No abstract

It has been known for years that commensal bacteria in our intestines play an important role metabolizing digesta in the lumen and in so doing provide an additional source of nutrients. The composition of commensal bacteria is highly stable and characteristic for an individual over time but does appear to vary considerably between individuals.1 Dietary changes, stress and consumption of antibiotics can disturb the balance of commensal bacteria and a healthy balance can be reestablished with probiotic supplementation. In recent years, lactic acid bacteria (LAB) have been marketed by the dairy industry as an important natural bacterium for the maintenance of gut health. Other Gram-positive bacteria, such as Streptococcus thermophilus and S. faecalis, have been used as probiotics for farm animals.2 Although not officially recognized as probiotic bacteria, S. thermophilus and Staphylococcus carnosus are often used as starter cultures in the production of cheeses and salami and are normally consumed in very large numbers in our diets. These bacteria may also have a biological impact on the consumer. To qualify as a probiotic, bacterial strains must satisfy a number of criteria, including the ability to survive in the gastrointestinal tract.4 Bifidobacterium species and LAB are naturally commensal bacteria in the small and large intestines. These bacteria protect the host against potential pathogens by competitive exclusion and also by the production of antibacterial agents known as bacteriocins. It has only been recently shown that another mechanism whereby probiotic bacteria may provide a health benefit is by modulating immune responses. The immune-stimulating effect of LAB has been investigated using several animal experimental models. Lactobacillus casei strain Shirota (LcS) is a strain of LAB that was selected for its specific biological activity in man and animals. LcS is widely used in the production of probiotic dairy products and also as a food ingredient in Japan and in Europe, because of its proven safety and functional characteristics. To examine a role for probiotic bacteria in the modulation of immune responses, we describe, in the present paper, recent studies that have been carried out to demonstrate that some probiotic bacteria appear to have the ability to affect innate, humoral and cellular arms of the immune system. Effect on innate immunityNatural killer (NK) cells are large granular lymphocytes derived from bone marrow and these cells display non-MHCrestricted cytotoxicity against a variety of tumours. It is well recognized that NK cells act as cytolytic effector cells of the innate immune system. Recent studies have revealed that NK cells, including gamma/delta T cells, also regulate the Summary For many years, probiotic bacteria have been known to confer health benefits to the consumer. One possible mechanism for this may be the ability of probiotic bacteria to modulate immune responses. Oral administration of Lactobacillus casei strain Shirota (LcS) has been found to enhance innate immunity by...

We investigated the effect of oral feeding of heat-killed Lactobacillus casei strain Shirota on immunoglobulin E (IgE) production in mice. The strain was orally administered to BALB/c mice that had been preinjected intraperitoneally with ovalbumin, and the level of IgE in serum was determined. Results indicated that the oral feeding of L. casei strain Shirota was effective in inhibiting IgE production in serum, and the IgE production in response to ovalbumin was significantly inhibited in the mice. The in vitro production of IgE by the spleen cells from mice fed L. casei strain Shirota in response to restimulation with ovalbumin was inhibited in contrast to that of spleen cells from the control group. We also examined the pattern of cytokine production by spleen cells from mice fed L. casei strain Shirota followed by restimulation with ovalbumin in vitro. In the mice fed L. casei strain Shirota, the production by the spleen cells of Th1 cell-associated cytokines, such as interferon-gamma and interleukin-2, was higher than that by the spleen cells from the control group. In contrast, the production of Th2 cell-associated cytokines, such as interleukin-4, interleukin-5, interleukin-6, and interleukin-10, by spleen cells in the group fed L. casei strain Shirota was lower than that by the cells from the control group. Furthermore, the interleukin-12 production of the spleen cells from mice fed L. casei strain Shirota was also higher than that of the control group.

Prevention of onset in an insulin-dependent diabetes mellitus model, NOD mice, by oral feeding of Lactobacillus casei. APMIS 105: [643][644][645][646][647][648][649] 1997.The effects of Lactobacillus casei (LC) on the onset of diabetes in an insulin-dependent diabetes mellitus model, nonobese diabetic (NOD) mice, were examined. From the age of 4 weeks, female NOD mice were fed a diet of either standard laboratory chow (n= 12) or the same chow containing 0.05% weight heat-killed cells of LC (n= 12), and the onset of diabetes was thereafter recorded. The incidence of diabetes in the control group (10112) was significantly higher than that in the LC-treated group (31 12) (p