Lipopolysaccharides from Escherichia coli O111:B4 are key components of the outer membrane of Gram-negative bacteria. As a smooth-type LPS, they consist of lipid A, an R3-type core oligosaccharide, and an O-specific polysaccharide. These LPS molecules exhibit high immunogenicity, can trigger strong immune responses and gastric disorders by activating the TLR-4 receptor on immune cells, and help maintain the structural integrity of the bacterial outer membrane while protecting against bile salts and lipid-based antibiotics. They are widely used to establish inflammation-related disease models, such as chronic obstructive pulmonary disease (COPD) and acute respiratory distress syndrome (ARDS).