The immune system doesn’t only fight invaders once they enter the body, it relies heavily on barriers: physical, chemical, and microbial. Barriers are crucial for preventing infections before immune cells need to act. 

𝗣𝗵𝘆𝘀𝗶𝗰𝗮𝗹 𝗮𝗻𝗱 𝗔𝗻𝗮𝘁𝗼𝗺𝗶𝗰𝗮𝗹 𝗕𝗮𝗿𝗿𝗶𝗲𝗿𝘀 
𝘚𝘬𝘪𝘯: The outermost layer provides a tough, largely impermeable barrier. Tight junctions in the epidermis, keratin, and constant cell turnover prevent microbial entry [1]. 
𝘔𝘶𝘤𝘰𝘴𝘢𝘭 𝘴𝘶𝘳𝘧𝘢𝘤𝘦𝘴: Respiratory, gastrointestinal, and urogenital tracts are lined with epithelial cells, mucus that trap or expel pathogens. 
𝘔𝘦𝘤𝘩𝘢𝘯𝘪𝘤𝘢𝘭 𝘳𝘦𝘮𝘰𝘷𝘢𝘭: Cilia in the airways and peristalsis in the gut help push away invaders. 

𝗖𝗵𝗲𝗺𝗶𝗰𝗮𝗹 𝗕𝗮𝗿𝗿𝗶𝗲𝗿𝘀 
𝘈𝘤𝘪𝘥𝘪𝘤 𝘦𝘯𝘷𝘪𝘳𝘰𝘯𝘮𝘦𝘯𝘵𝘴: Gastric acid in the stomach destroys many ingested microbes. 
𝘈𝘯𝘵𝘪𝘮𝘪𝘤𝘳𝘰𝘣𝘪𝘢𝘭 𝘱𝘦𝘱𝘵𝘪𝘥𝘦𝘴: Defensins, cathelicidins, and lysozyme are secreted by epithelial cells and neutrophils to directly kill pathogens. 
𝘚𝘦𝘤𝘳𝘦𝘵𝘦𝘥 𝘐𝘨𝘈: Provides immune surveillance at mucosal surfaces, preventing adhesion and invasion by microbes [2]. 

𝗠𝗶𝗰𝗿𝗼𝗯𝗶𝗮𝗹 𝗕𝗮𝗿𝗿𝗶𝗲𝗿𝘀 
𝘊𝘰𝘮𝘮𝘦𝘯𝘴𝘢𝘭 𝘮𝘪𝘤𝘳𝘰𝘣𝘪𝘰𝘵𝘢: Skin, gut, and mucosal microbes compete with pathogens for nutrients and space, produce inhibitory molecules, and train local immune responses [2]. 

𝗚𝗲𝗿𝗺𝗮𝗻 𝗖𝗼𝗻𝘁𝗿𝗶𝗯𝘂𝘁𝗶𝗼𝗻𝘀 
Mathias Hornef (University of Aachen) studies intestinal epithelial defenses, microbial interactions, and how neonatal exposure shapes barrier immunity [3]. 
Stefan F. Martin (Freiburg) investigates skin barrier immunity and the interaction of epithelial cells with immune cells during inflammation [4]. 
Maik Luu (University Hospital Würzburg): Explores how microbial metabolites, such as short-chain fatty acids, can enhance CAR-T and TCR immunotherapies, linking barrier microbiota to advanced immune interventions [5]. 

𝗙𝗮𝘀𝗰𝗶𝗻𝗮𝘁𝗶𝗼𝗻 & 𝗦𝗽𝗲𝗰𝘂𝗹𝗮𝘁𝗶𝗼𝗻 
𝘚𝘱𝘦𝘤𝘶𝘭𝘢𝘵𝘪𝘷𝘦 𝘩𝘺𝘱𝘰𝘵𝘩𝘦𝘴𝘪𝘴: Could training or modulating these barriers (microbiome diversity, antimicrobial peptide expression) serve as a preventive immunotherapy? ->[5] 

Stay tuned for 𝗗𝗮𝘆 𝟵: 𝗜𝗻𝗳𝗹𝗮𝗺𝗺𝗮𝘁𝗶𝗼𝗻 𝟭𝟬𝟭 

𝗥𝗲𝗳𝗲𝗿𝗲𝗻𝗰𝗲𝘀 
1. DOI: 10.1038/nri3228 
2. DOI: 10.1016/j.immuni.2017.04.008 
3. DOI: 10.1111/imm.13149 
4. DOI: 10.5414/ALX01274E 
5. https://lnkd.in/eqE8SKkq 

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