BACKGROUND: Oral immunization has numerous advantages over parenteral 
administrations. In addition to ease administration, more effective pathogen 
elimination on the mucosa before spreading into the blood circulation, 
constitutes the main benefit. This is particularly true for pathogens that enter 
the body through the oral route. On the other hand, it is the most challenging 
administration route for peptides, proteins and recombinant antigens due to 
gastrointestinal (GI) tract, numerous barriers including the harsh environment 
and the inherent weak immunogenicity. In addition to the adjuvant properties, 
polymeric particles arise as the most promising strategy to overcome poor 
antigen bioavailability/ stability upon oral administration. The Peyer's patches 
have been considered an important structure of the gut associate lymphoid tissue 
(GALT) for the initiation of the immune response towards particulate oral 
antigens.
OBJECTIVE: The transport mechanism of both, nano and microparticles across 
intestinal mucosa, particularly throughout Peyer's patches, is discussed in this 
review.
CONCLUSION: We provide a short and concise update (last decade) focused on the 
importance of particle physicochemical properties, M-cell ligands and 
size-dependent transport and intracellular fate concerning Peyer's patches 
targeted oral vaccination.