The present study was designed to investigate the effect of membrane proteoglycans (MPG) from Klebsiella pneumoniae on production of the chemotactic cytokine, IL-8, and monocyte chemotactic protein (MCP) by human peripheral blood monocytes. Exposure of human peripheral blood monocytes to MPG in vitro induced high levels of mRNA transcripts for IL-8 and MCP, as assessed by Northern blot analysis. Cytokine gene expression was associated with the production of chemotactic activity in the supernatants. The levels of IL-8 and MCP expression induced by MPG were comparable with those elicited by LPS. Induction of chemotactic cytokines in mononuclear phagocytes may play a role in the immunomodulatory activity of MPG.