Lactobacillus plantarum 299: beneficial in vitro immunomodulation in cells extracted from inflamed human colon.

Background And Aim: The present study determined the pattern of cytokine secretion (interleukin [IL]-1beta, tumor necrosis factor [TNF]-alpha, interferon [IFN]-gamma and IL-10) and their cellular sources in mononuclear cells isolated from colonic mucosa from normal and ulcerative colitis (UC) in response to probiotic and pathogenic bacteria.

Methods: Mononuclear cells were extracted from normal and active UC colonic mucosa and incubated with pure sonicates of probiotic, commensal, and pathogenic bacteria. Cytokine secretion was measured in culture supernatant and intracellular cytokine staining measured using fluorescent-activated cytometry.

Results: In mononuclear cells isolated from normal mucosa, significant increases in mean IL-1beta were observed with enteropathogenic Escherichia coli (286.3 +/- 138.7 pg/mL P < 0.05) and E. coli (440.5 +/- 194.0 pg/mL P < 0.01) compared with unstimulated control cells (16.7 +/- 4.8 pg/mL). In contrast, mononuclear cells isolated from active UC mucosa produced significant increases in mean IL-1beta in response to stimulation with Salmonella dublin (230.5 +/- 38.8 pg/mL P < 0.05), enteropathogenic E. coli (231.7 +/- 45.3 pg/mL P < 0.05) and E. coli (465.4 +/- 60.2 pg/mL P < 0.001) compared with unstimulated control cells (60.7 +/- 17.1 pg/mL). Escherichia coli also produced significant mean increases of TNF-alpha and IFN-gamma compared with unstimulated control cells. No significant increases in IL-1beta, TNF-alpha or IFN-gamma were observed with Lactobacillus plantarum in cells derived from normal or inflamed mucosa. Strikingly, incubation of L. plantarum with mononuclear cells isolated from active UC mucosa resulted in significant increases of mean IL-10 (327 +/- 53.5 pg/mL, P < 0.05) compared with unstimulated control cells (29.7 +/- 13.2 pg/mL). Intracellular cytokine staining confirmed T-cell and macrophage IL-10 production after L. plantarum stimulation.

Conclusions: Lactobacillus plantarum demonstrates beneficial immunomodulatory activity by increasing IL-10 synthesis and secretion in macrophages and T-cells derived from the inflamed colon. This may provide a mechanism through which probiotic bacteria ameliorate inappropriate inflammation and induce tolerance.