The evolution of allergy immunotherapy

Objective: The objective of this review is to trace the evolution of the art and science of allergy immunotherapy (AIT). Data Sources: Original reports relating to the evolution of the concept of respiratory allergy and its specific treatment were identified by following references in journal articles, review articles, and allergy textbooks from the mid-20th century to the present. Study Selections: Studies highlighting substantial milestones in the evolution of the practice of allergy immunotherapy were included. Results: The story of AIT begins with the recognition of hay fever as a distinct entity and subsequent studies that established grass pollen as one of the causes. This knowledge led several investigators, most notable Leonard Noon and John Freeman who worked at St. Mary?s Hospital in London, to attempt to induce tolerance giving grass pollen extract by injection to their patients. After the publication of the work of Noon and Freeman in 1911, the practice of AIT spread rapidly and was applied to many other pollen allergens besides grass and for perennial rhinitis and asthma. The early studies were largely anecdotal, but over the past 60 to 70 years, studies of AIT have been conducted with increasingly sophisticated scientific methods. Nowadays, not only is the practice of AIT based on carefully conducted studies, but the underlying immunologic basis of allergy and the response to AIT have also been and still are being firmly established. Conclusion: Both the art and the science behind the practice of AIT have been established by a solid base of clinical and immunologic studies. ? 2020 American College of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved. ? Recognition of hay fever as a distinct entity coincided with the marked increase in the prevalence of allergic diseases in the latter part of the 19th century. This probably reflected the improving levels of hygiene and the trend toward urbanization. ? Allergy immunotherapy (AIT) was practiced with a high level of enthusiasm for more than 4 decades before randomized, controlled studies scientifically established its efficacy. In the 6 decades since, well-designed studies have established its efficacy in seasonal and perennial allergic rhinitis, asthma, and Hymenoptera venom sensitivity. ? Studies have also established the principal humoral response to AIT to be the generation of specific immunoglobulin G4, whereas the cellular response is characterized early by the generation of a variety of regulatory T cells and later by an immune deviation from TH2 to