The effects of live Streptococcus pneumoniae and tumor necrosis factor-α on neutrophil oxidative burst and β2-integrin expression

Abstract

Objective. To study the effects of TNF-α and live Streptococcus pneumoniae on human neutrophil oxidative burst and β2-integrin expression using flow cytometry. Methods. Six clinical isolates of S. pneumoniae (serotypes 3, 19A, 22F, 6A, 33F and 9N) from patients with bacteremic pneumonia or upper respiratory tract infections were studied. Whole blood was incubated either alone, with TNF-α or with S. pneumoniae or with both TNF-α and pneumococci at a ratio of one neutrophil per 1-5 bacteria. After 30 min of incubation, the tubes were put into ice, fixed and analysed. Results. S. pneumoniae caused an increase in oxidative burst but not greater than that caused by TNF-α alone. When whole blood was preincubated with TNF-α for 30 min before the addition of pneumococci, a further increase in the oxidative burst response was seen. The variation in CD11b expression was not significant. Both S. pneumoniae and TNF-α caused increases in CD18 expression. The addition of TNF-α directly with the bacteria caused no further increase, but preincubation of blood with TNF-α 30 min before the addition of the bacteria caused a significant increase in CD18 expression. Conclusions. Live S. pneumoniae stimulates polymorphonuclear leukocytes to produce an oxidative burst and increases expression of CD18, and these effects are enhanced by TNF-α.