Effect of Bifidobacterium bifidum DSM 20082 cytoplasmic fraction on human immune cells

The objective of the present study was to determine the effect of the soluble cytoplasmic fraction from Bifidobacterium bifidum DSM 20082 (Bb) lysate on peripheral blood T cells. In peripheral blood mononuclear cells of healthy subjects, cytotoxic activity, proliferation, apoptosis, and up-regulation of CD8 or CD4 molecules in T cells were examined. When peripheral blood mononuclear cells were stimulated with Bb lysate, the main effect was observed in CD8+ cells as a significant increase of CD8 molecules in a dose-dependent manner, and this behavior was observed at 24, 48, and 72 h after stimulation; in contrast, stimulation with Bb lysate showed no effect on the up-regulation of CD4 molecules in T helper cells. Further Bb lysate did not induce proliferation activity in either CD8+ or CD4+ cells. Bb lysate induced activation of CD8+ cytotoxic activity against autologous monocytes. Around 80% of the cells stimulated with Bb lysate were positive to peanut agglutinin (PNA), suggesting that the stimulated CD8+ cells corresponded to activated/effector cellular populations. When apoptosis was determined, there were no differences between stimulated and non-stimulated cells. Our results indicate that Bb lysate is able to increase cytotoxic activity of peripheral CD8+ cells, without affecting lymphocyte survival.