A. Barry Kay

Anti-IL-5 treatment reduces deposition of ECM proteins in the bronchial subepithelial basement membrane of mild atopic asthmatics

Eosinophil-derived TGF-beta has been implicated in remodeling events in asthma. We hypothesized that reduction of bronchial mucosal eosinophils with anti-IL-5 would reduce markers of airway remodeling. Bronchial biopsies were obtained before and after three infusions of a humanized, anti-IL-5 monoclonal antibody (mepolizumab) in 24 atopic asthmatics in a randomized, double-blind, placebo-controlled study. The thickness and density of tenascin, lumican, and procollagen III in the reticular basement membrane (RBM) were quantified immunohistochemically by confocal microscopy. Expression of TGF-beta1 mRNA by airway eosinophils was assessed by in situ hybridization, and TGF-beta1 protein was measured in bronchoalveolar lavage (BAL) fluid by ELISA. At baseline, airway eosinophil infiltration and ECM protein deposition was increased in the RBM of asthmatics compared with nonasthmatic controls. Treating asthmatics with anti-IL-5 antibody, which specifically decreased airway eosinophil numbers, significantly reduced the expression of tenascin, lumican, and procollagen III in the bronchial mucosal RBM when compared with placebo. In addition, anti-IL-5 treatment was associated with a significant reduction in the numbers and percentage of airway eosinophils expressing mRNA for TGF-beta1 and the concentration of TGF-beta1 in BAL fluid. Therefore eosinophils may contribute to tissue remodeling processes in asthma by regulating the deposition of ECM proteins.

Activation of CD4+ T cells, increased TH2-type cytokine mRNA expression, and eosinophil recruitment in bronchoalveolar lavage after allergen inhalation challenge in patients with atopic asthma

BACKGROUND We have examined whether the local eosinophilia provoked by inhalational allergen challenge of patients with atopic asthma is associated with the appearance, in vivo, of activated TH2-type T helper lymphocytes. METHODS Fifteen patients with atopic asthma had bronchial wash and bronchoalveolar lavage (BAL) 24 hours after allergen or diluent challenge separated by at least 21 days. RESULTS There was an increase in eosinophils in both bronchial wash (p = 0.01) and BAL (p = 0.02) after allergen challenge but not after diluent challenge. Activation of CD4+ BAL T cells was suggested by an increase in the expression of CD25 shown by flow cytometry after allergen challenge, when compared with diluent (p = 0.02). There was no evidence of activation of CD8 T cells. By in situ hybridization after allergen challenge as compared with diluent, increases were shown in the numbers of cells expressing mRNA for interleukin-4 (IL-4) (p = 0.005), IL-5 (p = 0.01), and granulocyte-macrophage colony-stimulating factor (p = 0.03) but not IL-3, IL-2, or interferon-gamma. In situ hybridization of BAL cells after immunomagnetic separation of CD2-positive and CD2-negative cell populations showed that IL-4 and IL-5 mRNAs were associated with T lymphocytes after allergen challenge. BAL and bronchial wash eosinophilia closely correlated with maximal late fall in forced expiratory volume in 1 second after allergen challenge. CONCLUSION Cytokines produced by activated TH2-type CD4+ T cells in the airway may contribute to late asthmatic responses by mechanisms that include eosinophil accumulation.

Eosinophils: Biological Properties and Role in Health and Disease

Eosinophils are pleiotropic multifunctional leukocytes involved in initiation and propagation of diverse inflammatory responses, as well as modulators of innate and adaptive immunity. In this review, the biology of eosinophils is summarized, focusing on transcriptional regulation of eosinophil differentiation, characterization of the growing properties of eosinophil granule proteins, surface proteins and pleiotropic mediators, and molecular mechanisms of eosinophil degranulation. New views on the role of eosinophils in homeostatic function are examined, including developmental biology and innate and adaptive immunity (as well as their interaction with mast cells and T cells) and their proposed role in disease processes including infections, asthma, and gastrointestinal disorders. Finally, strategies for targeted therapeutic intervention in eosinophil‐mediated mucosal diseases are conceptualized.

The immunopathology of extrinsic (atopic) and intrinsic (non-atopic) asthma: more similarities than differences

Abstract Intrinsic asthma shows no clinical or serological evidence of IgE-mediated allergy to common environmental agents. Similar to extrinsic asthma, bronchial biopsies from such patients show enhanced expression of Th2-type cytokines, CC chemokines and Iϵ/Cϵ compared with controls. These findings suggest there might be local IgE production directed against unknown antigens, possibly of viral origin or even autoantigens, in this important clinically distinct variant of the disease.

Eosinophils: biology and role in disease.

Publisher Summary The chapter reviews recent findings on the biology of the eosinophil, particularly distinctive eosinophil features, and discusses the possible role of the eosinophil in the pathogenesis of certain diseases with which the cell is associated. There is evidence that eosinophils slow the rate of progression of solid tumors through tumoricidal mechanisms. There is no experiment of nature in that cell, or its progenitors are selectively depleted; and at the present time no pharmacological or biological inhibitor is available for laboratory-based or clinical studies. However, in the past few years, evidence has shifted away from the cell having anti-allergic properties, and even its role in adaptive immunity to helminth infections is seriously questioned. It is important to bear in mind that the eosinophil is an inflammatory cell and that the purpose of inflammation is to restore, repair, and remodel injured tissue. The role of the eosinophil in wound healing has recently received considerable attention, and it seems reasonable to expect that this will be a growth area for eosinophil biologists. Intriguingly, there is now some firm data to implicate the eosinophil in immunological responses against cancer cells. The recent findings on the potential of eosinophils in cancer immunity may stimulate a better understanding of the role of this cell type. It can be stated with reasonable assurity that the eosinophil probably has some homeostatic function in certain physiological situations and that this needs to be considered further.

Peptide immunotherapy in allergic asthma generates IL-10–dependent immunological tolerance associated with linked epitope suppression

Treatment of patients with allergic asthma using low doses of peptides containing T cell epitopes from Fel d 1, the major cat allergen, reduces allergic sensitization and improves surrogate markers of disease. Here, we demonstrate a key immunological mechanism, linked epitope suppression, associated with this therapeutic effect. Treatment with selected epitopes from a single allergen resulted in suppression of responses to other (“linked”) epitopes within the same molecule. This phenomenon was induced after peptide immunotherapy in human asthmatic subjects and in a novel HLA-DR1 transgenic mouse model of asthma. Tracking of allergen-specific T cells using DR1 tetramers determined that suppression was associated with the induction of interleukin (IL)-10+ T cells that were more abundant than T cells specific for the single-treatment peptide and was reversed by anti–IL-10 receptor administration. Resolution of airway pathophysiology in this model was associated with reduced recruitment, proliferation, and effector function of allergen-specific Th2 cells. Our results provide, for the first time, in vivo evidence of linked epitope suppression and IL-10 induction in both human allergic disease and a mouse model designed to closely mimic peptide therapy in humans.

Expression of endothelial and leukocyte adhesion molecules intercellular adhesion molecule-1, E-selectin, and vascular cell adhesion molecule-1 in the bronchial mucosa in steady-state and allergen-induced asthma

BACKGROUND Interactions between cell adhesion molecules and their ligands are an integral part of inflammatory processes and may have direct relevance to the pathology of asthma. METHODS Immunostaining with antibodies to cell adhesion molecules was performed on bronchial biopsy specimens from persons with intrinsic and extrinsic asthma, normal nonasthmatic control subjects, and patients with asthma after allergen challenge. RESULTS There was constitutive expression of intercellular adhesion molecule-1 (ICAM-1), E-selectin and vascular cell adhesion molecule-1 (VCAM-1) in patients with intrinsic and extrinsic asthma and in control subjects. Compared with control subjects, ICAM-1 and E-selectin staining in the submucosa was greater in the intrinsic asthmatic group for intensity (p < 0.02, p < 0.05) and extent (p < 0.01, p < 0.05) of staining, respectively. No differences were observed between patients with extrinsic asthma and normal control subjects, and VCAM-1 expression did not differ among the groups. Epithelial expression of ICAM-1 was more frequent in patients with asthma compared with normal control subjects (p < 0.05). Compared with diluent challenge, bronchial biopsy specimens obtained 24 hours after allergen challenge revealed no significant differences in intensity or extent of staining for ICAM-1, E-selectin, or VCAM-1. After allergen challenge, the intensity and extent of both VCAM-1 and ICAM-1 expression correlated significantly with the number of eosinophils (cells positive for major basic protein). Epithelial ICAM-1 expression was more frequently observed after allergen challenge than after diluent challenge (p < 0.02). CONCLUSIONS The data suggest a complex pattern of regulation for ICAM-1, E-selectin, and VCAM-1 in vivo, where they may reflect the degree of ongoing inflammation in asthma.

Allergen-Derived T Cell Peptide-Induced Late Asthmatic Reactions Precede the Induction of Antigen-Specific Hyporesponsiveness in Atopic Allergic Asthmatic Subjects

Allergen-derived peptides can induce T cell tolerance in naive and Ag-primed mice. This is preceded by transient T cell activation. In humans, intradermal administration of short allergen-derived T cell peptide epitopes provokes IgE-independent isolated late asthmatic reactions (LARs) in sensitized subjects. In this study, we determine whether, as in mouse models, such peptides produce hyporesponsiveness to rechallenge with peptides, or whole allergen, either clinically or in terms of in vitro T cell responses. We found that a second injection of cat allergen (Fel d 1)-derived T cell peptides was associated with a marked reduction, or absence, of the LAR, and that up to 40 wk was required for return to baseline values. The cutaneous late-phase reaction to whole cat dander was also inhibited, even in subjects who did not experience an initial LAR. These observations were associated with a significant decrease in peptide- and whole allergen-induced proliferation of PBMCs and the production of IL-4, IL-13, and IFN-γ in cultures. Thus, allergen-derived peptides induce tolerance to subsequent peptide injection in the target organ (the lung), reduce late-phase cutaneous responsiveness to whole allergen, and alter in vitro T cell reactivity.

Basophils, eosinophils, and mast cells in atopic and nonatopic asthma and in late-phase allergic reactions in the lung and skin☆☆☆★

BACKGROUND Previous studies used indirect methods to identify basophils in the bronchi in asthma, and the numbers were not compared with eosinophils and mast cells. Furthermore, differences in basophil numbers between atopic and nonatopic asthma at baseline and between late-phase skin and asthmatic reactions have not been previously documented. OBJECTIVE The basophil granule-specific mAb BB1 was used to identify basophils in (1) bronchial biopsy specimens from atopic asthmatic subjects and nonatopic asthmatic subjects and control subjects, (2) biopsy specimens from atopic asthmatic subjects before and after inhalational allergen challenge, and (3) late-phase skin reactions. Basophil numbers were compared with EG2(+) eosinophils and tryptase(+) mast cells. METHODS Cells were enumerated in bronchial and skin biopsy specimens by means of immunohistochemistry with the alkaline phosphatase-antialkaline phosphatase method. RESULTS There were elevated numbers of basophils in baseline biopsy specimens in atopic asthmatic subjects compared with atopic control subjects or normal control subjects, although eosinophils and mast cells were 10-fold higher. There was an intermediate number of basophils in nonatopic asthmatic subjects. Basophils increased after allergen inhalation, but again basophils were less than 10% of eosinophils. In contrast, basophils in cutaneous late-phase reactions were approximately 40% of infiltrating eosinophils. The peak of basophil accumulation was at 24 hours, whereas maximal eosinophil infiltration occurred at 6 hours. One third of cutaneous basophils had morphologic appearances suggestive of degranulation. CONCLUSION Numerous basophils infiltrated cutaneous late-phase reactions in atopic subjects. However, this cell was not prominent in bronchial biopsy specimens of asthmatic subjects, either at baseline or after allergen challenge.

Randomised, dose-ranging, placebo-controlled study of chimeric antibody to CD4 (keliximab) in chronic severe asthma

BACKGROUND There is substantial circumstantial evidence that CD4 lymphocytes have a role in the pathogenesis of chronic asthma. We investigated the efficacy and safety in severe corticosteroid-dependent asthma of a single intravenous infusion of keliximab (IDEC CE9.1), a chimeric monoclonal antibody to CD4. METHODS 22 patients were recruited from two asthma clinics. In an ascending-dose design, the first eight patients were assigned 0.5 mg/kg keliximab (six) or placebo (two); the next seven were assigned 1.5 mg/kg (five) or placebo (two); and the last seven were assigned 3.0 mg/kg (five) or placebo (two). Masked data on safety for each dose group were assessed before progression to the next dose. Patients kept a daily symptom diary and measured morning and evening peak expiratory flow (PEF) at home. PEF and forced expiratory volume in 1 s (FEV1) were measured at follow-up clinic visits. FINDINGS Patients given 0.5 mg/kg or 1.5 mg/kg keliximab and placebo recipients did not differ in change from baseline of PEF, FEV1, or symptom score. Those given 3.0 mg/kg keliximab differed significantly from placebo recipients in change in morning PEF (median area under curve [AUC] 445 vs -82.5, p=0.005) and evening PEF (median AUC 548 vs -85, p=0.014). Symptom score showed the same pattern (though differences did not achieve significance), but there was no difference in clinic FEV1. There were no serious adverse effects related to treatment. Two patients had mild exacerbations of eczema and one developed a transient maculopapular rash. All doses of keliximab were associated with a reduction from baseline in CD4 count. INTERPRETATION Our findings raise the possibility that T-cell-directed treatment may be an alternative approach to the treatment of severe asthma.