New nomenclature of allergic diseases and hypersensitivity reactions

Abstract

The review presents a modern view on the mechanisms of initiation and development of hypersensitivity reactions in response to external triggers based on the new nomenclature of allergic diseases proposed in 2023 by EAACI. The new concept of hypersensitivity is considered in detail, which systematizes previous classifications and summarizes newly obtained data on the etiology and mechanisms of development of inflammatory reactions in comparison with various variants of the immune response, based on the concept of phenotypes and endotypes of the disease. The modern concept of allergic reactions includes several types - associated with antibody formation (I-III), cell-mediated (IVa-c) and the Pichler concept, tissue-dependent, caused by defects in the epithelial barrier and metabolically induced immune dysregulation (V-VI), as well as a direct immunoinflammatory reaction to chemicals (VII). In the updated classification of allergic reactions, the adaptive and innate immune responses take a part in the initiation and effector phase of hypersensitivity reactions. The role of regulatory and effector subpopulations of lymphocytes and ILCs in various types of hypersensitivity is outlined. The leading role of epithelial barrier dysfunction in many allergic diseases, as well as the influence of viral infection on their course, is noted. The significance of metabolic dysregulation and its impact on the immune response is indicated. From the updated nomenclature of allergic reactions, it follows that several pathophysiological mechanisms may underlie the development of the same disease. It is interesting that most cellular and humoral factors are involved in various mechanisms of hypersensitivity, which once again confirms the biological universality of the immune response. As a wide range of people become familiar with the new concept and clinical and experimental data accumulate, the updated classification of hypersensitivity types will contribute to a theoretically sound, correct practical approach to the prevention of allergic diseases, improving their diagnosis and treatment.