CCL17/thymus and activation-regulated chemokine induces calcitonin gene-related peptide in human airway epithelial cells through CCR4.

BACKGROUND: Calcitonin gene-related peptide (CGRP) is a potent arterial and venous vasodilator. Increased airway epithelial cell expression of CGRP, together with increased CCL17 expression, was previously observed in a model of provoked asthma in atopic human subjects. OBJECTIVE: We sought to determine whether CCL17 induces CCR4-dependent CGRP synthesis and secretion by human airway epithelial cells. METHODS: Human airway epithelial cell lines (BEAS-2B and A549) and human primary airway cells were cultured with CCL17 or various other cytokines, and CGRP expression was measured by using RT-PCR, quantitative immunofluorescence, and enzyme immunoassay. CCR4 expression was determined in cultured cells by using flow cytometry and in bronchial biopsy specimens by using immunohistochemistry. RESULTS: CCL17 induced a several thousand-fold increase in CGRP mRNA expression and released peptide product from BEAS-2B and A549 cells in a time- and concentration-dependent fashion. Concentration-dependent CCL17-induced release of CGRP by primary human airway epithelial cells was also observed. Under comparable conditions, CCL17 induced greater CGRP release from BEAS-2B cells than either IL-13, a cytokine mixture (TNF-α, GM-CSF, and IL-1), or CCL22. CCR4 was expressed by BEAS-2B and A549 cells and internalized after ligation with CCL17. CCL17-induced CGRP release was inhibited by a specific anti-CCR4 blocking antibody. Bronchial biopsy specimens obtained from healthy volunteers and asthmatic patients before and after provoked asthma all exhibited CCR4 staining of equivalent intensity, indicating that the receptor is constitutively expressed. CONCLUSIONS: CCL17-induced, CCR4-dependent release of CGRP by human airway epithelial cells represents a novel inflammatory pathway and a possible target in patients with asthma and allergic disease.

Calcitonin gene-related peptide- and vascular endothelial growth factor-positive inflammatory cells in late-phase allergic skin reactions in atopic subjects.

BACKGROUND: Allergen-induced late-phase skin reactions are characterized by erythema and edema, but the vasoactive mediators involved remain unclear. Limited evidence from human studies suggests that calcitonin gene-related peptide (CGRP) and vascular endothelial growth factor (VEGF), potent vasodilator and permeability factors, respectively, are expressed by infiltrating inflammatory cells in certain allergic tissue reactions. OBJECTIVE: We sought to determine whether tissue swelling in allergen-challenged skin sites in atopic subjects is associated with the infiltration of CGRP(+) and VEGF(+) inflammatory cells. METHODS: Skin biopsy specimens were obtained from atopic subjects at various times after cutaneous allergen challenge and studied by means of single and double immunohistochemistry and in situ hybridization. RESULTS: CGRP-immunoreactive and CGRP mRNA-positive cell numbers were increased in biopsy specimens from sites of late-phase skin reactions compared with those at the control site (P = .03 and P = .03, respectively). Their numbers paralleled the development and resolution of the edematous late-phase skin reaction, both peaking at 6 hours after allergen challenge. The majority of CGRP-immunoreactive cells were neutrophils and CD3(+) cells, whereas eosinophils were CGRP negative. VEGF-immunopositive cell numbers were also increased in 6-hour biopsy specimens from late-phase skin reactions compared with those seen at control sites (P = .001) with a lesser but significant response (P = .008) at 24 hours. VEGF(+) cells were largely eosinophils, neutrophils, and CD68(+) macrophages. CONCLUSIONS: Late-phase skin reactions in atopic subjects were associated with the infiltration of inflammatory cells expressing CGRP and VEGF, suggesting that these vasoactive factors might play a role in the erythema and edema characteristic of allergic inflammation. They could also be considered targets in attempts to control allergic inflammation.

Development and preliminary clinical evaluation of a peptide immunotherapy vaccine for cat allergy.

BACKGROUND: Allergic sensitization to cat allergens is common and represents a major risk factor for asthma. Specific immunotherapy (SIT) is effective but cumbersome and associated with IgE-dependent adverse events. Immunotherapy targeting allergen-specific T cells, with synthetic peptides representing T-cell epitopes, might improve safety and reduce the duration of treatment. OBJECTIVE: We sought to define major T-cell epitopes of Fel d 1 for peptide immunotherapy, generate a peptide vaccine, and evaluate its safety and tolerability in subjects with cat allergy. METHODS: We determined the binding affinities of Fel d 1 peptides for 10 commonly expressed HLA-DR molecules. Functionally immunodominant peptides were identified by means of proliferation and cytokine secretion. Histamine-releasing activity was assessed, and a peptide vaccine was formulated. Safety and tolerability were evaluated in a dose-ranging phase IIa clinical trial. RESULTS: MHC-binding sequences were identified throughout Fel d 1. Some regions contained multiple overlapping T-cell epitopes that bound multiple MHC molecules. Immunodominant sequences were identified on the basis of proliferative and cytokine (IFN-γ, IL-10, and IL-13) responses. Cat allergen extract, but not peptides, induced histamine release in blood basophils. A single administration of peptide vaccine was safe and well tolerated. The dose of vaccine resulting in the greatest inhibition of the late-phase skin response to intradermal whole allergen challenge was 3 nmol. CONCLUSIONS: Fel d 1 contains multiple overlapping MHC-binding motifs. A peptide vaccine comprising the immunodominant regions of the allergen was safe and well tolerated when given to subjects with cat allergy as a single dose. The dose of vaccine resulting in the greatest reduction in late-phase skin response was defined for future clinical development.

Allergen-induced expression of IL-25 and IL-25 receptor in atopic asthmatic airways and late-phase cutaneous responses.

BACKGROUND: IL-25 is thought to participate in allergic inflammation by propagating T(h)2-type responses. OBJECTIVE: To address the hypothesis that allergen provocation increases expression of IL-25 and its receptor IL-25R in the asthmatic bronchial mucosa and skin dermis of atopic subjects. METHODS: Sequential single and double immunostaining was used to evaluate the numbers and phenotypes of IL-25 and IL-25R immunoreactive cells in bronchial biopsies from mild atopic subjects with asthma (n = 10) before and 24 hours after allergen inhalation challenge and skin biopsies from atopic subjects (n = 10) up to 72 hours after allergen subepidermal injection. RESULTS: IL-25 immunoreactivity was expressed by a majority of epidermal cells in both organs at baseline and was not further augmented by challenge. IL-25R immunoreactive cells were rare in the epidermis before or after challenge. Allergen challenge was associated with significantly (P < .01) increased expression of IL-25 and IL-25R immunoreactivity in the submucosa of both organs. IL-25 immunoreactivity colocalized with eosinophils, mast cells, and endothelial cells, whereas IL-25R immunoreactivity colocalized with eosinophils, mast cells, endothelial cells, and T lymphocytes. In both organs, correlations were observed between increases in IL-25 expression and the magnitudes of the late-phase allergen-induced clinical responses. CONCLUSION: Allergen provocation induces functionally relevant, increased expression of IL-25 and its receptor in the asthmatic bronchial mucosa and dermis of sensitized atopic subjects. In addition to T cells, eosinophils, mast cells, and endothelial cells are potential sources and targets of IL-25 in the course of allergic inflammation.

Expression of functional receptor activity modifying protein 1 by airway epithelial cells with dysregulation in asthma.

BACKGROUND: Epithelial cell expression of calcitonin gene-related peptide (CGRP) is a feature of provoked asthma. Receptor activity modifying protein 1 (RAMP1) and the calcitonin receptor-like receptor combine to form the CGRP1 receptor. OBJECTIVE: To determine whether functional RAMP1 is expressed by airway epithelial cells and whether there are alterations in asthma. METHODS: BEAS-2B and A549 cells lines were studied by RT-PCR, confocal microscopy, a quantitative immunofluorescence assay, and ELISA. Bronchial biopsies from normal subjects and subjects with asthma were examined by immunohistochemistry and in situ hybridization. RESULTS: Inflammatory cytokines induced CGRP release and CGRP mRNA in BEAS-2B and A549 epithelial cell lines. RAMP1 was highly expressed by resting, unstimulated BEAS-2B and A549 cells. CGRP induced internalization of RAMP1 and IL-6 production, both of which were inhibited by the CGRP antagonist, CGRP(8-37). Activation of BEAS-2B and A549 cells by inflammatory cytokines induced CGRP secretion, binding of CGRP to RAMP1, and RAMP1 internalization, which was blocked by CGRP (8-37). RAMP1 immunoreactivity and RAMP1 mRNA expression in bronchial biopsies from subjects with asthma were significantly lower than in normal subjects (P = .002 and P = .007, respectively). Inhalational challenge of atopic subjects with asthma with allergen-derived peptides produced a significant decrease in the numbers of RAMP1-positive epithelial cells in responders (P = .027) but not nonresponders. CONCLUSION: Receptor activity modifying protein 1 was expressed both by airway epithelial cells in culture and in bronchial biopsies from normal subjects and internalized after epithelial cell activation through autocrine feedback of CGRP. There is an apparent dysregulation of RAMP1 in asthmatic epithelium, suggesting continuous stimulation of pathways involving CGRP.

Bone morphogenetic protein (BMP)-4 and BMP-7 regulate differentially transforming growth factor (TGF)-beta1 in normal human lung fibroblasts (NHLF).

BACKGROUND: Airway remodelling is thought to be under the control of a complex group of molecules belonging to the transforming growth factor (TGF)-superfamily. The bone morphogenetic proteins (BMPs) belong to this family and have been shown to regulate fibrosis in kidney and liver diseases. However, the role of BMPs in lung remodelling remains unclear. BMPs may regulate tissue remodelling in asthma by controlling TGF-beta-induced profibrotic functions in lung fibroblasts. METHODS: Cell cultures were exposed to TGF-beta1 alone or in the presence of BMP-4 or BMP-7; control cultures were exposed to medium only. Cell proliferation was assessed by quantification of the incorporation of [3H]-thymidine. The expression of the mRNA encoding collagen type I and IV, tenascin C and fibronectin in normal human lung fibroblasts (NHLF) was determined by real-time quantitative PCR and the main results were confirmed by ELISA. Cell differentiation was determined by the analysis of the expression of alpha-smooth muscle actin (alpha-SMA) by western blot and immunohistochemistry. The effect on matrix metalloproteinase (MMP) activity was assessed by zymography. RESULTS: We have demonstrated TGF-beta1 induced upregulation of mRNAs encoding the extracellular matrix proteins, tenascin C, fibronectin and collagen type I and IV when compared to unstimulated NHLF, and confirmed these results at the protein level. BMP-4, but not BMP-7, reduced TGF-beta1-induced extracellular matrix protein production. TGF-beta1 induced an increase in the activity of the pro-form of MMP-2 which was inhibited by BMP-7 but not BMP-4. Both BMP-4 and BMP-7 downregulated TGF-beta1-induced MMP-13 release compared to untreated and TGF-beta1-treated cells. TGF-beta1 also induced a myofibroblast-like transformation which was partially inhibited by BMP-7 but not BMP-4. CONCLUSIONS: Our study suggests that some regulatory properties of BMP-7 may be tissue or cell type specific and unveil a potential regulatory role for BMP-4 in the regulation of lung fibroblast function.

Activin and transforming growth factor-beta signaling pathways are activated after allergen challenge in mild asthma.

BACKGROUND: Both transforming growth factor (TGF)-beta(1) and activin-A have been implicated in airway remodeling in asthma, but the modulation of their specific signaling pathways after disease activation remains undefined. OBJECTIVE: To define the expression kinetics of TGF-beta(1), activin-A ligands, and follistatin (a natural activin inhibitor), their type I and type II receptors (activin-like kinase[ALK]-1, ALK-5, ALK-4, TbetaRII, and ActRIIA/RIIB) and activation of signaling (via phosphorylated (p) Smad2), in the asthmatic airway after allergen challenge. METHODS: Immunohistochemistry was performed on bronchial biopsies from 15 mild atopic patients with asthma (median age, 25 years; median FEV(1)% predicted, 97%) at baseline and 24 hours after allergen inhalation. Functional effects of activin-A were evaluated by using cultured normal human bronchial epithelial (NHBE) cells. RESULTS: pSmad2(+) epithelial cells increased at 24 hours (P = .03), and pSmad2 was detected in submucosal cells. No modulation of activin-A, follistatin, or TGF-beta(1) expression was demonstrated. Activin receptor(+) cells increased after allergen challenge: ALK-4 in epithelium (P = .04) and submucosa (P = .04), and ActRIIA in epithelium (P = .01). The TGF-beta receptor ALK-5 expression was minimal in the submucosa at baseline and after challenge and was downregulated in the epithelium after challenge (P = .02), whereas ALK-1 and TbetaRII expression in the submucosa increased after allergen challenge (P = .03 and P = .004, respectively). ALK-1 and ALK-4 expression by T cells was increased after allergen challenge. Activin-A induced NHBE cell proliferation, was produced by NHBE cells in response to TNF-alpha, and downregulated TNF-alpha and IL-13-induced chemokine production by NHBE cells. CONCLUSION: Both TGF-beta and activin signaling pathways are activated on allergen provocation in asthma. Activin-A may contribute to resolution of inflammation.

Basal expression of bone morphogenetic protein receptor is reduced in mild asthma.

RATIONALE: Despite increasing recognition of bone morphogenetic protein (BMP) signaling in tissue remodeling, the expression pattern of ligands and signaling pathways remain undefined in the asthmatic airway. OBJECTIVES: To determine expression of BMP ligands (BMP-2, BMP-4, and BMP-7) and type I and type II receptors (ALK-2, ALK-3, ALK-6, and BMPRII) as well as evidence for activation of BMP signaling via detection of phosphorylated Smad1/5 (pSmad1/5) expression in asthmatic airways at baseline (compared with nonasthmatic controls), and after allergen challenge. METHODS: Bronchial biopsies were obtained from 6 nonasthmatic control volunteers, and 15 atopic patients with asthma (median age, 25 yr; median FEV(1)% predicted, 97%) at baseline, then at 24 hours and 7 days after allergen challenge. Expression of BMP ligands, receptors, and signaling was analyzed using immunohistochemistry. MEASUREMENTS AND MAIN RESULTS: BMP ligand expression did not differ between asthmatic and control airways at baseline. Compared with the normal airway, there was significant down-regulation of ALK-2 (P = 0.001), ALK-6 (P = 0.0009), and BMPRII (P = 0.009) expression in asthma. Allergen challenge was associated with marked and sustained up-regulation of BMP-7 in airway epithelium (P = 0.017) and infiltrating inflammatory cells (P = 0.071) (predominantly in eosinophils, but also CD4(+) T cells, mast cells, and macrophages). Up-regulation of pSmad1/5 expression (P = 0.031), ALK-2 (P = 0.002), and ALK-6 (P < 0.001) was observed indicating active signaling. CONCLUSIONS: BMP receptor expression is down-regulated in the asthmatic airway, which may impede repair responses. Allergen provocation increases expression of the regulatory ligand BMP-7, activates BMP signaling, and increases receptor expression, all of which may contribute to repair and control of inflammation.

Was Thomas Wharton Jones FRS, assistant to the infamous Dr Knox, the first to recognise the blood eosinophil?

Thomas Wharton Jones (1808-91), described as a 'genius' by his famous pupil Thomas Henry Huxley, was an Edinburgh medical graduate. At the age of 19 years he was appointed anatomy demonstrator to the infamous Dr Robert Knox so unwittingly becoming caught up in the Burke and Hare scandal. Escaping to Glasgow, and then to Cork and London, Jones eventually became an outstanding physiologist and ophthalmologist. His seminal observations included scholarly treatises on the vasculature in inflammation together with descriptions of the contractile movement of white blood cells, as well as studies on regeneration and repair, astigmatism and retinitis pigmentosa. He was admitted as a Fellow of the Royal Society in 1840. One of his seminal contributions was his detailed description of 'granular cells' in the blood of a large number of animal species, including man. His illustrations suggest strongly these were eosinophils, predating Paul Erhlich's definitive studies (using aniline dyes) by 33 years. In later life he was found destitute in his London home and 'rescued' by friends and colleagues. William Gladstone was persuaded to give Jones a civil list pension. He lived out the rest of his life in Ventnor on the Isle of Wight.

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.

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.

The role of eosinophils in the pathogenesis of asthma.

Two recent papers have addressed the ever-intriguing question of the role of eosinophils in asthma. Both groups used experimental models of airway inflammation in mice that were gene targeted to selectively ablate the eosinophil lineage. One group found that eosinophils were required for both airway hyperresponsiveness and mucus accumulation. The other demonstrated a 'critical role' for the cell in airway remodelling. The results, although largely confirmatory of previous studies both in mice and humans, put the eosinophil firmly back on the asthma stage and strengthen the case for developing effective eosinophil-depleting agents for clinical use.

The role of T lymphocytes in asthma.

There is now overwhelming evidence to support a major role for T cells in asthma, in particular the involvement of T helper type 2 (Th2) cells in atopic allergic asthma as well as nonatopic and occupational asthma. There may also be a minor contribution from T cytotoxic type 2 CD8+T cells. Several Th2 cytokines have potential to modulate airway inflammation, in particular interleukin-13 which induces airway hyperresponsiveness independently of IgE and eosinophilia in animal models. The identification of transcription factors controlling Th1, Th2 and T-regulatory cell (T(Reg)) development further support the Th2 hypothesis since GATA3 is overexpressed and T-bet underexpressed in the asthmatic airway and Foxp3 is induced in asthma by corticosteroid treatment. Specific T-cell-directed immunotherapy may allow induction/modulation of T-cell responses, and elucidation of the mechanisms of T(Regs) may allow further optimization of immunotherapy. Recent advances in the understanding of dendritic cell function in directing T-cell responses may uncover further therapeutic targets. Efficacy of cyclosporin and anti-CD4 treatment in chronic severe asthma argues for continued T-cell involvement, but whether remodeling contributes to pathology inaccessible to antiinflammatory treatment or T-cell immunotherapy remains an important question.

Paul Ehrlich and the Early History of Granulocytes.

Paul Ehrlich's techniques, published between 1879 and 1880, for staining blood films using coal tar dyes, and his method of differential blood cell counting, ended years of speculation regarding the classification of white cells. Acidic and basic dyes had allowed him to recognize eosinophil and basophil granules, respectively, work that was a direct continuation of his discovery of the tissue mast cell described in his doctoral thesis. Ehrlich went on to develop neutral dyes that identified epsilon granules in neutrophils ("cells with polymorphous nuclei"). He also speculated, for the most part correctly, on the formation, function, and fate of blood neutrophils and eosinophils. Before Ehrlich, a number of important observations had been made on white cells and their role in health and disease. Among the most notable were William Hewson's studies of blood and lymph; the early descriptions of leukemia by Alfred Donné, John Hughes Bennett, Rudolf Virchow, and others; as well as seminal observations on inflammation by William Addison, Friedrich von Recklinghausen, and Julius Cohnheim. Eosinophils were almost certainly recognized previously by others. In 1846, Thomas Wharton Jones (1808-1891) described "granule blood-cells" in several species including humans. The term "granule cell" had also been used by Julius Vogel (1814-1880), who had previously observed similar cells in inflammatory exudates. Vogel, in turn, was aware of the work of Gottlieb Gluge (1812-1898), who had observed "compound inflammatory globules" in pus and serum that resembled eosinophils. Almost 20 years before Ehrlich developed his staining methods, Max Johann Schultze (1825-1874) performed functional experiments on fine and coarse granular cells using a warm stage microscopic technique and showed they had amoeboid movement and phagocytic abilities. Despite these earlier observations, it was Ehrlich's use of stains that heralded the modern era of studies of leukocyte biology and pathology.

T cell epitope immunotherapy induces a CD4+ T cell population with regulatory activity.

BACKGROUND: Synthetic peptides, representing CD4(+) T cell epitopes, derived from the primary sequence of allergen molecules have been used to down-regulate allergic inflammation in sensitised individuals. Treatment of allergic diseases with peptides may offer substantial advantages over treatment with native allergen molecules because of the reduced potential for cross-linking IgE bound to the surface of mast cells and basophils. METHODS AND FINDINGS: In this study we address the mechanism of action of peptide immunotherapy (PIT) in cat-allergic, asthmatic patients. Cell-division-tracking dyes, cell-mixing experiments, surface phenotyping, and cytokine measurements were used to investigate immunomodulation in peripheral blood mononuclear cells (PBMCs) after therapy. Proliferative responses of PBMCs to allergen extract were significantly reduced after PIT. This was associated with modified cytokine profiles generally characterised by an increase in interleukin-10 and a decrease in interleukin-5 production. CD4(+) cells isolated after PIT were able to actively suppress allergen-specific proliferative responses of pretreatment CD4(neg) PBMCs in co-culture experiments. PIT was associated with a significant increase in surface expression of CD5 on both CD4(+) and CD8(+) PBMCs. CONCLUSION: This study provides evidence for the induction of a population of CD4(+) T cells with suppressor/regulatory activity following PIT. Furthermore, up-regulation of cell surface levels of CD5 may contribute to reduced reactivity to allergen.

Immunomodulation in asthma: mechanisms and possible pitfalls.

Atopic diseases, including atopic asthma, are characterized by T helper cell (Th)2 cytokine pathology. The increased prevalence of asthma and allergic diseases, as well as Th1-associated conditions, is linked to 'excessive' hygiene. Several new immunomodulatory strategies in asthma and allergy, such as peptide therapy and DNA vaccines, show promise and are under clinical evaluation. They appear to exert their effects by producing a Th2 to Th1 shift, as well as inducing regulatory cytokines such as interleukin-10 and transforming growth factor-beta. There is no evidence that such approaches are associated with Th1 pathology in humans, although lung inflammation induced by Th1 cells has been observed in mice. IL-10 plays a key regulatory role in dampening both Th2- and Th1-associated diseases. Failure to stimulate regulatory responses could explain the rising trends in allergy and autoimmunity, and also partly explain the mode of action of allergen-injection immunotherapy and new immunomodulatory approaches.

Peptide-based vaccines in the treatment of specific allergy.

The efficacy of conventional allergen-specific immunotherapy (SIT) for allergic conditions and venom hypersensitivity is well documented. However it's use is limited due allergic side effects including anaphylaxis and the difficulty of standardising proteins in complex allergenic mixtures. The aim of new therapeutic strategies is to circumvent these limitations and approaches include allergen non-specific therapy, such as anti-IgE and anti-cytokine therapy and other allergen specific techniques including the peptide based vaccines (PBV), modified allergens (allergoids) and DNA vaccines. PBV are small linear peptide fragments containing T cell epitopes which are designed to reduce the ability to cross link antigen-specific IgE. Studies in animal models have confirmed proof of principle demonstrating the induction of hyporesponsiveness using high doses of peptides. However, the principle limitation to clinical use of PBV is the polymorphism of HLA class II molecules. There are ongoing clinical studies using peptide-based vaccines for cat, bee and grass allergies--looking at both immunological mechanisms and clinical outcome measures. The mechanisms underlying the efficacy of PBV appear to be similar to those described for classical immunological tolerance. Thus, the peptides may induce anergy due to absence of co-stimulation, activation-induced cell death, a switch from a Th2 to a Th1 cytokine profile, the induction of regulatory T cells or combinations of these mechanisms. Successful immunotherapy, in bee sensitive individuals, is associated with the elaboration of IL-10. Clonal deletion is unlikely as an overall mechanism as there is evidence that the subsequent in vitro response to associated, non-injected, peptides can be suppressed. Mechanistic studies continue to provide insight into the mode of action of whole allergen and peptide-based immunotherapy. Clinical studies designed on the basis of these observations hold the promise of safer vaccines with improved efficacy. Whether this strategy can be used for allergy to complex allergen mixtures such as dust mites will need further evaluation.

Anti-interleukin-5 therapy for asthma and hypereosinophilic syndrome.

Interleukin 5 (IL-5) is a key cytokine in the regulation of eosinophilia and eosinophil activation in humans. Monoclonal antibodies to anti-IL-5 have become available for use in clinical studies in humans. This article discusses the rationale for the use of anti-IL-5 therapy in asthma and hypereosinophilic syndrome and summarizes the available clinical data on the use of anti-IL-5 to treat these disorders.