From:  Mechanisms of action and health benefits of probiotics: a comprehensive review

 Mechanisms of action of probiotics to improve host immunity.

Antimicrobial activityBarrier functionsImmunomodulation
Changing luminal pH
Secreting antimicrobial peptides
Inhibit microbial invasion
Blocking microbial adhesion
Increased mucus production
Increased barrier stability
Epithelial cells
Dendritic cells
Macrophages
B cells & T cells