bittova, L., Munoz, N. M., Leff, A. R., Wilton, D. C., Gelb, M. H., and Cho, W. (1999) J. Biol. Chem. 274, 11881–11888). To determine the mechanism of the hVPLA₂-induced LTB₄biosynthesis in neutrophils, we thoroughly examined the effects of hVPLA₂ and their lipid products on the activity of group IVA cytosolic PLA₂ (cPLA₂) and LTB₄biosynthesis under different conditions. As low as 1 nmexogenous hVPLA₂ was able to induce the release of arachidonic acid (AA) and LTB₄. Typically, AA and LTB₄ were released in two phases, which were synchronized with a rise in intracellular calcium concentration ([Ca²⁺]_i) near the perinuclear region and cPLA₂ phosphorylation. A cellular PLA₂ assay showed that hVPLA₂ acted primarily on the outer plasma membrane, liberating fatty acids and lysophosphatidylcholine (lyso-PC), whereas cPLA₂ acted on the perinuclear membrane. Lyso-PC and polyunsaturated fatty acids including AA activated cPLA₂ and 5-lipoxygenase by increasing [Ca²⁺]_i and inducing cPLA₂ phosphorylation, which then led to LTB₄biosynthesis. The delayed phase was triggered by the binding of secreted LTB₄ to the cell surface LTB₄receptor, which resulted in a rise in [Ca²⁺]_i and cPLA₂phosphorylation through the activation of mitogen-activated protein kinase, extracellular signal-regulated kinase 1/2. These results indicate that a main role of exogenous hVPLA₂ in neutrophil activation and LTB₄ biosynthesis is to activate cPLA₂ and 5-lipoxygenase primarily by liberating from the outer plasma membrane lyso-PC that induces [Ca²⁺]_i increase and cPLA₂ phosphorylation and that hVPLA₂-induced LTB₄ production is augmented by the positive feedback activation of cPLA₂ by LTB₄.

We previously reported that exogenously added human group V phospholipase A₂ (hVPLA₂) could elicit leukotriene B₄ biosynthesis in human neutrophils through the activation of group IVA phospholipase A₂ (cPLA₂) (Kim, Y. J., Kim, K. P., Han, S. K., Munoz, N. M., Zhu, X., Sano, H., Leff, A. R., and Cho, W. (2002) J. Biol. Chem. 277, 36479-36488). In this study, we determined the functional significance and mechanism of the exogenous hVPLA₂-induced arachidonic acid (AA) release and leukotriene C₄ (LTC₄) synthesis in isolated human peripheral blood eosinophils. As low a concentration as 10 nm exogenous hVPLA₂ was able to elicit the significant release of AA and LTC₄ from unstimulated eosinophils, which depended on its ability to act on phosphatidylcholine membranes. hVPLA₂ also augmented the release of AA and LTC₄ from eosinophils activated with formyl-Met-Leu-Phe + cytochalasin B. A cellular fluorescent PLA₂ assay showed that hVPLA₂ had a lipolytic action first on the outer plasma membrane and then on the perinuclear region. hVPLA₂ also caused the translocation of 5-lipoxygenase from the cytosol to the nuclear membrane and a 2-fold increase in 5-lipoxygenase activity. However, hVPLA₂ induced neither the increase in intracellular calcium concentration nor cPLA₂ phosphorylation; consequently, cPLA₂ activity was not affected by hVPLA₂. Pharmacological inhibition of cPLA₂ and the hVPLA₂-induced activation of eosinophils derived from the cPLA₂-deficient mouse corroborated that hVPLA₂ mediates the release of AA and leukotriene in a cPLA₂-independent manner. As such, this study represents a unique example in which a secretory phospholipase induces the eicosanoid formation in inflammatory cells, completely independent of cPLA₂ activation.