This pilot study investigated the effects on salivary cytokine and sIgA before and after daily consumption of Lactobacillus casei Shirota (LcS) in nine healthy adult volunteers. Subjects were asked to consume two bottles each day of a fermented milk drink containing a total of 1.3×1010 live cells of LcS (Yakult), for 4 weeks. Volunteers were asked to avoid food and drink for at least 1 h before morning unstimulated saliva samples were collected over a 5 min period. Samples were collected at baseline, at week 1, 2 and 4 of LcS consumption, and 2 weeks after cessation of consumption. We found a significant transient increase in salivary IFN-γ levels, but were unable to detect IL-12, and an increase in salivary sIgA, IgA1 and IgA2 secretion. Baseline salivary IFN-γ was below the assay detection limits. However, at week 1, 4/9 subjects had detectable salivary IFN-γ levels, 8/9 (P<0.01) at week 2 and 3/9 at week 4. None had detectable IFN-γ levels at week 6. IFN-γ concentrations ranged from 35.3 to 92.0 pg/ml. There was a significant (P<0.02) increase in salivary sIgA secretion rate at week 4 (Fig. A). At week 6, the sIgA secretion rate was greater than baseline. The IgA1 secretion rate was significantly greater than baseline at week 4 (P<0.05) and week 6 (P<0.02) (Fig. B). The IgA2 secretion was also significantly increased at week 4 (P<0.05) and week 6 (P<0.01) (Fig. B) and the IgA1:IgA2 ratio significantly greater at week 2 (P<0.01). This pilot study demonstrates that LcS can induce increased salivary IFN-γ, sIgA, IgA1 and IgA2 secretion in healthy adults, which may improve mucosal immunity in the upper respiratory tract and provide health related benefits. A larger detailed study investigating cytokine networks, immunoglobulins and T cell responses in different immune system compartments in parallel with a placebo control group would define more rigorously and precisely the immunological effects of LcS (Yakult).
