The aim of the present work was, first, to analyze the apoptotic effect in vitro of sonicated preparations of selected strains of lactic acid bacteria on normal and tumor human lymphocytes. Incubation with bacterial samples led to a relevant time-dependent apoptotic cell death of Jurkat cells but not normal human peripheral blood lymphocytes. Lactobacillus brevis (CD2) samples were more efficient in inducing apoptosis of Jurkat cells than were samples of Streptococcus thermophilus (S244). In an attempt to characterize the mechanisms underlying these effects, we found that the apoptotic death-inducing ability of S244 preparations could be attributed to the ability of high levels of neutral sphingomyelinase activity to generate relevant amounts of ceramide, a known apoptotic death messenger, in Jurkat cells. On the other hand, our results indicate that apoptosis induced by CD2 samples could also be associated with high levels of arginine deiminase activity, which in turn was able to downregulate polyamine synthesis in Jurkat cells.
