**3.1 LP of the intestinal mucosa**

The LP of the intestinal mucosa is located below the intestinal epithelial cells and includes various cell types, including Ig-derived plasma cells, T cells, dendritic cells, macrophages, and various cytokines [46]. Under normal conditions, the LP of the intestinal mucosa exhibits high levels of TGF-β [47] and IL-10 [48], which promotes antigen-activated B-cell isoforms. The pathogen enters the LP of the intestinal mucosa from the intestines. The pathogen is recognised by the immune system, and it stimulates B cells to undergo isotype switching to secrete IgA, IgG, and IgM. In a study, rats were administered inactivated *Entamoeba histolytica* through feeding, and IgA, IgG, and IgM were detected in serum and faeces on postfeeding days 2, 4, 6, 8, and 10. IgG and IgM expression in rat serum increased, and IgG and IgA expression in faeces also increased [49].
