Gut mucosal immunostimulation by lactic acid bacteria

Area of Science:

• Immunology
• Microbiology
• Gastroenterology

Background:

• Lactic acid bacteria (LAB) offer health benefits, but their role in activating the gut mucosal immune system and their adjuvant potential remain unclear.
• The specific mechanisms and whether all LAB strains possess adjuvant properties are not fully understood.

Purpose of the Study:

• To investigate the influence of oral administration of various LAB genera on the gut mucosal immune system.
• To determine if different LAB strains stimulate specific, non-specific (inflammatory), or both immune responses.
• To assess the immunoadjuvant capacity of selected LAB strains.

Main Methods:

• Oral administration of diverse LAB genera including Lactobacillus casei, L. acidophilus, L. rhamnosus, L. delbrueckii subsp. bulgaricus, L. plantarum, Lactococcus lactis, and Streptococcus thermophilus.
• Evaluation of stimulation of specific and non-specific immune responses.
• Quantification of IgA-producing cells in the lamina propria and assessment of CD4+ and CD8+ T cell populations.

Main Results:

• All tested LAB increased IgA-producing cells in the small intestine lamina propria in a dose-dependent manner.
• IgA+ cell increase was not always linked to CD4+ T cell elevation, suggesting some LAB promote B cell activation only.
• Most LAB increased inflammatory response cells, while CD8+ T cells generally decreased or remained unaffected, except for L. plantarum at low doses.

Conclusions:

• The immunoadjuvant capacity varies significantly among LAB strains, indicating that not all LAB can serve as effective oral adjuvants.
• The beneficial effects of LAB cannot be generalized across genera or species; strain-specific properties are crucial.
• Careful selection of LAB strains is essential for optimizing their use as gut mucosal adjuvants.