Infectious Diseases and Molecular Genetics UnitsDepartments of,1 Traumatology,4 Plastic Surgery, Hospital Central de Asturias, Oviedo University Medical School, Oviedo,5 Biomedical Research Institute of Barcelona-Scientific Park, University of Barcelona, Barcelona, Spain,3 Infectious Diseases Section, Veterans Administration Medical Center and University of California, San Diego, California2
Received 11 August 2003/ Returned for modification 16 October 2003/ Accepted 9 March 2004
Polymorphonuclear neutrophils are critical for resolution of bacterial infections. In tissues, most of the neutrophils quickly die through apoptosis. Using propidium iodide DNA staining and DNA gel electrophoresis, we found that spontaneous apoptosis of neutrophils from patients suffering osteomyelitis (n = 52) was significantly decreased in relation to control neutrophils (n = 20) (40.2% ± 25.2% versus 54.5% ± 23.5%; P < 0.03). Incubation of neutrophils from normal volunteers with sera from patients with osteomyelitis reduced apoptosis from 79.1% ± 14.8% in control sera to 62.2% ± 18.7% in osteomyelitis sera. A significant increase of serum interleukin-6 (IL-6) and IL-1
was found in osteomyelitis (IL-6, 8.8 ± 11.9 pg/ml versus 1.8 ± 1.2 pg/ml in controls [P < 0.004]; IL-1
, 3.8 ± 6.4 pg/ml versus 1.0 ± 2.2 pg/ml in controls [P < 0.02]). No differences in the levels of other cytokines, such as tumor necrosis factor alpha, were found. There was an inverse correlation between IL-6 levels and neutrophil apoptosis (r = 0.855; P < 0.007), but this was not the case for other cytokines. The antiapoptotic effect of the osteomyelitis sera was reversed with anti-IL-6 antibodies (P < 0.03) and was reproduced with recombinant human IL-6 (P < 0.001). The longer life span of neutrophils in osteomyelitis induced by IL-6 could contribute to the tissue damage that occurs in these chronic bone infections.
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