Circulating interleukin 6 and interleukin 10 in community acquired pneumonia

Background-Inflammatory cytokine concentrations correlate with severity of sepsis. We hypothesised that patients with community acquired pneumonia (CAP) associated with systemic inflammatory response syndrome (SIRS) would have greater interleukin 6 (IL-6) production due to activation of the inflammatory cytokine cascade, matched by a significant anti-inflammatory cytokine response. Interleukin 10 (IL-10) was evaluated as a potential surrogate marker of severity of sepsis in CAP and age related impairment of the cytokine response was studied in elderly patients with CAP. Methods-Circulating immunoreactive IL-6 and IL-10 levels were measured in 38 patients with CAP subdivided into a group fulfilling the criteria for SIPS (n = 28) and a non-SIPS group (n 10) in a variety of age groups and correlated with APACHE II scores. Results-80% had circulating IL-6 levels (median 46.7 pg/ml, range 4.6-27 000) and 60% had circulating IL-10 levels (median 15.5 pg/ml, range 2.5-765). Concentrations of both were significantly increased in patients with SIPS compared with non-SIRS patients. Those with activation of the inflammatory cytokine cascade (IL-6 positive) produced more IL-10 than IL-6 negative patients. Older patients had a similar cytokine response. Both cytokines correlated positively with APACHE II scores. Conclusions-This is the first demonstration of circulating IL-10 in CAP. A greater counter-inflammatory response in patients with SIPS and in IL-6 positive patients suggests a potential immunomodulatory role for IL-10 in controlling the inflammatory cytokine response in CAP. IL-10 concentrations correlate with severity of illness in CAP and may be of prognostic importance. There is no age related impairment in the cytokine response.