Eleven strains of lactobacilli were tested for their ability to induce the murine macrophage-like cell line J774.1 to secrete cytokines. Some of the bacteria tested induce the production of interleukin(IL) 6, IL-12, and tumor necrosis factor a (TNF-alpha) by J774.1 cells. Seven strains also induced the production of IL-10. However, no IL-1beta was produced. Lactobacillus acidophilus TMC 0356 significantly induced the production of more IL-6, IL-10, IL-12, and TNF-alpha than the other bacteria tested (p < 0.0001; ANOVA). These results suggest that lactobacilli can activate macrophages to secrete both inflammatory and anti-inflammatory cytokines. Selected strains might be used to bring about pro or antiinflammatory immune reactions.

There have been few studies on the probiotic activity of Lactococcus strains although they are commonly used as starter bacteria in manufacturing many kinds of fermented dairy products. Nine strains of the genus Lactococcus were examined for their probiotic properties, such as adherence to human enterocyte‐like Caco‐2 cells and tolerance to acid and bile. Six strains were adhesive and the highest adhesion was observed with Lactcoccus lactis ssp. lactis NIAI527. This strain adhered to the microvilli of cells as observed by scanning electron microscopy and also tolerated low pH and bile. These properties should make strain 527 a potential new probiotic strain.

SUMMARYWe demonstrate the induction of antigen-speci®c interleukin-10 (IL-10)-secreting cells in murine Peyer's patches (PPs) after low-dose b-lactoglobulin (BLG) feeding. In addition, we show that PP cells can inhibit the T-cell proliferative response in vitro as well as T-cell-mediated in¯ammation in vivo. The active suppression mediated by these regulatory cells was seen only within a narrow range of antigen dosage (feeding), with the most prominent effect at 5r1 mg BLG. On either side of this range, T-helper 1-like cytokine responses were observed when PP cells were stimulated with antigen in vitro. This result correlated with reduced production of regulatory cytokines as well as reduced activity of bystander suppression. We found that changes in IL-10 production correlated inversely with changes in interferon-c production. Inhibitory effects mediated by CD4 + PP cells were partially neutralized by antibodies to IL-10 and transforming growth factor-b. Interestingly, the generation of such regulatory cells after low-dose BLG feeding exhibited organ dependence. Among spleen, lymph node and PP cells derived from orally tolerized mice, PP cells were the most effective in promoting bystander suppression in the presence of BLG, indicating the signi®cance of PPs as an inductive site for antigen-speci®c regulatory cells upon induction of low-dose oral tolerance. Moreover, PP cells from mice fed 5r1 mg BLG were shown to suppress a BLG-speci®c delayed-type hypersensitivity response induced in footpads, suggesting that IL-10-secreting PP cells regulate systemic in¯ammation.

Abstract:To characterize the ability of bifidobacteria to affect the production of macrophage-derived cytokines, a murine macrophage-like cell line, J774.1, was cultured in the presence of 27 strains of heat-inactivated bifidobacteria. Bifidobacterium adolescentis and B. longum, known as adult-type bifidobacteria, induced significantly more pro-inflammatory cytokine secretion, IL-12 and TNF-␣, by J774.1 cells, than did the infant-type bifidobacteria, B. bifidum, B. breve, and B. infantis (P 0.01). In contrast, B. adolescentis did not stimulate the production of anti-inflammatory IL-10 from J774.1 cells as the other tested bacteria did. The results suggest that the adult-type bifidobacteria, especially B. adolescentis, may be more potent to amplify but less able to down-regulate the inflammatory response.

The effects of oral administration of a lactococcal strain on physiological changes associated with ageing were investigated using senescenceaccelerated mice (SAM). SAM develop normally, but then show an early onset and irreversible advancement of senescence. SAMP6 is a SAM strain that develops osteoporosis with ageing. Oral administration of heat-killed Lactococcus lactis subsp. cremoris H61 (strain H61) to aged SAMP6 mice was associated with reduced bone density loss, a suppression of incidence of skin ulcers and reduced hair loss, compared with controls. Spleen cells from mice fed strain H61 produced more interferon-g and IL-12 than those from control mice, suggesting that administration of strain H61 altered immune responses. The numbers of viable cells of Bifidobacterium sp., Bacteroides sp. and Enterococcus sp. in faeces were similar for mice fed the strain H61 and control diets, but counts for Staphylococcus sp. were significantly lower (P,0·05) in mice fed strain H61. Mice fed strain H61 had similar serum concentrations of thiobarbituric acid-reactive substances as in controls, indicating a lack of effect on lipid peroxidation status. Administration of living cells of strain H61 or fermented milk containing strain H61 was also associated with a suppression of incidence of skin ulcers and reduced hair loss. These results indicate that oral administration of strain H61 has the potential to suppress some of the manifestations associated with ageing.