ABSTRACT
Bronchial asthma is a complex inflammatory disease of the lung, although it is multifactorial in origin, the role of inflammatory process is believed to be the most popular hypothesis in pathogenesis of bronchial asthma. It is reported that Th2 cytokines play a crucial role in the pathogenesis of disease. The aim of this study was to evaluate the role of IL-13 in the pathogenesis of bronchial asthma. The study was carried out on 70 subjects out of which 50 were asthmatic patients and 20 were normal controls. Patients with bronchial asthma were further classified according to the National Asthma Education and Prevention Program [NAEPP] into 4 groups: mild persistent, moderate persistent, severe persistent, and intermittent. IL-13 serum levels were estimated in patients and controls by ELISA. Asthmatic patients showed a statistical significant elevation of serum IL-13 levels [mean = 76.8 +/- 66.4 pg/ml] as compared to controls [mean = 52.3 +/- 23.7 pg/ml]. When patients with different degrees of severity were compared, a significant increase in serum IL-13 was found in patients with intermittent asthma [mean = 105.7 +/- 104.6 pg/ml] as compared to those with mild [mean = 62.9 +/- 14.4 pg/ml] and severe persistent asthma [mean = 63.8 +/- 28.6 pg/ml]. Only patients with intermittent asthma showed a highly significant increase in serum IL-13 than controls. No statistically significant difference was found between patients not on steroid, patients on inhaled steroids and those on systemic steroids. A statistically significant increase in IL-13 serum levels was observed in patients not on steroids compared to normal controls. Also a statistically significant increase in BECs was found among asthmatic patients more than normal control and insignificant increase in severe persistent asthma more than other groups. In conclusion, IL-13 is a key cytokine with critical role in the immunopathogenesis of bronchial asthma. Steroids can down regulate IL-13, but inhaled steroids alone might not be able to abolish the airway remodeling process in asthmatics. Although patients with intermittent asthma are asymptomatic in between exacerbations, inflammation and remodeling are ongoing in their lungs