Piet L.B. Bruijnzeel

Upregulation of formyl-peptide and interleukin-8—induced eosinophil chemotaxis in patients with allergic asthma

BACKGROUND The cytokine granulocyte-macrophage colony-stimulating factors, interleukin-3 and interleukin-5, are important modulators of eosinophilia and eosinophil function. In particular, eosinophil chemotaxis is very sensitive to cytokine priming. METHODS We evaluated chemotactic responses of eosinophils from patients with allergic asthma. These cells exhibited a primed phenotype as deduced from enhanced responses toward formyl-methionyl-leucyl-phenylalanine and platelet-activating factor and a decreased responsiveness toward granulocyte-macrophage colony-stimulating factor. Bronchoprovocation of patients with allergic asthma with allergen was performed as a possible means to enhance in vivo priming. RESULTS Indeed, eosinophils isolated 3 hours after allergen challenge exhibited a more pronounced primed phenotype, which was reflected by an induction of responsiveness towards interleukin-8. Eosinophil responses induced by platelet-activating factor, formyl-methionyl-leucyl-phenylalanine, complement fragment C5a, interleukin-3, interleukin-5, and granulocyte-macrophage colony-stimulating factor were not significantly altered after allergen challenge. CONCLUSION These data provide further evidence that eosinophils are already primed in the peripheral blood of individuals with allergic asthma. This is most likely due to the presence of circulating cytokines in the peripheral blood of those individuals. This in vivo priming results in selective upregulation and downregulation of responses toward various chemotaxins, which may be released in the lungs during allergic inflammation.

Evaluation of variables influencing the outcome of the atopy patch test

BACKGROUND The number of positive atopy patch test (APT) results in patients with atopic eczema (AE) varies in different studies, probably because of different test techniques. Variables that may influence the outcome of the APT were evaluated. METHODS APTs were performed in 84 patients with AE, 30 control patients with atopic disease, and 85 healthy volunteers, with house dust mite and grass pollen allergens in concentrations of 100, 1000, 10,000, and 100,000 allergenic units/ml. The influence of 0, 10, or 20 tape strippings was investigated. The tests were performed on the back and/or the antecubital fossa and evaluated after 20 minutes and 24, 48, and 72 hours. In all patients the total and specific serum IgE levels were measured. RESULTS The maximal number of positive APT results were obtained under the following conditions: an allergen concentration equal to 10,000 allergenic units/ml, 10 tape strippings and readings at 24 and 48 hours. Positive APT results were observed in five of 30 control patients with atopic disease and in none of 85 healthy volunteers. Statistically significantly higher total and allergen-specific serum IgE levels were found in the group of patients with AE with positive APT results. CONCLUSIONS We recommend the previously described conditions to get an optimal method for APT. The correlation between the APT and the total and specific serum IgE suggests an important role for IgE in the reaction mechanism behind the APT.

Evaluation of the atopy patch test and the cutaneous late-phase reaction as relevant models for the study of allergic inflammation in patients with atopic eczema.

OBJECTIVE The study was designed to evaluate the atopy patch test (APT) and the late-phase reaction (LPR) after intracutaneous allergen injection as models for the study of allergic inflammation in atopic eczema. METHODS Immunocytochemistry was used to analyze skin biopsy specimens from sites of APTs and LPRs at 2 and 24 hours and to compare these with lesional and nonlesional skin of patients with atopic eczema. RESULTS A lack of neutrophil infiltration in specimens from both the APT and lesional skin sites was observed, whereas neutrophils were abundantly present in the specimens from LPR sites. With double-staining techniques it was demonstrated that the few neutrophils present in specimens from APT sites and in lesional skin were mostly located in intravascular areas, whereas in the LPR specimens they were located predominantly in extravascular areas. Eosinophils infiltrated at an earlier time point in the LPR as compared with the APT. Furthermore, there was a decrease of intact mast cells in the LPR site compared with the APT sites and lesional skin. No significant difference in T-cell number was observed between the two tests. Upregulation of E-selectin expression on endothelial cells occurred at an earlier time point in the LPR as compared with the APT. CONCLUSION There are important differences in cellular infiltrate between the APT and the LPR. The close macroscopic and microscopic similarities between the specimens from APT sites and lesional skin of patients with atopic eczema support the argument that the APT is a more valid in vivo model with which to study allergic inflammation in atopic eczema than the LPR.

The Pathogenesis of Photoaging: The Role of Neutrophils and Neutrophil-Derived Enzymes

The hallmark of photoaged skin is solar elastosis, which is probably an end product of elastic fiber degradation. Exposure of human skin to a certain threshold of UV, infrared radiation (IR), and heat leads to an influx of neutrophils. These neutrophils are packed with potent proteolytic enzymes capable of degrading collagen and, particularly, elastic fibers. Neutrophil-derived proteolytic enzymes are held responsible for the extracellular matrix (ECM) damage observed in several non-dermatological conditions. Furthermore, neutrophil elastase, a major product of neutrophils, is strongly associated with solar elastosis in mice. Taken together with our data that show in vivo proteolytic activity of neutrophil-derived elastase and matrix metalloproteinases (MMPs) in UV-exposed skin, we have hypothesized earlier that neutrophils are major contributors to the photoaging process. Although several groups have shown that MMPs are also induced in skin exposed to relatively low doses of UV, IR, and heat, clinical data indicate that high(er) doses of UV, IR, and heat are necessary to induce photoaging or photoaging-like pathology in the skin. Therefore, we propose that MMPs generated by suberythemogenic doses of UV and low doses of IR/heat are involved in cellular processes other than ECM degradation.Journal of Investigative Dermatology Symposium Proceedings (2009) 14, 67-72; doi:10.1038/jidsymp.2009.15.

Targeting neutrophilic inflammation in severe neutrophilic asthma: can we target the disease-relevant neutrophil phenotype?

In severe, neutrophilic asthma, neutrophils are thought to have an important role in both the maintenance of the disease and during exacerbations. These patients often display excessive, mucosal airway inflammation with unresolving neutrophilia. Because this variant of asthma is poorly controlled by glucocorticoids, specific pharmacologic targeting of neutrophils seems a plausible therapeutic approach. However, most attempts with this approach have failed in the clinic. We propose that this could be attributed, in part, to an incomplete understanding of the emerging new insights underlying neutrophil homeostasis and life span, neutrophil reverse transmigration, neutrophil phenotypes, and neutrophil transdifferentiation in human health and disease. Of clinical relevance, recent translational studies have started to uncover distinct neutrophil subsets in humans, namely mature and hypersegmented phenotypes that have bimodal immunomodulatory functions during an acute inflammatory response. In this review, we will elaborate on some of the novel insights in neutrophil biology and attempt to translate them into potential consequences for pharmacologic intervention of severe neutrophilic asthma. We speculate that the disease‐relevant neutrophil phenotype should be targeted selectively without compromising the immunomodulatory functions essential for homeostasis and pulmonary immunity. However, the identity and exact functional role of distinct neutrophil phenotypes in inflammatory diseases of the human airway remain elusive.