Elevated neopterin levels in non-allergic asthma

Abstract

Neopterin is synthesized by human monocyte-derived macrophages upon stimulation with interferon- (IFN- ). Measurement of neopterin concentration is useful to monitor cell-mediated (Th1-type) immune activation. In this study, we aimed to analyze the behaviour of neopterin in long lasting asthma considering its role as a marker of the Th1 environment and to establish the distinction between patients belonging either to the allergic or the non-allergic population, particularly in the elderly where asthma is often under diagnosed. Therefore we evaluated allergic parameters such as skin prick tests, IgE and hemogram (eosinophils count), and we compared our findings with neopterin values found in an age-matched control population. A group of individuals older than 65 was selected. It included 64 asthmatic patients (mean age 72±5 years) and 41 healthy individuals (mean age 79±7 years). In our study population, 42 patients presented positive skin tests, mainly to house dust mites. All patients were clinically stable and presented an average percentage of predicted forced expiratory volume in the first second (FEV1) of 73.6±25.3 and predicted median expiratory flow percentage (MEF50) of 38.8±26.7. Blood cell counts showed statistically different mean values of eosinophils between allergic and non-allergic controls (5.42±4.7% versus 2.8±2.8%; p < 0.04). IgE values were increased in allergic asthmatic patients when compared with non-allergic asthmatic patients (493.2±549.8 IU/ml versus 85.3±194.4 IU/ml; p = 0.000). Allergic asthmatic patients presented mean neopterin levels similar to those found in the control group (2.4±2.8 ng/ml versus 2.1±1.9 ng/ml). In contrast, in non-allergic asthmatic patients these values were higher when compared with the control group (4.0±4.7 ng/ml versus 2.1±1.9 ng/ml). Neopterin levels were lower in allergic asthmatic patients when compared with non-allergic asthmatic patients (2.4±2.8 ng/ml versus 4.0±4.7 ng/ml). Within asthmatic patients, those with higher neopterin values (>2.1 ng/ml) presented lower mean IgE values (IgE≤336.58 IU) than those with lower neopterin values (≤2.1 ng/ml) who presented mean IgE values of 402.70 IU. Our initial findings may lead to a better understanding of the immunoinflammatory pathways in asthma. Further studies will probably show that serum neopterin could became a useful marker for asthma classification including in elderly patients with long lasting disease.