Probiotics play a crucial role in supporting and modulating the immune system, which is essential for defending against pathogens and maintaining overall health. The gut microbiome interacts closely with the immune system, influencing its development, function and response to infections.
1. Modulation of Gut Microbiota
Probiotics help maintain a balanced and diverse gut microbiome by promoting the growth of beneficial bacteria and inhibiting the growth of harmful bacteria. A balanced gut microbiome is essential for a healthy immune system as it supports the development and function of immune cells.
2. Enhancement of Gut Barrier Function
Probiotics help strengthen the gut barrier, also known as the intestinal epithelial barrier, which serves as the first line of defense against pathogens and harmful substances. A healthy gut barrier prevents the entry of pathogens and toxins into the bloodstream, reducing the risk of infections and inflammation.
3. Regulation of Immune Cells and Responses
Probiotics can stimulate the activity and function of immune cells, including macrophages, dendritic cells, and T and B lymphocytes, which play crucial roles in identifying and eliminating pathogens.
Probiotics produce anti-inflammatory compounds, such as short-chain fatty acids (SCFAs) and certain metabolites, which help reduce inflammation and regulate immune responses to prevent excessive inflammation and tissue damage.
4. Competition with Pathogenic Bacteria
Probiotics compete with pathogenic bacteria for nutrients and colonisation sites in the gut, preventing the overgrowth of harmful bacteria and reducing the risk of infections.
5. Production of Antimicrobial Substances
Some probiotic strains produce antimicrobial substances, such as bacteriocins and hydrogen peroxide, which have direct antimicrobial activity against pathogenic bacteria, viruses, and fungi, supporting a healthier gut environment.
6. Regulation of Immune Signalling Pathways
Probiotics can modulate immune signalling pathways, such as the NF-kB pathway and Toll-like receptor (TLR) signalling, to enhance immune responses against infections and promote immune tolerance to prevent autoimmune reactions.