Systemic cytokine levels in community-acquired pneumonia and their association with disease severity

Pro-inflammatory and anti-inflammatory cytokines are important mediators in the host response to infection. In contrast to the pro-inflammatory cytokines little is known about anti-inflammatory cytokines in community-acquired pneumonia (CAP) and their relation to disease severity. Circulating levels of three pro-inflammatory cytokines (interleukin (IL)-1beta, IL-6 and tumour necrosis factor (TNF)-alpha) and two anti-inflammatory cytokines (IL-10, IL-1 receptor antagonist (IL-1ra)) were measured using an enzyme immunoassay on admission, day 3 and day 5 in 24 patients with CAP. The modified British Thoracic Society (BTS) prognostic rule and Acute Physiology and Chronic Health Evaluation (APACHE) II score were used to assess disease severity. IL-6, TNF-alpha, IL-10 and IL-1ra concentrations were detected in most patients on admission and decreased significantly on day 3 and day 5 in all survivors. A significant difference between the BTS high-risk and low-risk groups was only found for IL-6 (median (range) 477 pg x mL(-1) (7.6-1402 pg x mL(-1)) versus 81.6 pg x mL(-1) (0-943 pg x mL(-1)); p<0.05). IL-6 also correlated with the APACHE II scores on admission. Concentrations of anti-inflammatory cytokines were elevated on admission in community-acquired pneumonia but they did not correlate with disease severity scores.