13497 IUPAC Gold Book - natural autoantibodies 10.1351/goldbook.13497 13497 current initialism: NAA 1 Part of the naturally occurring repertoire of polyreactive antibodies that bind to autoantigens with low affinity. They are mainly of immunoglobulin M (IgM) isotype and produced by CD5+ B lymphocytes. Natural antibodies and their producing cells may have a physiological role in the following processes: (i) first line of protection against external invaders, (ii) elimination of degraded autoantigens and senescent cells, and (iii) tolerization (see tolerance) of T cells by presenting autoantigens, thereby in protecting from development of pathological autoimmunity. In contrast, natural autoantibodies may become pathogenic in clonal B cell disorders, e.g., monoclonal anti-I antibodies in cold agglutinin disease cause autoimmune hemolytic anemia. CD5+ B lymphocytes https://goldbook.iupac.org//terms/view/12975 T cells https://goldbook.iupac.org//terms/view/13724 autoantigens https://goldbook.iupac.org//terms/view/12914 autoimmune hemolytic anemia https://goldbook.iupac.org//terms/view/12920 autoimmunity https://goldbook.iupac.org//terms/view/12925 immunoglobulin M (IgM) https://goldbook.iupac.org//terms/view/13293 isotype https://goldbook.iupac.org//terms/view/13347 tolerance https://goldbook.iupac.org//terms/view/13302 PAC, 2012, 84, 1113. 'IUPAC glossary of terms used in immunotoxicology (IUPAC Recommendations 2012)' on page 1218 (https://doi.org/10.1351/PAC-REC-11-06-03) https://goldbook.iupac.org/terms/view/13497/html https://goldbook.iupac.org/terms/view/13497/json https://goldbook.iupac.org/terms/view/13497/plain Citation: 'natural autoantibodies' 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.13497 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. 2026-07-14T03:11:45+00:00