Production of IL-1 beta and TNF-alpha by peritoneal macrophages depends on the bacterial species and the inoculum.

Peritoneal macrophages (PMs) are very potent producers of proinflammatory stimuli, such as interleukin (IL)-1 beta and tumor necrosis factor (TNF)-alpha. After contact with invading micro-organisms, PMs produce different cytokines, both pro- and anti-inflammatory. Therefore, they are crucial in the regulation of inflammatory events. The aim of this study was to investigate whether the production of IL-1 beta and TNF-alpha is dependent on the bacterial species used. PMs were harvested from spent peritoneal dialysis effluent and subsequently stimulated with five strains of bacteria in two different concentrations. After 24 hours of stimulation, supernatants were harvested and analyzed for both IL-1 beta and TNF-alpha content. IL-1 beta was measured with a commercial ELISA, and TNF-alpha was determined with a bioassay. Both the IL-1 beta and the TNF-alpha production were species-dependent. One strain of Staphylococcus aureus and one strain of Staphylococcus epidermidis induced a markedly higher response in both IL-1 beta and TNF-alpha than the other species. This response was also dose-dependent, and this holds true for all species. In conclusion, the IL-1 beta and TNF-alpha response by PMs is both species- and dose-dependent.