The article discusses the role of mucins in the mucosal barrier to infection, focusing on their structure, biosynthesis, and function. Mucins are glycoproteins secreted by mucosal epithelial cells, forming a physical barrier and providing a matrix for antimicrobial molecules. They are crucial in accommodating commensal flora and limiting infectious diseases. The article highlights the interplay between mucins and the immune system, both innate and adaptive, and how successful mucosal pathogens subvert or avoid the mucin barrier. Key points include: 1. **Mucin Structure and Biosynthesis**: Mucins are large, complex glycoproteins with O-linked carbohydrates. They form a gel that protects the epithelial cells and acts as a physical barrier. Mucin glycosylation is highly variable and can alter in response to infection and inflammation. 2. **Mucin Roles in Defense**: Mucins function as decoys for microbial adhesins, binding to them and preventing their attachment to the epithelial surface. They also have direct antimicrobial activities and can retain antimicrobial molecules in the mucosal environment. 3. **Subversion of the Mucin Barrier**: Pathogens use various strategies to break through the mucin barrier, including producing enzymes that degrade mucins and effective motility through mucus gels. Some pathogens avoid the mucin barrier by attaching to specific cells or disrupting tight junctions. 4. **Models for Study**: Various models, including cancer cell lines, organ cultures, and animal models, are used to study mucin-microbe interactions. However, differences in mucin glycosylation between species can complicate these studies. 5. **Conclusion**: Mucins are dynamic components of the mucosal barrier that interact with and respond to other elements of the immune system. Understanding their roles in host defense requires overcoming challenges in working with complex glycoproteins and developing more physiological experimental systems.The article discusses the role of mucins in the mucosal barrier to infection, focusing on their structure, biosynthesis, and function. Mucins are glycoproteins secreted by mucosal epithelial cells, forming a physical barrier and providing a matrix for antimicrobial molecules. They are crucial in accommodating commensal flora and limiting infectious diseases. The article highlights the interplay between mucins and the immune system, both innate and adaptive, and how successful mucosal pathogens subvert or avoid the mucin barrier. Key points include: 1. **Mucin Structure and Biosynthesis**: Mucins are large, complex glycoproteins with O-linked carbohydrates. They form a gel that protects the epithelial cells and acts as a physical barrier. Mucin glycosylation is highly variable and can alter in response to infection and inflammation. 2. **Mucin Roles in Defense**: Mucins function as decoys for microbial adhesins, binding to them and preventing their attachment to the epithelial surface. They also have direct antimicrobial activities and can retain antimicrobial molecules in the mucosal environment. 3. **Subversion of the Mucin Barrier**: Pathogens use various strategies to break through the mucin barrier, including producing enzymes that degrade mucins and effective motility through mucus gels. Some pathogens avoid the mucin barrier by attaching to specific cells or disrupting tight junctions. 4. **Models for Study**: Various models, including cancer cell lines, organ cultures, and animal models, are used to study mucin-microbe interactions. However, differences in mucin glycosylation between species can complicate these studies. 5. **Conclusion**: Mucins are dynamic components of the mucosal barrier that interact with and respond to other elements of the immune system. Understanding their roles in host defense requires overcoming challenges in working with complex glycoproteins and developing more physiological experimental systems.