Altered Skin Prick Test Reactivity and Histamine Release with Extracts from Pollen Exposed to Pollutants

Allergy Pollen Pollutants Histamine Prick test Correspondence to: Dr. Peter Thomas, Dermatologische Klinik und Poliklinik, Ludwig-Maximilians-Universität München, Frauenlobstrasse 9–11, D–80377 München (Germany) Introduction Both epidemiological studies and experimental data point to the role of environmental pollutants as one of the factors responsible for the increasing prevalence of allergic diseases [1, 2]. Exposure to air pollutants can lead to structural and functional alterations of the mucosa and modulation of the immune response. In addition, air pollutants may directly act upon pollen or airborne allergens and modulate their allergenic potency [3]. To further address this question, pollen of birch (B), rye (R) and ash tree (A) was exposed to N02, S02 or 03. Subsequently, extracts were prepared and used at equal protein contents for skin prick tests and in vitro determination of histamine-releasing capacity. Materials and Methods Purified B, R or A pollen was commercially obtained. For pollutant exposure, pollen aliquots were kept in glass chambers (approximately 1 liter volume) for 4 h under continuous flow (2.5 1/min) of ambient air or ambient air containing 50,100,200 or 400 ppb N02,900 ppb SO, or 300 ppb 03. Subsequently, 105 pollen grains/ml were incubated in Tris-containing PBS (TCM buffer; pH 7.2) and extracted by gentle stirring for 1 h. After removal of the pollen, supernatants were tested for protein concentration by the Coomassie protein assay and adjusted to equal protein content for the respective pollen species after dilution. Cell suspensions containing basophils were obtained by dextran sedimentation outside the pollen season from peripheral blood of 8 individuals with seasonal rhinoconjunctivitis due to B (6/8) or R pollen (4/8), but not A pollen. Cells (2×106/ml) were incubated in duplicate with the extracts of native/pollutant-exposed B, R or irrelevant A pollen for 30 min at 37¤C. Histamine in the supernatants was measured by ELISA and expressed as the percentage of total histamine content after correction for spontaneous histamine release. Prick testing with the respective extracts (examiner blinded to the specification) was performed on the forearm of the 8 individuals. After 20 min, areas of wheal and flare response were documented on transparent tapes and