Table 1.

Components and characteristics of Peyer’s patches

Components	Characteristics	References
Follicle-associated epithelium (FAE)	- Specialized epithelial layer that overlies lymphoid follicles of PPs - Function as barrier between the intestinal lumen and PPs	[7]
Microfold (M) cells	- Specialized enterocytes, present in the FAE - Transport of luminal antigens to PPs - Low level of glycocalyx covering and flat apical surface for efficient interactions with particulate antigens - Binding the S-IgA for efficient capturing and transporting of luminal antigens - Expression of diverse glycan signatures on the apical membrane for recognition of certain bacteria or immune complexes - Presence of M cell pockets on the basolateral membrane for the migration of immune cells into the intraepithelial	[11, 18–23]
Subepithelial dome (SED)	- Areas located between the FAE and B cell follicles of PPs - Containing the high density of DCs - Direct interactions between M cells and DCs	[29–31]
Large B cell follicles	- Network of diverse populations of B cells - Antigen encounter - Complex interactions with T cells, DCs or FDCs - Initial activation of naïve B cells	[32]
Germinal centers (GCs)	- Clonal expansion and differentiation of B cells - Undergo SHM and CSR - Generation of IgA-secreting B cells	[32–35]
Small T cell zone	- Network of diverse populations of T cells - Delivering activation signals from CD4 + T cells to B cells	[32]
High endothelial venules (HEVs)	- Entry of lymphocytes to PPs - High expression of MADCAM-1, a ligand for α4β7 integrin, and CXCL13, a ligand for CXCR5 for B cell entry	[18]
Efferent lymphatics	- Leave effector cells generated in the PPs to MLN	[32]