Leucocyte response and anti-inflammatory cytokines in community acquired pneumonia

Background-In the host defence of the lung neutrophils (PMN) play a central role. Apart from antimicrobial properties, recent data indicate that PMN a lso exert anti-inflammatory effects by stimulation and release of cytokine antagonists such as interleukin-1 receptor antagonist (IL-1ra). Methods-Cytokine release from lipopolysaccharide stimulated whole blood was studied in 18 patients with community acquired pneumonia (CAP) and severe co-morbidities at admission and after 24 hours. Release of IL-1ra, interleu kin-l beta (IL-1 beta), tumour necrosis factor alpha (TNF alpha), soluble T NF receptor type I (sTNF-RI), and IL-8 was determined by ELISA. Results-The mean (SD) leucocyte level at admission was 12.5 (4.1)/nl. There was a significant correlation between the release of anti-inflammatory cyt okines such as IL-1ra and sTNF-RI and the leucocyte count at admission and after 24 hours. Additional in vitro experiments showed that co-incubation o f peripheral blood mononuclear cells with autologous PMN led to a marked do se dependent increase in IL-1ra and sTNF-RI release. Conclusion-These results indicate that PMN may be responsible for the incre ase in anti-inflammatory cytokines in CAP. Strategies to increase neutrophi l counts may exert beneficial effects, not only by augmenting the antimicro bial activity but also by modulating the inflammatory cytokine response.