Acute phase reactants and cytokine levels in unilateral community-acquired pneumonia

Bacterial infection of the lower respiratory tract initiates an acute inflammatory response. Regulation of the inflammatory response in bacterial pneumonia depends on a complex interaction between immune cells and inflammatory cytokines.

We investigated the initial levels of proinflammatory cytokines and acute phase reactants (APR), e.g. C-reactive protein (CRP), upon presentation of community-acquired pneumonia (CAP) in relation to clinical and laboratory indices of infection.

We prospectively studied 28 consecutive patients with unilateral CAP. Tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-1beta, IL-6 and IL-8 concentrations were measured by ELISA in both bronchoalveolar lavage (BAL) fluid and serum.

The concentrations of IL1-beta and IL-6 in BAL fluid were found to be significantly higher in the involved lung than those in either the uninvolved lung (p = 0.008 and p = 0.012, respectively) or serum (p = 0.002 and p = 0.025, respectively). Serum CRP concentrations were increased compared to those in the involved and uninvolved lung in BAL fluid (p = 0.000 and p = 0.000, respectively). In serum and BAL from involved lung, IL-6 concentrations were higher in the systemic inflammatory response syndrome (SIRS) group than in the non-SIRS group (p < 0.05), whereas CRP, TNF-alpha, IL-1beta and IL-8 concentrations showed no difference between SIRS and non-SIRS. There was no significant correlation between the acute physiology and chronic health evaluation II score and the cytokines.

Our results indicate that the CRP level is higher in the serum than in the BAL fluid in the lung, and that IL-6 is the most important cytokine for the determination of the severity of the disease.