Serum levels of IL-6 in adult patients with moderate to severe asthma

Introduction: The role of IL-6 in the pathogenesis of bronchial asthma (BA) is still unclear. IL-6 has been viewed as an inflammatory marker, but recent studies suggest that it is also a regulatory cytokine. Aim: To analyse the serum levels of IL-6 in adult patients (Pts) with moderate to severe BA (AP). Method: We have evaluated 10 healthy controls (HC) and 30 AP out of exacerbation - 20 with chronic rhinitis (CR+) and 10 without rhinitis (CR-). Among the CR+ 16 Pts were allergic (AR) and 4 Pts were non-allergic (NR). Serum IL-6 levels were measured by ELISA method. We have evaluated C-reactive protein (CRP), white blood cells (WBC) and eosinophilic blood count (EBC). Results: We have observed a significant difference in IL-6 levels among AP (1.420 pg/ml) versus HC (0.340 pg/ml)(p<0.005) and among AR (2.306 pg/ml) and NR (2.149 pg/ml) versus CR- (0.846 pg/ml)(p<0.05, for both comparisons). IL-6 levels were elevated in AP with more than 1 exacerbation in the previous year (n=8) (2.130 pg/ml) as compared with other AP (0.990 pg/ml)(p<0.05). A significant negative correlation was established between IL-6 levels and ACT score (r=-0.405; p<0.05). We have found a significant positive correlation between IL-6 levels and CRP (r=0.367; p<0.05), WBC (r=0.409; p<0.05) and EBC (r=0.400; p<0.05). Conclusion: Higher serum levels of IL-6 were observed in AP as compared to HC and in AP with chronic rhinitis or Pts with history of more than 1 exacerbation in the previous year. Higher levels of IL-6 were associated with systemic inflammation and poor asthma control. These results suggest that IL-6 may have a role as a biomarker for persistent asthmatic inflammation and also for the prognosis of the disease.