David B. Corry

Antielastin autoimmunity in tobacco smoking–induced emphysema

Chronic obstructive pulmonary disease and emphysema are common destructive inflammatory diseases that are leading causes of death worldwide. Here we show that emphysema is an autoimmune disease characterized by the presence of antielastin antibody and T-helper type 1 (TH1) responses, which correlate with emphysema severity. These findings link emphysema to adaptive immunity against a specific lung antigen and suggest the potential for autoimmune pathology of other elastin-rich tissues such as the arteries and skin of smokers.

Interleukin 25 promotes the initiation of proallergic type 2 responses

The molecular mechanisms underlying the initiation of innate and adaptive proallergic type 2 responses are not understood. Interleukin (IL) 25, a member of the IL-17 cytokine family, was recently reported (Owyang, A.M., C. Zaph, E.H. Wilson, K.J. Guild, T. McClanahan, H.R. Miller, D.J. Cua, M. Goldschmidt, C.A. Hunter, R.A. Kastelein, and D. Artis. 2006. J. Exp. Med. 203:843–849; Fallon, P.G., S.J. Ballantyne, N.E. Mangan, J.L. Barlow, A. Dasvarma, D.R. Hewett, A. McIlgorm, H.E. Jolin, and A.N. McKenzie. 2006. J. Exp. Med. 203:1105–1116) to be important in Th2 cell–mediated immunity to parasitic infection. However, the cellular source and targets of IL-25 are not well understood. We show that mouse IL-25 is expressed by lung epithelial cells as a result of innate immune responses to allergens. Transgenic overexpression of IL-25 by these cells leads to mucus production and airway infiltration of macrophages and eosinophils, whereas blockade of IL-25 conversely reduces the airway inflammation and Th2 cytokine production in an allergen-induced asthma model. In addition, IL-25, with a receptor more highly expressed in Th2 than other effector T cells, promotes Th2 cell differentiation in an IL-4– and signal transducer and activator of transcription 6–dependent manner. During early T cell activation, IL-25 potentiates expression of the nuclear factor of activated T cells c1 and JunB transcription factors, which possibly results in increased levels of initial IL-4 production, up-regulation of GATA-3 expression, and enhanced Th2 cell differentiation. Thus, IL-25 is a critical factor regulating the initiation of innate and adaptive proallergic responses.

An Immune Basis for Lung Parenchymal Destruction in Chronic Obstructive Pulmonary Disease and Emphysema

ABSTRACT Background Chronic obstructive pulmonary disease and emphysema are a frequent result of long-term smoking, but the exact mechanisms, specifically which types of cells are associated with the lung destruction, are unclear. Methods and Findings We studied different subsets of lymphocytes taken from portions of human lungs removed surgically to find out which lymphocytes were the most frequent, which cell-surface markers these lymphocytes expressed, and whether the lymphocytes secreted any specific factors that could be associated with disease. We found that loss of lung function in patients with chronic obstructive pulmonary disease and emphysema was associated with a high percentage of CD4+ and CD8+ T lymphocytes that expressed chemokine receptors CCR5 and CXCR3 (both markers of T helper 1 cells), but not CCR3 or CCR4 (markers of T helper 2 cells). Lung lymphocytes in patients with chronic obstructive pulmonary disease and emphysema secrete more interferon gamma—often associated with T helper 1 cells—and interferon-inducible protein 10 and monokine induced by interferon, both of which bind to CXCR3 and are involved in attracting T helper 1 cells. In response to interferon-inducible protein 10 and monokine induced by interferon, but not interferon gamma, lung macrophages secreted macrophage metalloelastase (matrix metalloproteinase-12), a potent elastin-degrading enzyme that causes tissue destruction and which has been linked to emphysema. Conclusions These data suggest that Th1 lymphoctytes in the lungs of people with smoking-related damage drive progression of emphysema through CXCR3 ligands, interferon-inducible protein 10, and monokine induced by interferon.

Constructing polycompetitor cDNAs for quantitative PCR

Analysis of mRNA levels using reverse transcription coupled with the polymerase chain reaction provides a powerful tool for studying cytokine regulation in cellular immunology. We report a novel method for cloning competitor cDNAs that is rapid, efficient and inexpensive. By linking multiple competitor cDNAs in tandem, polycompetitor constructs can be created that allow the use of a single reagent for individual PCR assays. Assays can be performed on minute samples of cell culture or tissue and can be reliably quantitated after routine gel electrophoresis without the use of densitometry or labeled nucleotides. The utility of this technique lies in the ability to produce a relatively inexpensive customized reagent that is simple to use and that allows for sensitive determinations of gene expression in a rapid and convenient manner. This method should allow investigators in many areas of biology to easily quantitate a broad range of important regulatory molecules.

Induction and regulation of the IgE response

Immunoglobulin E (IgE) is believed to be one of the major mediators of immediate hypersensitivity reactions that underlie atopic conditions such as urticaria, seasonal allergy, asthma and anaphylaxis. Factors that control IgE production are therefore essential to the pathogenesis of these important afflictions. But a complete understanding of this topic is lacking, while new data have raised questions regarding the precise role of IgE in atopic disease. Evolving concepts of IgE production and elimination are likely to clarify the importance of IgE in health and disease.

A Protease-Activated Pathway Underlying Th Cell Type 2 Activation and Allergic Lung Disease

The respiratory allergens that induce experimental Th cell type 2-dependent allergic lung inflammation may be grouped into two functional classes. One class of allergens, in this study termed type I, requires priming with adjuvants remote from the lung to overcome airway tolerogenic mechanisms that ordinarily preclude allergic responses to inhaled Ags. In contrast, the other, or type II, allergen class requires neither remote priming nor additional adjuvants to overcome airway tolerance and elicit robust allergic lung disease. In this study, we show in an experimental model that diverse type II allergens share in common proteolytic activity that is both necessary and sufficient for overcoming airway tolerance and induction of pulmonary allergic disease. Inactivated protease and protease-free Ag fragments showed no allergenic potency, demonstrating that only active protease acting on endogenous substrates was essential. Furthermore, induction of airway tolerance could be aborted and allergic lung disease established by simply adding purified protease to a type I allergen. Thus, exogenous proteases are common to type II allergens and may be generally required to overcome the innate resistance of the airway to Th cell type 2 activation and allergic inflammation, raising concern for their potential contribution to diseases such as asthma.

Decreased allergic lung inflammatory cell egression and increased susceptibility to asphyxiation in MMP2-deficiency

Clearance of recruited immune cells is necessary to resolve inflammatory reactions. We show here that matrix metalloproteinase 2 (MMP2), as part of an interleukin 13 (IL-13)–dependent regulatory loop, dampens inflammation by promoting the egress of inflammatory cells into the airway lumen. MMP2−/− mice showed a robust asthma phenotype and increased susceptibility to asphyxiation induced by allergens. However, whereas the lack of MMP2 reduced the influx of cells into bronchoalveolar lavage (BAL), numerous inflammatory cells accumulated in the lung parenchyma. BAL of MMP2−/− mice lacked normal chemotactic activity, whereas lung inflammatory cells from the same mice showed appropriate chemotactic responses. Thus, MMP2 establishes the chemotactic gradient required for egression of lung inflammatory cells and prevention of lethal asphyxiation.

Overlapping and independent contributions of MMP2 and MMP9 to lung allergic inflammatory cell egression through decreased CC chemokines

The mechanisms that initiate allergic lung inflammation are relevant to expression of diseases such as asthma, but the factors underlying resolution of inflammation are equally important. Previously, we demonstrated the importance of matrix metalloproteinase 2 (MMP2) for airway egression of lung eosinophils, a critical anti‐inflammatory mechanism without which mice are rendered highly susceptible to lethal asphyxiation. Here we show that leukocyte MMP9 is the dominant airway MMP controlling inflammatory cell egression. The allergic lung phenotype of MMP9−/− mice was similar to WT and was not altered by concomitant deletion of the MMP2 gene (double knockout; dko). However, inflammatory cells accumulated aberrantly in the lungs of allergen‐challenged MMP9−/− and dko mice and fewer eosinophils and neutrophils were present in bronchoalveolar lavage. These aberrant cellular trafficking patterns were explained by disruption of transepithelial chemokine gradients, in MMP2−/− mice affecting only eotaxin (CCL11), but in MMP9−/− and dko mice involving eotaxin, MARC (CCL7), and TARC (CCL17). Thus, by establishing multiple transepithelial chemokine gradients, MMP9 is broadly implicated in the resolution of allergic inflammation, an essential protective mechanism that overlaps with a more limited role played by MMP2.

Absence of the Complement Anaphylatoxin C3a Receptor Suppresses Th2 Effector Functions in a Murine Model of Pulmonary Allergy

Asthma is a chronic inflammatory disease of the lung resulting in airway obstruction. The airway inflammation of asthma is strongly linked to Th2 lymphocytes and their cytokines, particularly IL-4, IL-5, and IL-13, which regulate airway hyperresponsiveness, eosinophil activation, mucus production, and IgE secretion. Historically, complement was not thought to contribute to the pathogenesis of asthma. However, our previous reports have demonstrated that complement contributes to bronchial hyperreactivity, recruitment of airway eosinophils, IL-4 production, and IgE responses in a mouse model of pulmonary allergy. To define the complement activation fragments that mediate these effects, we assessed the role of the complement anaphylatoxin C3a in a mouse model of pulmonary allergy by challenging C3aR-deficient mice intranasally with a mixed Ag preparation of Aspergillus fumigatus cell culture filtrate and OVA. Analysis by plethysmography after challenge revealed an attenuation in airway hyperresponsiveness in C3aR-deficient mice relative to wild-type mice. C3aR-deficient mice also had an 88% decrease in airway eosinophils and a 59% reduction in lung IL-4-producing cells. Consistent with the reduced numbers of IL-4-producing cells, C3aR-deficient mice had diminished bronchoalveolar lavage levels of the Th2 cytokines, IL-5 and IL-13. C3aR knockout mice also exhibited decreases in IgE titers as well as reduced mucus production. Collectively, these data highlight the importance of complement activation, the C3a anaphylatoxin, and its receptor during Th2 development in this experimental model and implicate these molecules as possible therapeutic targets in diseases such as asthma.

Proinflammatory role for let-7 microRNAS in experimental asthma.

MicroRNAs (miRNAs) are short, non-coding RNAs that target and silence protein coding genes through 3′-UTR elements. Evidence increasingly assigns an immunosuppressive role for miRNAs in immunity, but relatively few miRNAs have been studied, and an overall understanding of the importance of these regulatory transcripts in complex in vivo systems is lacking. Here we have applied multiple technologies to globally analyze miRNA expression and function in allergic lung disease, an experimental model of asthma. Deep sequencing and microarray analyses of the mouse lung short RNAome revealed numerous extant and novel miRNAs and other transcript classes. Similar to mRNAs, lung miRNA expression changed dynamically during the transition from the naive to the allergic state, suggesting numerous functional relationships. A possible role for miRNA editing in altering the lung mRNA target repertoire was also identified. Multiple members of the highly conserved let-7 miRNA family were the most abundant lung miRNAs, and we confirmed in vitro that interleukin 13 (IL-13), a cytokine essential for expression for allergic lung disease, is regulated by mmu-let-7a. However, inhibition of let-7 miRNAs in vivo using a locked nucleic acid profoundly inhibited production of allergic cytokines and the disease phenotype. Our findings thus reveal unexpected complexity in the miRNAome underlying allergic lung disease and demonstrate a proinflammatory role for let-7 miRNAs.