The Serum and Sputum Levels of Interlukin - 17 in Patients with Asthma

Association of asthma with Type 2 T- helper system is well realized. Recent clinical evidence show that acute, sever exacerbations of asthma are associated with recruitment and activation of neutrophils in the airways. The lymphocytes T helper 17 (Th17) cells can probably recruit neutrophils to an inflammatory site through producing IL-17. The objective of this study was to investigate the level of interlukin-17(IL-17) in serum and sputum of asthmatic subjects. Also, the study aimed at evaluating the correlation between concentrations of IL-17 and the frequency of inflammatory cells in the sputum of asthma at different stages. Fifty newly diagnosed asthmatics and 12 non-asthmatics healthy subjects, as the control group, entered this prospective study. None of them reported any recent history of infection and steroid usage. Then, samples from venous blood and sputum (Induced by Hypertonic saline %5) were obtained. The severity of asthma was classified according to GINA 2004 guidelines. The Concentrations of IL-17 in serum and supernatant of induced sputum were determined by ELISA method. Total serum IgE level was also determined in order to classify asthmatic subjects into allergic and non-allergic groups.As the findings of the study suggest, serum IL-17 level was significantly higher in asthmatic patients than in the normal control subjects (78.8 ±58.7 vs 17.7 ± 2.4 pg/dl, P=0.025). IL-17 was found to be significantly increased in sputum of the subjects with asthma, as compared to the control subjects (31.6 ±20.9 vs 21.5± 16.6 pg/dl, P=0.012). In addition, allergic and non-allergic asthmatic patients showed a significantly higher concentration level of serum IL-17 than the normal controls (80.8±50.3, P=0.023 and 102.7±43.6, P= 0.002vs 17.7 ±2.4 ng/ml). But, it was found that the levels of both serum and sputum IL-17 in the allergic asthma group were not significantly higher than those in the non –allergic asthmatics. Moreover, serum IgE level was significantly higher in allergic asthmatic patients than non –allergic asthmatic and normal control subjects (295.8± 168 vs. 99.1±90.0 P=0.001 and 49.7±41.8, P=0.001). The results further revealed that macrophage was decreased in sputum but neutrophil and eosinophil were significantly increased. However, the increase of IL-17 was not correlated with asthma severity. Besides, there was no significant difference between allergic and non- allergic asthmatic subjects, in terms of IL-17.We propose that IL-17 may play a role in the airway inflammation of asthmatics by recruiting neutrophils into the lung, no matter if they are suffering from allergic or non-allergic asthma.