Technical standards in allergen exposure chambers worldwide - an EAACI Task Force Report.

Allergen exposure chambers (AECs) can be used for controlled exposure to allergenic and non-allergenic airborne particles in an enclosed environment, in order to (i) characterize the pathological features of respiratory diseases and (ii) contribute to and accelerate the clinical development of pharmacological treatments and allergen immunotherapy for allergic disease of the respiratory tract (such as allergic rhinitis, allergic rhinoconjunctivitis, and allergic asthma). In the guidelines of the European Medicines Agency for the clinical development of products for allergen immunotherapy (AIT), the role of AECs in determining primary endpoints in dose-finding Phase II trials is emphasized. Although methodologically insulated from the variability of natural pollen exposure, chamber models remain confined to supporting secondary, rather than primary, endpoints in Phase III registration trials. The need for further validation in comparison with field exposure is clearly mandated. On this basis, the European Academy of Allergy and Clinical Immunology (EAACI) initiated a Task Force in 2015 charged to gain a better understanding of how AECs can generate knowledge about respiratory allergies and can contribute to the clinical development of treatments. Researchers working with AECs worldwide were asked to provide technical information in eight sections: (i) dimensions and structure of the AEC, (ii) AEC staff, (iii) airflow, air processing, and operating conditions, (iv) particle dispersal, (v) pollen/particle counting, (vi) safety and non-contamination measures, (vii) procedures for symptom assessments, (viii) tested allergens/substances and validation procedures. On this basis, a minimal set of technical requirements for AECs applied to the field of allergology is proposed.

The Effect of a Thixotropic Nasal Gel on Nasal Symptoms and Inflammatory Biomarkers in Seasonal Allergic Rhinitis.

BACKGROUND: Drug-free viscous nasal applications have been shown to reduce nasal symptoms in individuals with seasonal allergic rhinitis (SAR). Nascum®-Plus (NP), a commercially available thixotropic gel, has been designed to reduce dryness and soreness of the nasal mucosa and prevent the absorption of small particles. OBJECTIVES: The aim of this study was to assess the efficacy of single-dose NP in treating nasal symptoms and secretion during challenge in an allergen challenge chamber (ACC). Furthermore, the effect of this treatment on biomarkers and immune cells of the allergic cascade were measured. METHODS: This open-label, cross-over, sequence-randomized, monocentric trial randomized 18 adults with SAR and a positive skin prick test reaction to Dactylis glomerata pollen to receive NP or no treatment during two 4-h ACC sessions 3 weeks apart. On Day 1, 9 subjects were challenged for 4 h with treatment, the other 9 without treatment, and vice versa on Day 22. Nasal lavage fluid and nasal filter eluate samples were obtained pre, 2, and 18 h post challenge in the ACC. RESULTS: NP significantly reduced nasal symptoms, assessed by total nasal symptom score (p < 0.001), and minimized nasal secretion (p = 0.047), while no significant effect on biomarkers and immune cells in the nasal fluid was observed. The treatment was safe and well-tolerated. CONCLUSIONS: The physical barrier built by NP nasal gel can be safely applied in patients with allergic rhinitis. It reduces allergic nasal symptoms and secretion, but application of a single dose does not affect local inflammatory biomarkers.

International Consensus Statement on Allergy and Rhinology: Allergic Rhinitis.

BACKGROUND: Critical examination of the quality and validity of available allergic rhinitis (AR) literature is necessary to improve understanding and to appropriately translate this knowledge to clinical care of the AR patient. To evaluate the existing AR literature, international multidisciplinary experts with an interest in AR have produced the International Consensus statement on Allergy and Rhinology: Allergic Rhinitis (ICAR:AR). METHODS: Using previously described methodology, specific topics were developed relating to AR. Each topic was assigned a literature review, evidence-based review (EBR), or evidence-based review with recommendations (EBRR) format as dictated by available evidence and purpose within the ICAR:AR document. Following iterative reviews of each topic, the ICAR:AR document was synthesized and reviewed by all authors for consensus. RESULTS: The ICAR:AR document addresses over 100 individual topics related to AR, including diagnosis, pathophysiology, epidemiology, disease burden, risk factors for the development of AR, allergy testing modalities, treatment, and other conditions/comorbidities associated with AR. CONCLUSION: This critical review of the AR literature has identified several strengths; providers can be confident that treatment decisions are supported by rigorous studies. However, there are also substantial gaps in the AR literature. These knowledge gaps should be viewed as opportunities for improvement, as often the things that we teach and the medicine that we practice are not based on the best quality evidence. This document aims to highlight the strengths and weaknesses of the AR literature to identify areas for future AR research and improved understanding.

Specificity and reproducibility of nasal biomarkers in patients with allergic rhinitis after allergen challenge chamber exposure.

BACKGROUND: Allergic rhinitis is an inflammatory disease that causes cellular influx and mediator release in the nose. These inflammatory changes might be used as nasal biomarkers to assess the efficacy of novel anti-allergic treatments. OBJECTIVE: To assess the specificity and reproducibility of nasal biomarkers in patients with allergic rhinitis after grass pollen exposure in an allergen challenge chamber. METHODS: In a monocenter pilot study, 15 patients with allergic rhinitis and 19 healthy individuals underwent two 4-hour Dactylis glomerate pollen challenges in the challenge chamber with an interval of 21 days. Before challenge, on exit, and after 2 and 22 hours, a nasal lavage was performed and nasal secretions were collected on filter paper to determine a wide panel of cells and mediators. Furthermore, total nasal symptom score, nasal flow, and nasal nitric oxide were measured. RESULTS: Pollen exposure significantly increased eosinophil, interleukin (IL) 5, IL-6, IL-13, and macrophage inflammatory protein 1ß levels in allergic patients but not in healthy individuals. The effect could be reproduced for eosinophils, IL-5, IL-6, and macrophage inflammatory protein 1ß after the second allergen challenge. By contrast, the IL-13 levels were higher and eotaxin levels first increased after repetitive allergen challenge. There was no correlation between total nasal symptom score and elevated cell or cytokine levels. Nasal nitric oxide levels were nonspecifically elevated in both patients with allergy and healthy controls. CONCLUSION: A subset of cellular and soluble biomarkers in nasal lavage and secretion reveals specificity and reproducibility in patients with allergic rhinitis. These can be used to measure the immunologic efficacy of antiallergic treatments in an allergen challenge chamber. Carryover effects attributable to priming must be considered when designing cross-over studies. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT00297843.

Efficacy and safety of a novel nasal steroid, S0597, in patients with seasonal allergic rhinitis.

BACKGROUND: Allergic rhinitis (AR) poses a significant global burden with increasing prevalence. Although intranasal glucocorticosteroids are effective, older agents can have limiting side effects. S0597, a novel intranasal glucocorticosteroid, has demonstrated good safety and tolerability during preclinical and phase 1 studies. OBJECTIVE: To assess the clinical efficacy, safety, and tolerability of different doses of S0597 nasal spray vs placebo in patients with seasonal AR. METHODS: This phase 2, randomized, double-blinded, placebo-controlled, parallel-group, single-center study randomized 159 patients 18 to 65 years old (mean age 37.8 years) with a positive skin prick test reaction for Dactylis glomerata to receive S0597 at 200, 400, or 800 µg/d or placebo for 15 days. On days 1 (baseline), 15, and 16, patients underwent a 4-hour pollen challenge to evaluate treatment efficacy measured by the change in total nasal symptom score (TNSS) from baseline to days 15 and 16 and changes in TNSS subscales and nasal secretion. RESULTS: Statistically significant improvements in TNSS from baseline to days 15 and 16 were observed with all S0597 doses vs placebo (P = .0005 overall), with the greatest improvements observed in the highest-dose group (P < .0001). Significant decreases were observed in each S0597 dose group vs placebo for TNSS subscales and nasal secretion. Improvements in nasal secretion were related to dose, with the greatest decreases from baseline in the 800-µg/d group on days 15 and 16 (P < .0001). CONCLUSION: Treatment with S0597 at 200, 400, and 800 µg/d by 2 divided doses for 2 weeks was safe and significantly more effective than placebo for improving nasal symptoms associated with grass pollen-induced seasonal AR in adults. TRIAL REGISTRATION: ClinicalTrials.gov, identifier NCT01614691.

Exacerbation of atopic dermatitis on grass pollen exposure in an environmental challenge chamber.

BACKGROUND: It has frequently been speculated that pruritus and skin lesions develop after topical exposure to aeroallergens in sensitized patients with atopic dermatitis (AD). OBJECTIVE: We sought to study cutaneous reactions to grass pollen in adult patients with AD with accompanying clear IgE sensitization to grass allergen in an environmental challenge chamber using a monocenter, double-blind, placebo-controlled study design. METHODS: Subjects were challenged on 2 consecutive days with either 4000 pollen grains/m(3) of Dactylis glomerata pollen or clean air. The severity of AD was assessed at each study visit up to 5 days after challenge by (objective) scoring of AD (SCORAD). Additionally, air-exposed and non-air-exposed skin areas were each scored using local SCORAD scoring and investigator global assessments. Levels of a series of serum cytokines and chemokines were determined by using a Luminex-based immunoassay. The primary end point of the study was the change in objective SCORAD scores between prechallenge and postchallenge values. RESULTS: Exposure to grass pollen induced a significant worsening of AD. A pronounced eczema flare-up of air-exposed rather than covered skin areas occurred. In grass pollen-exposed subjects a significantly higher increase in CCL17, CCL22, and IL-4 serum levels was observed. CONCLUSIONS: This study demonstrates that controlled exposure to airborne allergens of patients with a so-called extrinsic IgE-mediated form of AD induced a worsening of cutaneous symptoms.

Efficacy of the oral chemoattractant receptor homologous molecule on TH2 cells antagonist BI 671800 in patients with seasonal allergic rhinitis.

BACKGROUND: The inflammatory response in patients with seasonal allergic rhinitis (SAR) is partly mediated by the prostaglandin D2 receptor chemoattractant receptor homologous molecule on T(H)2 cells (CRTH2). OBJECTIVE: We sought to investigate the efficacy and safety of the oral CRTH2 antagonist BI 671800 (50, 200, and 400 mg twice daily), fluticasone propionate nasal spray (200 µg once daily), or oral montelukast (10 mg once daily) administered for 2 weeks in patients with SAR. METHODS: In this randomized, double-blind, placebo-controlled, partial-crossover study, participants aged 18 to 65 years with a positive skin prick test to Dactylis glomerata pollen were exposed to out-of-season allergen in the environmental challenge chamber for 6 hours. The primary efficacy variable was the total nasal symptom score assessed as the area under the curve (AUC)(0-6h). RESULTS: In total, 146 patients (63.7% male; mean age, 36.1 years) were randomized. The adjusted mean total nasal symptom score AUC(0-6h) was significantly reduced versus placebo with 200 mg of BI 671800 (absolute difference, -0.85; percentage difference, -17%; P = .0026), montelukast (absolute difference, -0.74; percentage difference, -15%; P = .0115), and fluticasone propionate (absolute difference, -1.64; percentage difference, -33%; P < .0001). Compared with placebo, BI 671800 significantly reduced nasal eosinophil values (P < .05 for all doses), significantly inhibited nasal inflammatory cytokine levels (IL-4 and eotaxin, P < .05; 200 mg twice daily), and induced a dose-related reduction in ex vivo prostaglandin D2-mediated eosinophil shape change. CONCLUSION: Two hundred milligrams of BI 671800 twice daily demonstrated efficacy in treating SAR symptoms induced by environmental challenge chamber allergen exposure and had a favorable safety profile.

LPS-induced lung inflammation in marmoset monkeys - an acute model for anti-inflammatory drug testing.

Increasing incidence and substantial morbidity and mortality of respiratory diseases requires the development of new human-specific anti-inflammatory and disease-modifying therapeutics. Therefore, new predictive animal models that closely reflect human lung pathology are needed. In the current study, a tiered acute lipopolysaccharide (LPS)-induced inflammation model was established in marmoset monkeys (Callithrix jacchus) to reflect crucial features of inflammatory lung diseases. Firstly, in an ex vivo approach marmoset and, for the purposes of comparison, human precision-cut lung slices (PCLS) were stimulated with LPS in the presence or absence of the phosphodiesterase-4 (PDE4) inhibitor roflumilast. Pro-inflammatory cytokines including tumor necrosis factor-alpha (TNF-α) and macrophage inflammatory protein-1 beta (MIP-1ß) were measured. The corticosteroid dexamethasone was used as treatment control. Secondly, in an in vivo approach marmosets were pre-treated with roflumilast or dexamethasone and unilaterally challenged with LPS. Ipsilateral bronchoalveolar lavage (BAL) was conducted 18 hours after LPS challenge. BAL fluid was processed and analyzed for neutrophils, TNF-α, and MIP-1ß. TNF-α release in marmoset PCLS correlated significantly with human PCLS. Roflumilast treatment significantly reduced TNF-α secretion ex vivo in both species, with comparable half maximal inhibitory concentration (IC(50)). LPS instillation into marmoset lungs caused a profound inflammation as shown by neutrophilic influx and increased TNF-α and MIP-1ß levels in BAL fluid. This inflammatory response was significantly suppressed by roflumilast and dexamethasone. The close similarity of marmoset and human lungs regarding LPS-induced inflammation and the significant anti-inflammatory effect of approved pharmaceuticals assess the suitability of marmoset monkeys to serve as a promising model for studying anti-inflammatory drugs.

Pollen starch granules in bronchial inflammation.

BACKGROUND: Pollen grains with a diameter of more than 10 µm preferentially deposit in the upper airways. Their contribution to lower airway inflammation is unclear. One hypothesis is that lower airway inflammation is mainly caused by allergen containing pollen starch granules, which are released from the pollen grains and can easily enter the peripheral airways because of their smaller size. OBJECTIVE: To investigate the differential effect of pollen grains and pollen starch granules on nasal symptoms and lower airway inflammation. METHODS: In a 2-period crossover design, 30 patients with allergic rhinitis and mild intermittent asthma underwent 2 allergen challenges on consecutive days in an environmental challenge chamber with either a mixture of pollen grains plus starch granules or starch granules only. End points were the total nasal symptom score (TNSS), nasal secretion weight, nasal flow, spirometry, and exhaled nitric oxide (eNO). RESULTS: The presence of pollen grains had a significant and considerable effect on increase in TNSS and secretion weight and on decrease in nasal flow. Starch granules alone only had minimal effects on nasal symptoms. Challenges with starch granules significantly increased eNO. Pollen had no effect on eNO. CONCLUSION: Pollen grains cause nasal symptoms but do not augment lower airway inflammation, whereas starch granules trigger lower airway inflammation but hardly induce nasal symptoms.

Surfactant Protein D modulates allergen particle uptake and inflammatory response in a human epithelial airway model.

BACKGROUND: Allergen-containing subpollen particles (SPP) are released from whole plant pollen upon contact with water or even high humidity. Because of their size SPP can preferentially reach the lower airways where they come into contact with surfactant protein (SP)-D. The aim of the present study was to investigate the influence of SP-D in a complex three-dimensional human epithelial airway model, which simulates the most important barrier functions of the epithelial airway. The uptake of SPP as well as the secretion of pro-inflammatory cytokines was investigated. METHODS: SPP were isolated from timothy grass and subsequently fluorescently labeled. A human epithelial airway model was built by using human Type II-pneumocyte like cells (A549 cells), human monocyte derived macrophages as well as human monocyte derived dendritic cells. The epithelial cell model was incubated with SPP in the presence and absence of surfactant protein D. Particle uptake was evaluated by confocal microscopy and advanced computer-controlled analysis. Finally, human primary CD4+ T-Cells were added to the epithelial airway model and soluble mediators were measured by enzyme linked immunosorbent assay or bead array. RESULTS: SPP were taken up by epithelial cells, macrophages, and dendritic cells. This uptake coincided with secretion of pro-inflammatory cytokines and chemokines. SP-D modulated the uptake of SPP in a cell type specific way (e.g. increased number of macrophages and epithelial cells, which participated in allergen particle uptake) and led to a decreased secretion of pro-inflammatory cytokines. CONCLUSION: These results display a possible mechanism of how SP-D can modulate the inflammatory response to inhaled allergen.

Anti-allergic drug testing in an environmental challenge chamber is suitable both in and out of the relevant pollen season.

BACKGROUND: An environmental challenge chamber (ECC) is a useful tool to expose allergic patients to relevant allergens in a controlled indoor setting and to test anti-allergic treatment. Hitherto, ECC studies with grass pollen are conducted primarily outside of the pollen season to avoid the influence of natural pollen exposure. OBJECTIVE: To investigate whether an established anti-allergic treatment, a combination of cetirizine (CET) and pseudoephedrine (PSE), shows an equivalent treatment effect within and outside of the grass pollen season when tested in an ECC. METHODS: In a randomized, placebo-controlled, double-blind, four-way crossover study, the effect of a combination of 10 mg CET and 120 mg PSE compared with placebo on nasal symptoms, nasal flow, and nasal secretion was investigated in 70 patients with seasonal allergic rhinitis. Subjects underwent four 6-hour pollen challenges in an ECC with administration of the drugs after 2 hours. Two challenges were conducted within the grass pollen season and two out of the grass pollen season. RESULTS: The active treatment significantly improved nasal symptoms and nasal flow and significantly reduced the amount of nasal secretion compared with placebo both within and outside of the pollen season (P < .0001 each). The treatment effect was not different between the seasons (P > .05). CONCLUSION: Controlled allergen provocation in an ECC can be used to test anti-allergic treatment both within and outside of the grass pollen season.

Surfactant protein D modulates pulmonary clearance of pollen starch granules.

Pollen starch granules (PSGs) are allergen particles that get into contact with pulmonary surfactant and phagocytes in the terminal airways. In this study, the effects of surfactant protein D (SP-D) on the interaction of PSGs with phagocytes and on the pulmonary clearance of PSGs were determined. Fluorescently labeled PSGs were incubated in vitro with murine lung macrophages or dendritic cells (DCs) ± recombinant rat SP-D (rrSP-D). In addition, the effect of SP-D on uptake of PSGs by lung macrophages and DCs was studied in vivo. Furthermore, PSGs were instilled in Balb/c mice and the effects of SP-D on total lung clearance were assessed by optical imaging. SP-D treatment increased the number of PSG-positive macrophages and DCs in vitro. Furthermore, SP-D accelerated uptake/binding by alveolar macrophages and reduced the number of PSG-positive tissue macrophages and DCs at 24 hours. However, SP-D did not affect total lung clearance of PSGs and it did not enhance the T-cell proliferation induced by PSG-positive DCs. In conclusion, SP-D increased PSG-positive cells in vitro and accelerated PSG binding/uptake in vivo. The observed effects were limited to cellular clearance mechanisms and did not affect the total clearance of PSGs from the lung.

Allergen particle binding by human primary bronchial epithelial cells is modulated by surfactant protein D.

BACKGROUND: Allergen-containing subpollen particles (SPP) are released from whole plant pollen upon contact with water or even high humidity. Because of their size SPP can preferentially reach the lower airways where they come into contact with surfactant protein (SP)-D. Our previous work demonstrated that SP-D increases the uptake of SPP by alveolar macrophages. In the present study, we investigated the uptake of SPP in human primary epithelial cells and the potential modulation by SP-D. The patho-physiological consequence was evaluated by measurement of pro-inflammatory mediators. METHODS: SPP were isolated from timothy grass and subsequently fluorescently labelled. Human primary bronchial epithelial cells were incubated with SPP or polystyrene particles (PP) in the presence and absence of surfactant protein D. In addition, different sizes and surface charges of the PP were studied. Particle uptake was evaluated by flow cytometry and confocal microscopy. Soluble mediators were measured by enzyme linked immunosorbent assay or bead array. RESULTS: SPP were taken up by primary epithelial cells in a dose dependent manner. This uptake was coincided with secretion of Interleukin (IL)-8. SP-D increased the fraction of bronchial epithelial cells that bound SPP but not the fraction of cells that internalized SPP. SPP-induced secretion of IL-8 was further increased by SP-D. PP were bound and internalized by epithelial cells but this was not modulated by SP-D. CONCLUSIONS: Epithelial cells bind and internalize SPP and PP which leads to increased IL-8 secretion. SP-D promotes attachment of SPP to epithelial cells and may thus be involved in the inflammatory response to inhaled allergen.

Glutathione improves the function of porcine pulmonary grafts stored for twenty-four hours in low-potassium dextran solution.

BACKGROUND: Flush perfusion with low-potassium dextran is the standard strategy in clinical lung preservation. Despite improved outcome, endothelial cell injury and surfactant dysfunction remain a significant problem after lung transplantation. The radical scavenger glutathione has been shown to be responsible for the efficacy of Celsior solution in lung preservation. We tested the hypothesis that the addition of glutathione to low-potassium dextran might further improve graft function by ameliorating ischemia-reperfusion injury. METHODS: In 12 domestic pigs, lungs were flush preserved with either low-potassium dextran (n = 6) or low-potassium dextran supplemented by 5 mmol glutathione (n = 6). Left single lung transplantation was performed after 24-hour storage in low-potassium dextran at 8 degrees C. After 15 minutes of reperfusion the right main bronchus and pulmonary artery were crossclamped. Hemodynamic and respiratory measures were recorded in 30-minute intervals for a total observation period of 7 hours. Bronchoalveolar lavage fluid was obtained from the native lung and 2 hours after reperfusion from the graft. Bronchoalveolar lavage fluid and surfactant composition, and surfactant function analyses were performed. Neutrophil sequestration was assessed by myeloperoxidase activity assay. Tissue water content was calculated from wet/dry weight ratios at the end of the experiment. RESULTS: In the low-potassium dextran group, 2 animals died during reperfusion. After reperfusion, pulmonary vascular resistance (P = .01) and pulmonary artery pressure remained lower in the glutathione/low-potassium dextran group, which was associated with a higher cardiac output (P = .05) in this group. Also, the oxygenation index at the end of the observation period was higher in the glutathione/low-potassium dextran group compared with the low-potassium dextran group (430 +/- 130 vs 338 +/- 184, respectively; P < .05). The graft water content representing postreperfusion lung edema was not different between the 2 study groups. Alteration of surfactant was less in the glutathione/low-potassium dextran group with a significantly decreased small to large aggregate ratio (P = .03) versus low-potassium dextran group. Myeloperoxidase activity was twice as high in the low-potassium dextran group when compared with the glutathione/low-potassium dextran group (glutathione/low-potassium dextran: 134 +/- 110 mU/g vs low-potassium dextran: 274 +/- 168 mU/g, P = .07). CONCLUSION: The addition of glutathione to low-potassium dextran preservation solution reveals beneficial effects on vascular function and surfactant composition in transplanted lungs. Therefore, glutathione ameliorates ischemia-reperfusion injury in a preclinical model of lung transplantation. Future studies are needed to evaluate this promising modification in clinical lung transplantation.

Surfactant protein D decreases pollen-induced IgE-dependent mast cell degranulation.

Mast cells play a key role in allergy and asthma. They reside at the host-environment interface and are among the first cells to make contact with inhaled microorganisms and particulate antigens. Pulmonary surfactant proteins A and D (SP-A and SP-D) function in lung host defense by enhancing microbe phagocytosis and mediating other immune cell functions, but little is known about their effects on mast cells. We hypothesized that SP-A and/or SP-D modulate IgE-dependent mast cell functions. Pollen starch granules (PSG) extracted from Dactylis glomerata and coated with trinitrophenol (TNP) were used as a model of an inhaled organic particulate allergen. Our data revealed that SP-D inhibited by 50% the release of beta-hexosaminidase by peritoneal mast cells sensitized with IgE anti-TNP and stimulated with TNP-PSG. In contrast, SP-A had no effect. Furthermore, SP-D aggregated PSG in a dose-dependent manner, and this aggregation was mediated by SP-D's carbohydrate recognition domain. A single arm SP-D mutant (RrSP-Dser15,20) neither aggregated PSG nor inhibited degranulation, suggesting that multimerization of SP-D is required for maximal PSG aggregation and inhibition of PSG-induced mast cell degranulation. This study is the first to demonstrate that SP-D modulates IgE-mediated mast cell functions, which are important in asthma and allergic inflammation.

Surfactant protein D increases phagocytosis and aggregation of pollen-allergen starch granules.

Recent studies have shown that surfactant components, in particular the collectins surfactant protein (SP)-A and -D, modulate the phagocytosis of various pathogens by alveolar macrophages. This interaction might be important not only for the elimination of pathogens but also for the elimination of inhaled allergens and might explain anti-inflammatory effects of SP-A and SP-D in allergic airway inflammation. We investigated the effect of surfactant components on the phagocytosis of allergen-containing pollen starch granules (PSG) by alveolar macrophages. PSG were isolated from Dactylis glomerata or Phleum pratense, two common grass pollen allergens, and incubated with either rat or human alveolar macrophages in the presence of recombinant human SP-A, SP-A purified from patients suffering from alveolar proteinosis, a recombinant fragment of human SP-D, dodecameric recombinant rat SP-D, or the commercially available surfactant preparations Curosurf and Alveofact. Dodecameric rat recombinant SP-D enhanced binding and phagocytosis of the PSG by alveolar macrophages, whereas the recombinant fragment of human SP-D, SP-A, or the surfactant lipid preparations had no effect. In addition, recombinant rat SP-D bound to the surface of the PSG and induced aggregation. Binding, aggregation, and enhancement of phagocytosis by recombinant rat SP-D was completely blocked by EDTA and inhibited by d-maltose and to a lesser extent by d-galactose, indicating the involvement of the carbohydrate recognition domain of SP-D in these functions. The modulation of allergen phagocytosis by SP-D might play an important role in allergen clearance from the lung and thereby modulate the allergic inflammation of asthma.