Lipopolysaccharide of Haemophilus influenzae induces interleukin-5 mRNA expression in human peripheral blood mononuclear cells

Haemophilus influenzae is the bacterial species most often isolated from sp utum of patients with chronic obstructive pulmonary disease (COPD), In this study, we examined the induction of interleukin-5 (IL-5) mRNA expression i n human peripheral blood mononuclear cells (PBMC) stimulated with lipopolys accharide (LPS) from H, influenzae to try to predict the effect of H, influ enzae infection on the eosinophilic inflammation in COPD, Detection of IL-5 mRNA by RT-PCR showed that LPS from H, influenzae induced IL-5 mRNA expres sion in PBMC at a concentration of 1 mug/ml. Furthermore, the level of expr ession of IL-5 mRNA induced by LPS correlated with the amount of IL-5 prote in in the culture supernatant. Inhibition of LPS-induced IL-5 mRNA expressi on by anti-CD14 antibody and diminution of this in a CD3(+)-cell-depleted f raction of PBMC, respectively, suggested that CD14 molecules were required for the increase in IL-5 mRNA and that T lymphocytes were the principal sou rce of IL-S mRNA expression in PBMC, Briefly, the IL-5 mRNA expression indu ced by LPS would be based on LPS-activated monocytes interacting with T lym phocytes to produce IL-5, These results may explain the role that colonizat ion with H, influenzae plays in eosinophilic inflammation in patients with COPD.