Effects of orally administered viable Lactobacillus rhamnosus GG and Propionibacterium freudenreichii subsp shermanii JS on mouse lymphocyte proliferation

Immunomodulation by probiotics is a subject of growing interest, but the kn owledge of dose response and time profile relationships is minimal. In this study we examined the effects of Lactobacillus rhamnosus GG (LGG) and Prop ionibacterium freudenreichii subsp. shermanii JS (PJS) on the proliferative activity of murine lymphocytes ex vivo. Dose dependency was assessed by tr eating animals perorally with a low or a high dose (i.e., 10(9) or 10(12) v iable bacteria/kg of body weight) for 7 days. The lower dose levels of each strain appeared to enhance T-cell proliferation at the optimal concanavali n A (ConA) concentration (by 69 to 84%) and B-cell proliferation at the opt imal and supraoptimal concentrations of lipopolysaccharide (by 57 to 82%). B-cell proliferation was also enhanced by the high LGG dose (by 32 to 39%) but was accompanied by a marginal decrease in T-cell proliferation (by 8%) at the optimal ConA concentration. The time profiles of the immune response s were assessed after daily treatment,vith the higher dose for 3, 7, and 14 days. A significant decrease in basal lymphoproliferation (by 32 to 42%) w as observed,vith PJS treatment after the 3- and 7-day periods; however, thi s activity returned to control levels after 14 days of treatment, which als o resulted in significantly enhanced T-cell proliferation at optimal and su praoptimal ConA concentrations (by 24 to 80%). The ll-day LGG treatment als o enhanced the latter activity (by 119%). In conclusion, LGG and PJS have s pecific dose- and duration-dependent immunomodulatory effects on the prolif erative activity of B and T lymphocytes and may also reduce lymphocyte sens itivity to the cytotoxic effects of lectin mitogens.