Innate Th2-type immune responses and the natural helper cell, a newly identified lymphocyte populationKoyasu, Shigeo; Moro, KazuyoCurrent Opinion in Allergy and Clinical Immunology: April 2011 - Volume 11 - Issue 2 - p 109–114 doi: 10.1097/ACI.0b013e3283448808 Pediatric asthma and development of atopy: Edited by Carlos E. Baena-Cagnani and Leonard B. Bacharier Abstract Author Information Purpose of review We discuss recent progress in the understanding of Th2 cytokines derived from innate cells involved in the pathophysiology of various allergic diseases. Recent findings Recent studies have identified a previously unrecognized lymphocyte population capable of producing Th2 cytokines in response to IL-25 and/or IL-33 independently of T or B cells. Summary Newly identified cells responsive to IL-25 and/or IL-33 include natural helper cells, MPPtype2, nuocytes and innate helper type 2 cells. These cells produce large amounts of Th2 cytokines, most notably IL-5 and IL-13, leading to eosinophilia and goblet cell hyperplasia and are critical for antihelminth reactions. IL-5 and IL-13 also play a role in pathophysiology of allergic diseases such as asthma and allergic diarrhea. There are similarities and differences between these newly identified cell populations. MPPtype2 cells can potentially differentiate to other myeloid cells, making this cell type distinct from the others. Natural helper cells constitutively produce Th2 cytokines, support the self-renewal of B1 cells and enhance IgA production. Unlike other innate Th2 producers, natural helper cells are present in fat-associated lymphoid clusters and likely play additional roles in the regulation of homeostasis in adipose tissues. Department of Microbiology and Immunology, Keio University School of Medicine, Tokyo, Japan Correspondence to Shigeo Koyasu, PhD, Department of Microbiology and Immunology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan Tel: +81 3 5363 3768; fax: +81 3 5361 7658; e-mail: firstname.lastname@example.org Copyright © 2011 Wolters Kluwer Health, Inc. All rights reserved.