The stimulatory effects of different purified lipopolysaccharide (LPS) preparations from E. coli, S. typhosa, P. aeruginosa, and K. pneumoniae on cytokine and chemokine production were measured in whole blood assays by ELISA. Incubation of 0.5 ml whole blood with 10 ng/ml E. coli and S. typhosa resulted in a time-dependent production of TNF-alpha, IL-1beta, IFN-gamma, IL-10 and MCP-1. K. pneumoniae, however, showed preferential effects on IL-1beta, IL-10 and MCP-1 production with less potent effects on TNF-alpha and IFN-gamma. LPS derived from P. aeruginosa showed a similar potency to other LPS preparations on MCP-1 production, yet completely failed to elicit the production of other cytokines. To further investigate potencies of the different LPS preparations, mediator production was determined following stimulation with agonist concentrations of 0.1 ng and 1000 ng per ml over a 24 h time period. Dose-response curves were obtained with LPS derived from E. coli, S. typhosa and K. pneumoniae on all mediators apart from IL-1beta and MCP-1. Most strikingly though, was the ability of LPS derived from P. aeruginosa to selectively elicit a significant dose-response effect on MCP-1 production, despite its very weak stimulatory effects on all other cytokines. These data imply that the bacterial origin of different LPS preparations can exhibit disparate effects on inflammatory mediator production. Furthermore, the potent, selective dose-response effect of P. aeruginosa LPS on MCP-1 production could help to explain the preponderance of a relentless inflammatory cellular infiltrate in diseases such as cystic fibrosis (CF).