Lipopolysaccharides on the Intestinal Mucosal Immune Barrier

10 The small intestinal villus is covered with a thick layer of mucus that is secreted by goblet 11 cells and functions primarily to first barrier from damage by toxic substance. Recent studies 12 showed that goblet cells and mucins involved in complex immune function. Lipopolysaccharide 13 (LPS) is widespread in the housing of livestock, which can induce bacterial infection symptoms 14 and immunological stress within a short of time. Therefore, we aimed to study the effects of 15 long-term exposure to different doses of LPS on intestinal mucus layer and immune barrier. The 16 result showed that mucus layer thickness and goblet cell functions were significantly increased 17 after low doses of LPS. The intestinal mucosal barrier can block the bacteria of the lumen, but 18 LPS can penetrate this barrier into the blood, putting the body in a state of chronic low-grade 19 inflammation and reducing the body’s immune function. However, after long-term exposure to 20 high doses of LPS, a large number of lysosomes in goblet cells caused loss of function, and mucus 21 layer thickness was significantly decreased. A large amount of LPS stuck to the mucus, leading to 22 normal LPS and inflammatory cytokines level of plasma. The intestinal tissue morphology was 23 damaged, and a number of immune cells were necrosis in the intestine. Collectively, long-term 24 exposure to low doses of LPS lead to chronic low-grade inflammation in the body. Long-term 25 exposure to high doses of LPS can be directly linked to the severity of the immunosuppression in 26 the body. 27 Keyword: lipopolysaccharides; mucin; ileum; MUC2; mucosal barrier; mouse 28