What are the roles of probiotics in immune regulation?

1. Enhance immune defense function
Promoting immune cell activity: Probiotics such as lactobacilli and bifidobacteria can activate macrophages, natural killer (NK) cells, and dendritic cells, enhancing their ability to engulf and kill pathogens.
Increase Secretory IgA (sIgA): Probiotics stimulate intestinal mucosa to secrete sIgA, strengthen mucosal barrier function, and prevent pathogen adhesion and invasion.
Regulating cytokine secretion: Probiotics enhance their ability to clear viruses and intracellular pathogens by promoting the secretion of Th1 cytokines such as IFN - γ and IL-12.
2. Maintain immune tolerance and anti-inflammatory effects
Inhibiting excessive immune response: Probiotics can induce the differentiation of regulatory T cells (Tregs), secrete anti-inflammatory cytokines (such as IL-10, TGF - β), and alleviate excessive inflammatory response.
Relieve allergies and autoimmune diseases: Certain strains of bacteria (such as Lactobacillus rhamnosus GG strain) can reduce Th2 type reactions (such as IgE mediated allergic reactions) by regulating Th1/Th2 balance.
Improving intestinal barrier: By maintaining the integrity of tight junction proteins, reducing endotoxin (such as LPS) translocation, and lowering systemic inflammation.
3. Regulate the balance of gut microbiota
Competitive inhibition of pathogens: Probiotics occupy the intestinal niche, compete for nutrients, and secrete antibacterial substances (such as bacteriocins and short chain fatty acids) to inhibit the overgrowth of harmful bacteria.
Promote the production of short chain fatty acids (SCFAs): SCFAs such as butyric acid and propionic acid have anti-inflammatory effects and can nourish colon epithelial cells, enhancing barrier function.
4. The synergistic effect of systemic and local immunity
Regulation of gut lung axis/gut brain axis: The immune status of the gut affects distant organs (such as the lungs and nervous system) through circulating immune cells or metabolites, for example, certain probiotics can reduce the risk of respiratory infections.
Vaccine adjuvant effect: Some probiotics (such as Lactobacillus acidophilus) can enhance the immune response of vaccines.
5. Differentiated effects of specific bacterial strains
The effects of different probiotic strains may vary, for example:
Lactobacillus reuteri: Relieve infantile eczema.
Long Bifidobacterium BB536: Improves seasonal allergy symptoms.
Saccharomyces boulardii: Adjuvant treatment for antibiotic associated diarrhea