Contrasting inflammatory responses in severe and non-severe community-acquired pneumonia

Abstract

The objective of this study was to compare systemic and local cytokine profiles and neutrophil responses in patients with severe versus non-severe community-acquired pneumonia (CAP). Hospitalized patients with CAP were grouped according to the pneumonia severity index (PSI), as non-severe (PSI < 91 points) or severe (PSI ≥ 91 points). Blood and sputum samples were collected upon admission. Compared to non-severe CAP patients, the severe CAP group showed higher plasma levels of pro- and anti-inflammatory cytokines but in contrast, lower sputum concentrations of pro-inflammatory cytokines. Blood neutrophil functional responses were elevated in CAP patients compared to healthy controls. However, neutrophils from severe CAP patients showed reduced respiratory burst activity compared to the non-severe group. Results indicate that patients with severe CAP fail to mount a robust local pro-inflammatory response but exhibit instead a more substantial systemic inflammatory response, suggesting that a key driver of CAP severity may be the ability of the patient to generate an optimal local inflammatory response.

Fig. 1

Plasma cytokine profiles in non-severe and severe CAP patient groups. Blood samples were obtained shortly after admission to the hospital and assayed for the indicated cytokines and chemokines. Box plots depict the 25–75 % interquartile range and the horizontal bar depicts the median. *p < 0.05; **p < 0.01. For comparison, the broken horizontal line represents the mean plus one SD of the values for the healthy control group. Median and IQR data are summarized in Supplementary Table 1.

Fig. 2

Sputum cytokine profiles in non-severe and severe CAP patient groups. Sputum samples were obtained shortly after admission to the hospital and processed and assayed for the indicated cytokines and chemokines. Box plots depict the 25–75 % interquartile range and the horizontal bar depicts the median. *p < 0.05; **p < 0.01. Median and IQR data are summarized in Supplementary Table 2.

Fig. 3

Correlation between the neutrophil respiratory burst and plasma levels of CXCL10.