Immune Response of Healthy Adults to the Ingested Probiotic Lactobacillus casei Shirota

Daily ingestion of a probiotic drink containing Lactobacillus casei Shirota (LcS; 1.3 9 10(10) live cells) by healthy adults for (1) 4-week LcS, (2) 6-week discontinuation of LcS and (3) a final 4 weeks of LcS was investigated. There was a significant increase in expression of the T cell activation marker CD3+ CD69(+) in ex vivo unstimulated blood cells at weeks 10 and 14, and there was a significant increase in the NK cell marker CD(3+)CD16/56(+) in ex vivo unstimulated blood cells at weeks 4, 10 and 14. Expression of the NK cell activation marker CD16/56(+)CD69(+) in ex vivo unstimulated blood cells was 62% higher at week 10 and 74% higher at week 14. Intracellular staining of IL-4 in ex vivo unstimulated and PMA-/ionomycin-stimulated CD3(+)beta 7(+) integrin blood cells was significantly lower at weeks 10 and 14. Intracellular staining of IL-12 in ex vivo unstimulated and LPS-stimulated CD14(+) blood cells was significantly lower at weeks 4, 10 and 14. Intracellular staining of TNF-alpha in LPS-stimulated CD14(+) blood cells was significantly lower at weeks 4, 10 and 14. Mucosal salivary IFN-gamma, IgA1 and IgA2 concentrations were significantly higher at week 14, but LcS did not affect systemic circulating influenza A-specific IgA or IgG and tetanus-specific IgG antibody levels. In addition to the decrease in CD3(+) beta 7(+) integrin cell IL-4 and a reduced CD14(+) cell pro-inflammatory cytokine profile, at week 14 increased expression of activation markers on circulating T cells and NK cells and higher mucosal salivary IgA1 and IgA2 concentration indicated a secondary boosting effect of LcS.