**7. How does gut interaction affect health?**

There is a substantial relationship between the intestinal barrier, the gut microbiota, and immune system cells. Increased epithelial permeability, often known as "leaky gut," permits bacteria, antigens, and toxins from the lumen to the lamina propria to enter the bloodstream, which triggers both local and systemic immune responses. The symbiotic relationship between the gut microbiota and the immune system may be disrupted by an impaired intestinal barrier function, which has been linked to the advancement of illnesses and disorders such as inflammatory bowel disease and irritability. Based on their potential effects, gut bacteria can be categorized

### **Figure 1.**

*Anatomical structure and composition of the gut barrier. In order of importance, there are four types of barriers: Microbiota barrier, chemical barrier, physical barrier, and immune barrier. Microorganisms, IgA, and antibacterial peptides make up the chemical barrier. It consists of IECs, goblet cells (synthesis of mucins), Paneth cells (synthesis of AMPs), and intestinal stem cells. There are T cells, B cells, macrophages, dendritic cells, and mast cells that form the immune barrier. In this image, the real arrow indicates the route by which SCFAs affect immune cells, whereas the dotted arrow indicates a possible route not described [17].*

into three categories: Lactobacilli and bifidobacteria; potentially dangerous bacteria, such as some clostridia species and other commensal bacteria, such as Bacteroides, which can have both positive and negative characteristics (**Figure 1**) [18].
