https://doi.org/10.1351/goldbook.13189
Lymphoid cells and tissues lining the mucosa that seem to serve as the first point of antigen contact via this route, including Peyer’s patches, the appendix, tonsils, adenoids, and mesenteric lymph nodes.
Note: Large aggregates of GALT have distinct B-cell follicles and T-cell areas. Antigen-presenting accessory cells are also present.