IMMUNE-RESPONSE TO INFECTION - INTERLEUKIN-8 RELEASE FROM HUMAN NEUTROPHILS AFTER PHAGOCYTOSIS OF LISTERIA-MONOCYTOGENES AND YERSINIA-ENTEROCOLITICA

The release of interleukin-8 (IL-8) from human neutrophils was investi gated after their internalisation of the invasive bacteria Listeria mo nocytogenes and Yersinia enterocolitica. Three pairs of bacterial stra ins were used to study the influence of listeriolysin O, invasiveness and Yersinia virulence plasmid (pYV)-encoded proteins on neutrophil cy tokine synthesis. The neutrophils secreted IL-8 into the culture super nate after exposure to all strains tested. With L. monocytogenes, the virulence factor listeriolysin O had no effect on IL-8 secretion, wher eas a non-invasive mutant induced greater IL-8 release than the corres ponding invasive strain. With Y. enterocolitica, expression of virulen ce plasmid-encoded proteins appeared to be responsible for diminished IL-8 release. Northern blot analysis showed that the induced IL-8 rele ase was always accompanied by an enhanced level of cytoplasmic IL-8 mR NA. Cytokine priming of neutrophils with granulocyte macrophage colony -stimulating growth factor (GM-CSF), unlike granulocyte colony-stimula ting factor (G-CSF), led to further enhancement of IL-8 secretion indu ced after internalisation of the bacteria. Again, the increased IL-8 r elease, from GM-CSF primed neutrophils, was accompanied by an increase d level of cytoplasmic IL-8 mRNA. The results emphasise the role of IL -8 in neutrophil-mediated host defence mechanisms during the acute pha se of L. monocytogenes and Y. enterocolitica infection.