AIM: To investigate whether the stimulation of peripher- al blood mononuclear cells (PBMNC) with the cell debris and cell extraction of different probiotic strains is similar or species specifi c. METHODS: Three strains of bifi dobacteria, 4 strains of lactobacilli, and E. coli nissle were sonicated and centri- fuged in order to divide them into cell extract and cell debris. PBMNC were separated by density gradient and incubated for 36 h with either the cell debris or the cell extract of single strains of probiotic bacteria in doses from 102 to 108 CFU/mL. Cell supernatants were taken and interleukin (IL)-10, IL-1β, and tumor necosis factor (TNF)-α were determined by ELISA. RESULTS: Depending on the species super-family, the strains had different stimulation patterns. Except for both L. casei strains, the cell extract of bifidobacteriaand lactobacilli had less stimulating capacity than cell debris, whereas the cell extract of E. coli nissle had simi- lar stimulating properties to that of the cell debris of the strain and significantly more stimulating capacity than that of bifi dobacteria and lactobacilli. The cell debris of bifi dobacteria stimulated more cytokine release than the cell debris of lactobacilli. The cell debris of lactobacilli did not have a stimulating capacity when lower concentra- tions were used. Neither cell extraction nor cell debris had an inhibitory effect on the production of the tested cytokines by stimulated PBMNC. CONCLUSION: The incubation of probiotic strains, which have been used in clinical trials for inflammatory diseases, with immunocompetent cells leads to different species specifi c reactions. High IL-10 response to cell de- bris of bifi dobacteria and E. coli nissle can be found. This corresponds to positive effects of bifi dobacteria and E. coli nissle in clinical trials for inflammatory bowel disease compared to negative outcomes obtained with lactoba- cilli. A: To investigate whether the stimulation of peripheral blood mononuclear cells (PBMNC) with the cell debris and cell extraction of different probiotic strains is similar or species specifi c. METHODS: Three strains of bifi dobacteria, 4 strains of lactobacilli, and E . PBMNC were separated by density gradient and incubated for 36 h with either the cell debris or the cell extract of single strain of probiotic bacteria in doses from 102 to 108 CFU / mL. Cell supernatants were taken and interleukin (IL) -10, IL-1β, and tumor necrosis factor (TNF) -α were determined by ELISA. RESULTS: Depending on the species super-family, the had had different stimulation patterns. Except for both L. casei strain, the cell extract of bifidobacteria and lactobacilli had less stimulating capacity than cell debris, while the cell extract of E. coli nissle had simi- lar stimulating properties to tha t of the cell debris of the strain and significantly more stimulating capacity than that of bifi dobacteria and lactobacilli. The cell debris of bifi dobacteria stimulated more cytokine release than the cell debris of lactobacilli. The cell debris of lactobacilli did not have a stimulating capacity when Neither cell used nor cell debris had an inhibitory effect on the production of the tested cytokines by stimulated PBMNC. CONCLUSION: The incubation of probiotic strains, which have been used in clinical trials for inflammatory diseases, with immunocompetent cells Leads to different species specifi c reactions. High IL-10 response to cell de- bris of bifi dobacteria and E. coli nissle can be found. This corresponds to positive effects of bifi dobacteria and E. coli nissle in clinical trials for inflammatory bowel disease compared to negative outcomes obtained with lactoba- cilli.