Lactic acids bacteria are gram positive bacteria with similar physiologic and metabolic properties. They are primarily used in the food industry in the production of fermented items and in the pharmaceutical industry as delivery and expression systems. Due to their positive effects on human health, they are classified as probiotics. Many studies have concluded that lactic acid bacteria trigger the activation of monocytes, induce cytokine secretion and affect the activity of other immune cells. The effects of lactic acid bacteria are very diverse and dependent on the sort and the strain of bacteria, therefore the selection of a suitable strain is crucial to the success of a study. In vitro tests are used for searching candidates that possess suitable immunomodulatory properties.
In our research, we established a model for testing the effect of inactive lactic acid bacteria on the release of the pro-inflammatory cytokine interleukin 8 in THP-1 cells. The cytokines are secreted by several immune cells, while under the influence of a variety of stimuli, such as bacterial endotoxins. We used Lactococcus lactis as our model bacteria. The bacteria were deactivated by exposure to ultraviolet light. The increase of cytokine secretion was measured with enzyme-linked immunosorbent assay (ELISA). The quantity of the secreted interleukin 8 was then compared with the secretion after treatment of THP-1 cells with Escherichia coli, which served as a control. We used the THP-1 cell line as a model for primary monocytes, which is usually used for defining monocyte and macrophage activity in in vitro studies.
We established a test to determine the effect of lactic acid bacteria on the secretion of interleukin 8 from the THP-1 cell line. We confirmed that inactivated Lactococcus lactis modulates the secretion of interleukin 8 from the monocyte cell line THP-1.
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