Sensitivity of Mouse Small Intestinal Immune Tissue Architecture

The different regions of the small intestinal lymphoid tissues may have developed a different immuno‐cytohistological structures with a different sensitivity in response to different intralumenal contents. However, the distribution and density of immune cell subsets, lymphatics, and their spatiotemporal relationship within or among Peyer’s Patches (PP), the major lymphoid immune tissues from proximal to distal ends of the small intestine, have not been clearly documented. The jejunal (Jej), mid‐segmental (Mid, Btw. Jej & Ile), and ileal (Ile) PPs in C57BL/6 mice were isolated, frozen‐sectioned, and immunohistochemistrico‐stained for the imaging analysis and comparison on the distribution, density, area, and size of immune cells, lymphatics, and their spatiotemporal relations between the peripheral and interfollicular regions within or among the different PPs. Results 1. Density of CD4+cells in the interfollicular regions (IFR) were significantly higher than those in the peripheral regions (PR) within each PP. 2. Total density of CD4+ or MHCII+ cells in MidPP were significantly higher than those in the JejPP. 3. The total density of CD8+cells in MidPP or CD68+cells in IlePP were significantly higher than those in the JejPP. 4. Total lymphatic area, density, or size in MidPP were significantly larger than those in JejPP. 5. Lymphatic area in IFR of MidPP or its density in IFR of MidPPs or IlePPs were significantly larger than those in the PR of the corresponding PPs. 6. Branched villi‐lacteals & their subsequent submucous lymphatic network wrapped by a higher density of CD4+ & MHCII+ cells directly form a specialized histo‐architecture, branched villi‐Lv‐PP complex for immune recognition/differentiation in mouse small intestine. The histo‐morphological architectures of mouse small intestinal immune tissues infrastructure its sensitivity as an immune‐surveillance sensor, facilitating its sensibility. This study provides a necessary foundation for understanding immune‐related intestinal dysfunctions and diseases.