Immunomodulatory Activity Analyses of Cell-Free Supernatant of Lactobacillus plantarum LP299v Strain in RAW 264.7 Macrophage Cells

The human immune system is essential for defending the body against harmful internal and external elements; immunity includes innate and acquired immunity. Macrophages, the innate immune system's key components, are crucial for the clearance of dead cells and tumor cells, as well as foreign substances by triggering phagocytosis. They also play a role in the adaptive response with the cytokines and mediator molecules they secrete. Lactic acid bacteria (LAB), an important probiotics class, have a strong potential to improve host health and can be used as a functional food. There have been reports of certain LAB strains having immunostimulating effects. However, the effects of cell-free supernatants (CFS) gathered from some LAB strains on macrophage activation have become an important research area in recent years. This study's main objective was to characterize the immunostimulatory activities of Lactobacillus plantarum LP299v in the RAW 264.7 macrophage cell line. For this purpose, the immunomodulatory activity of CFS of the related strain was evaluated by MTT, neutral red assay, and Griess reaction respectively, in terms of proliferation, phagocytosis ability, and nitric oxide (NO) production parameters using the macrophage cell line. Studies have shown that this strain significantly increased proliferation, phagocytosis, and NO levels in RAW264.7 macrophage cells. When considered, these results suggest that the cell-free supernatant, obtained from Lactobacillus plantarum LP299v selected in this study, may be helpful for candidate compounds with immunostimulatory activity.