Introduction: Bioaerosol-related airborne dermatitis was described in farmers and sewage workers. Bioaerosols consist of Gram-negative bacteria and microvesicles (MV) emerging from disrupted bacteria.
Aims: To assess proinflammatory properties of microvesicles.
Material and methods: MV were produced through disruption of the bacterial wall of the Gram-negative bacterium Pantoea agglomerans. Peripheral blood mononuclear cells (PBMC) of five healthy volunteers were cultured for 6 h, 24 h, 3 days, and 5 days with MV at concentrations 0.48 - 1500 µg/ml. The following variables were observed: secretion of IFN-gamma and TNF-alpha (ELISA and ELISPOT assays), intensity of cell proliferation (LPT), expression of surface markers CD8, CD14, CD16, CD25, CD69, CD80, CD83, HLA-DR, the apoptosis marker Annexin V, and PI permeability (flow cytometry).
Results: After 24 hours, a clear dose-dependent response to MV was seen for IFN-gamma production starting with the lowest MV concentration of 0.48 µg/ml (p=0.042). A significant (p=0.05) increase in the production of TNF-alpha was observed after 3 days at MV concentrations of 300 µg/ml or higher. On the LPT, there was a clear and significant dose-response to MV after 5 days (p=0.001). Regarding expression of cell surface markers, the only phenomenon seen in all donors was the decrease in the number of CD14(+)CD83(+) cells with increasing MV concentration (probably due to increased MoDC maturation).
Conclusions: Microvesicles are biologically active in PBMC cultures in a dose-dependent manner. IFN-gamma production was increased already at lowest MV doses tested. These results explain clinical observations on the proinflammatory effect of bioaerosols on the skin.
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Document created: 17 October 2008, last updated: 4 July 2010.