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    The relationship between lactic acid bacteria and gastrointestinal immunity

    Author:Aomron   Time:2017-03-06   Hits:788

        After crossing the gastric acid barrier, lactic acid bacteria maintain their bacterial flora in the intestine through adhesion, competitive exclusion, occupying and producing inhibitors, and have an important effect on local intestinal immunity.


    1. Lactic acid bacteria adhesion and colonization mechanism

        Adhesion is the first step in colonization. It enables lactic acid bacteria to expand the flora and avoid the clearance of intestinal fluids and intestinal peristalsis. In 1982 Kleeman and Klaenhammer found that lactic acid bacteria have two different adhesion mechanisms: It is a non-specific system that requires calcium, and the other is a calcium-independent system. There are two types of lactic acid bacteria in the calcium-independent system that are involved in the adhesion of lactic acid bacteria. One component is an anti-protease (associated with the surface of the bacteria); the other is Heat-stable extracellular proteins are sensitive to proteases, while Bifidobacteria are different, and their adhesion is assisted by a protein-like adhesion promoting factor in the bacterial surface or in the supernatant of Bifidobacterium cultures. It appears to be specific and adheres to the intestinal mucosal surface through filamentous components.

        Lactobacillus colonization is the process of adhesion. In general, after the baby is born, the lactic acid bacteria begin to colonize. This process is influenced by the age of the intestine, diet type and food composition. There are many interactions between various microorganisms, and their number depends on their respective activities. Various microorganisms secrete special substances to inhibit the growth of other strains (such as bacteriocins, organic acids, hydrogen peroxide, diacetyl, short chains). Fatty acids, etc.) A portion of the lactic acid bacteria in the intestinal tract is not affected by externally active strains and has a self-balancing normative system. Then lactic acid bacteria rapidly expanded, gradually forming dominant bacteria, resulting in a variety of inhibitors, a wide range of antibacterial activity, and repelling pathogenic bacteria (and depletion of nutrients) and inhibiting colonization by occupying epithelial cell receptors. Lactic acid bacteria maintain their quantitative stability by adsorbing to mucosal epithelial cells (using specific binding), including adsorption on the surface and membrane receptors, degrading sticky proteins and using this endogenous nutrients; there are also many substances that affect lactic acid bacteria Colonization, such as: lysozyme, hormones, antibiotics, etc.


    2. Lactic acid bacteria and cellular immunity

        Many studies have shown that lactic acid bacteria can interfere with cellular immunity, and lactic acid bacteria and bifidobacteria can block the invasion and adhesion of many microorganisms (sterile inhibition). Oral lactic acid bacteria or bifidobacterium can stimulate the body to produce non-specific immunity. Some strains of lactic acid bacteria: Lactobacillus rhamnosus (ATCC.53103), Lactobacillus plantarum (VTT), Lactobacillus (ARH74), Bifidobacterium subspecies are tumor necrosis factor-α (TNF-α) and IL-6 Some of the powerful inducers can stimulate the production of IL-10 to enhance immunity. Lactobacillus casei and Lactobacillus bulgaricus can activate macrophage function and stimulate the body to produce an immune response. It also enhances the immune system through the enhancement of the activity of macrophages, T cells, and NK cells; the activation of macrophages, NK cells, and T cells is beneficial to the enhancement of lymphocyte immunity in peripheral blood vessels and regional lymph nodes. T helper cells, The increase of NK cells can reduce inhibitory T cells. Lactobacillus acidophilus adsorbed on human body has antibacterial activity. The strain can be adsorbed on differentiated intestinal cells, and it can also resist Helicobacter pylori in vitro and kill invading bacteria.


    3. Lactic acid bacteria and humoral immunity

        Lactobacillus stimulates cell proliferation of SIgA produced by the body, which in turn raises the level of SIgA, which can prompt the system to generate an immune response to rotavirus, neutralize toxins, alleviate rotavirus-induced diarrhea, acute gastroenteritis, anorexia, and atopic dermatitis Symptoms such as Crohn's disease.

          In conclusion, the role of lactic acid bacteria and their products is similar to that of adjuvants, specifically the induction of interferon production, the promotion of cell division, humoral and cellular immunity.


    4. Probiotics in the gastrointestinal tract

        Probiotics are derived from the Greek "Probiotic" and in the human intestinal tract are mainly Bacteroides, Bifidobacteria, Lactobacillus, Streptococcus, etc. They prevent the colonization of pathogenic bacteria and have effects on nutrition, metabolism, immunity, etc. . The probiotic effect of lactic acid bacteria is mainly manifested in:
    (1) Treatment of intestinal disorders and maintenance of intestinal flora balance. Lactic acid bacteria produce large amounts of organic acids, hydrogen peroxide, enzymes, and bacteriocins. It inhibits the colonization and colonization of pathogens, promotes peristalsis and maintains normal physiological functions of the intestine.
    (2) Anti-tumor effect. Lactic acid bacteria are metabolized and inhibit the production of carcinogens and the proliferation of cancer cells. The bacillus bulgaricus has potential anti-tumor properties that can reduce the concentration of β-glucosidase and azoreductase and reduce the canceration rate.
    (3) Nutritional effects. Lactic acid produced by lactic acid bacteria can increase the absorption and utilization of calcium, phosphorus, iron and vitamin D. The galactose produced by the decomposition of lactose is a component that constitutes cerebrosides in the brain's nervous system and is closely related to the rapid growth of the brain after birth in infants.
    (4) Lower cholesterol. Lactic acid bacteria have the effect of inhibiting cholesterol synthesis. Lactic acid bacteria can better absorb cholesterol. Through metabolism, cholesterol is converted into bile acid and bile acid and excreted. Lactic acid bacteria and bifidobacteria can reduce cholesterol in the small intestine by digesting, absorbing, and degrading cholesterol and bile acids.
    (5) Anti-radiation effect. After oral administration of lactobacillus and bifidobacteria, the animals survived longer than the control group. Lactic acid bacteria can effectively protect the hematopoietic system and have an antimutagenic effect.
    (6) Other effects. Lactobacillus can detoxify the sugar by metabolically degrading sucrose and lowering pH. Lactic acid bacteria can degrade the aflatoxins and release their toxicity. When Lactobacillus delbrueckii and Mycobacterium enzyme (aflatoxin-producing bacteria) are cultured together, 45% to 55% of aflatoxins can be decomposed. The mechanism is that the fermentation product (acid) of lactic acid bacteria has the ability to degrade aflatoxin, and the lactic acid bacteria can inhibit the growth of the mold (via pH drop, competitive inhibition).


    5. Research and development of the prospects of gastrointestinal health products

        Lactic acid bacteria and other probiotics are one of the hot topics in biotechnology in the world today. Existing lactic acid bacteria and other probiotics and prebiotics products will certainly be popularized, popularized, and diversified. Humans will use the ecological system for the study of zoonotic animals, and use them. The interaction between animal research probiotics and related physiological components in the body will also have new advances and breakthroughs in the fields of bacterial and mucosal physiological changes, probiotics and mucosal immunity, engineering bacterial technology, in vivo labeling technology, and immunological detection technology. 

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