Background: The aim of this study was to test the hypothesis that the chronic inflammatory process present in chronic obstructive pulmonary disease (COPD) is due to a defective endogenous anti-inflammatory mechanism.
Methods: Systemic levels of the anti-inflammatory mediators soluble interleukin 1 receptor II (sIL-1RII), soluble tumour necrosis factor receptor p55 (sTNF-R55) and sTNF-R75, and of C reactive protein (CRP) and lipopolysaccharide binding protein (LBP) were analysed in 55 patients with stable COPD (median forced expiratory volume in one second (FEV(1)) 34% predicted (range 15-78)) and compared with levels in 23 control subjects. In addition, changes in these mediators were studied in 13 patients with COPD (median FEV(1) 34% predicted (range 19-51)) during the first 7 days in hospital with an exacerbation of the disease.
Results: Patients with stable COPD were characterised by a systemic inflammatory process indicated by an increased leucocyte count (7.2 (4.7-16.4) v 4.8 (3.5-8.3) x 10(9)/l), raised levels of CRP (11.8 (1.1-75.0) v 4.1 (0.6-75.0) microg/ml) and LBP (45.6 (8.1-200.0) v 27.9 (14.1-71.5) microg/ml), and moderate increases in both sTNF-Rs. In contrast, the sIL-1RII level did not differ between patients and controls (4.53 (2.09-7.60) v 4.63 (3.80-5.93) ng/ml). During treatment of disease exacerbations, systemic levels of both CRP (at day 3) and LBP (at day 7) were significantly reduced compared with day 1, whereas sIL-1RII levels increased.
Conclusions: These data suggest an imbalance in systemic levels of pro- and anti-inflammatory mediators in patients with stable COPD. The increase in the anti-inflammatory mediator sIL-1RII during treatment of exacerbations may contribute to the clinical improvement.