Immunopathogenesis of Allergic Asthma: More Than the Th2 Hypothesis

Review  Open Access

|    Allergy Asthma Immunol Res. 2013 Jul;5(4):189-196. English. Published online 2013 April 12.  http://dx.doi.org/10.4168/aair.2013.5.4.189  Copyright © 2013 The Korean Academy of Asthma, Allergy and Clinical Immunology • The Korean Academy of Pediatric Allergy and Respiratory Disease Immunopathogenesis of Allergic Asthma: More Than the Th2 Hypothesis You-Me Kim, You-Sun Kim, Seong Gyu Jeon and Yoon-Keun Kim Department of Life Science, Pohang University of Science and Technology (POSTECH), Pohang, Korea.  Correspondence to: Yoon-Keun Kim, MD, PhD, POSTECH Biotech Center, 55 Jigok-ro, Nam-gu, Pohang 790-834, Korea. Tel: +82-54-279-2125; Fax: +82-54-279-8449; Email: juinea@postech.ac.kr  Received September 15, 2012; Accepted October 10, 2012. This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Abstract Asthma is a chronic obstructive airway disease that involves inflammation of the respiratory tract. Biological contaminants in indoor air can induce innate and adaptive immune responses and inflammation, resulting in asthma pathology. Epidemiologic surveys indicate that the prevalence of asthma is higher in developed countries than in developing countries. The prevalence of asthma in Korea has increased during the last several decades. This increase may be related to changes in housing styles, which result in increased levels of indoor biological contaminants, such as house dust mite-derived allergens and bacterial products such as endotoxin. Different types of inflammation are observed in those suffering from mild-to-moderate asthma compared to those experiencing severe asthma, involving markedly different patterns of inflammatory cells and mediators. As described in this review, these inflammatory profiles are largely determined by the involvement of different T helper cell subsets, which orchestrate the recruitment and activation of inflammatory cells. It is becoming clear that T helper cells other than Th2 cells are involved in the pathogenesis of asthma; specifically, both Th1 and Th17 cells are crucial for the development of neutrophilic inflammation in the airways, which is related to corticosteroid resistance. Development of therapeutics that suppress these immune and inflammatory cells may provide useful asthma treatments in the future. Keywords: Allergic asthma, endotoxin, immunopathogenesis, T helper cell.