Probiotics for immune system
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Probiotics and Their Impact on the Immune System
Introduction to Probiotics and Immune System Modulation
Probiotics are live microorganisms that, when administered in adequate amounts, confer health benefits to the host, including modulation of the immune system. The interaction between probiotics and the immune system is complex and involves various mechanisms that enhance immune responses and maintain immune homeostasis 12.
Mechanisms of Immune Modulation by Probiotics
Interaction with Intestinal Immune Cells
Probiotics interact with intestinal immune cells and commensal microflora to modulate specific immune functions. This interaction helps maintain a balance between immune tolerance and immunogenicity, which is crucial for a healthy immune system . Probiotics can stimulate immune cells such as macrophages, natural killer (NK) cells, and cytotoxic T-lymphocytes, leading to the release of various cytokines in a strain-specific and dose-dependent manner .
Enhancement of Gut Mucosal Immunity
Probiotics can improve the gut mucosal immune system by increasing the number of IgA+ cells and cytokine-producing cells in the intestine. This enhancement helps build a healthy intestinal mucosa protective layer, which is essential for preventing the colonization of pathogenic bacteria 56.
Clinical Evidence of Probiotics' Immune Benefits
Reduction in Upper Respiratory Infections
Several studies have demonstrated that probiotic supplementation can reduce the incidence of upper respiratory infections. For instance, a study involving adult volunteers who frequently contracted the common cold showed that probiotic consumption significantly reduced the incidence of upper respiratory infections and flu-like symptoms. This effect was associated with higher levels of serum IFN-γ and gut sIgA, indicating an enhanced immune response .
Impact on Inflammatory and Autoimmune Disorders
Probiotics have also been shown to impact inflammatory and autoimmune disorders. Randomized controlled trials have indicated that probiotics can improve gastrointestinal symptoms and reduce multiorgan inflammation in conditions such as rheumatoid arthritis, ulcerative colitis, and multiple sclerosis. These benefits are linked to the modulation of gut microbes and their metabolic pathways .
Limited Effects in Healthy Adults
However, the effects of probiotics on immune and inflammatory markers in healthy adults are less pronounced. A systematic review concluded that while probiotics can increase certain immune parameters like NK cells and lymphocytes, the overall impact on immune and inflammatory markers in healthy adults is limited and variable .
Probiotics in Viral Respiratory Tract Infections
Probiotics have been investigated for their role in reducing the risk and severity of viral respiratory tract infections (RTIs). Although the exact mechanisms remain unclear, specific probiotic strains have shown promise in pre-clinical models by stimulating the immune system and inhibiting viral replication. Clinical studies have yielded variable results, but meta-analyses suggest that probiotics could be beneficial in managing upper respiratory illnesses .
Conclusion
Probiotics offer a promising approach to enhancing immune system functions through various mechanisms, including the modulation of gut microbiota and stimulation of immune cells. While they have shown significant benefits in reducing upper respiratory infections and managing inflammatory and autoimmune disorders, their effects in healthy adults are less consistent. Further research is needed to fully understand the mechanisms and optimize the use of probiotics for immune health.
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