13498 IUPAC Gold Book - natural immunity 10.1351/goldbook.13498 13498 current 1 Host defense mechanisms that do not require prior exposure to antigen. Nonimmunological defense may involve the actions of macrophages and natural killer (NK) cells, mucocutaneous or integumental barriers, the action of cilia or microvilli, or physiological processes, e.g., urinary outflow, vascular perfusion of tissues, or the presence of native flora, which "outcompete" pathogens. Host defense https://goldbook.iupac.org/terms/view/13226 macrophages https://goldbook.iupac.org/terms/view/13424 natural killer (NK) cells https://goldbook.iupac.org/terms/view/13499 PAC, 2012, 84, 1113. 'IUPAC glossary of terms used in immunotoxicology (IUPAC Recommendations 2012)' on page 1219 (https://doi.org/10.1351/PAC-REC-11-06-03) https://goldbook.iupac.org/terms/view/13498/html https://goldbook.iupac.org/terms/view/13498/json https://goldbook.iupac.org/terms/view/13498/plain Citation: 'natural immunity' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351/goldbook.13498 The IUPAC Gold Book is licensed under Creative Commons Attribution-ShareAlike CC BY-SA 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) for individual terms. If you are interested in licensing the Gold Book for commercial use, please contact the IUPAC Executive Director at executivedirector@iupac.org . The International Union of Pure and Applied Chemistry (IUPAC) is continuously reviewing and, where needed, updating terms in the Compendium of Chemical Terminology (the IUPAC Gold Book). Users of these terms are encouraged to include the version of a term with its use and to check regularly for updates to term definitions that you are using. 2026-06-30T04:21:31+00:00