Nonopsonic phagocytosis of Lactobacilli by mice Peyer's patches' macrophages

The ingestion of lactobacilli is of great importance for the probiotic effect of host gut Peyer's patches (PPs) macrophages. The present study is in time focus on the investigation of the factors determining the ingestion of lactobacilli by PPs macrophages. Physicochemical properties of cell surface and adhesive property of nine Lactobacillus strains were examined in the present work. The association of the bacteria with PPs macrophage was checked with macrophage monolayers on coverslips. The influence of lactobacilli on macrophages phagocytic capacity was also investigated with a neutral red uptake assay in vitro. The results show that the macrophages could ingest lactobacilli in a strain dependent manner, and the most ingested strain is L. plantarum Lp6 compared to other tested strains, which displayed strain specific enhancement on the phagocytic activity of PPs macrophages. And there is no correlation between the physicochemical or adhesive properties of the cell surface and the ingestion. The association of L. plantarum Lp6 with PPs macrophage could be decreased by Protease K treatment. Surface proteins of L. plantarum Lp6 could promote the ingestion of fluorescent latex beads by PPs macrophages. In conclusion, the hydrophobicity of the cell surface might not be the key factor determining the association of lactobacilli with PPs macrophages. Cell surface proteins are the media for the binding L. plantarum Lp6 to macrophages.