High- and low-level cytokine induction in human peripheral blood mononuclear cells by different Borrelia burgdorferi strains

In this report we have compared the ability of 14 Borrelia burgdorferi sensu lato isolates to stimulate monocytes. From these isolates, all three human pathogen genospecies were represented. To determine the stimulatory activity of the different strains, interleukin-1β (IL-1β) was measured in the supernatant of monocyte cultures. This was achieved with borrelial strains in a ratio of 10 bacteria to 1 monocyte. In the majority of strains the stimulation induced a release of about 8000 pg/ml IL-1β, whereas four strains (B31, 297, EB3, 1/B29) induced more than 18000 pg/ml IL-1β. We could, therefore, define two groups: low-level inductors and high-level inductors for IL-1β. The strains in the defined groups could not be ascribed to one distinct genospecies or a biological source. Further experiments confirmed the same differential release for tumor necrosis factor-α, but not for IL-6. Studies on IL-1β indicated that high- and low-level release of cytokine was due to differences in protein synthesis. Received: 30 January 1996