Th2 cells in rapid immune responses and protective avoidance reactions

Abstract Type 2 helper cells (Th2 cells) differentiate from CD4 helper T cells under the influence of IL‐4 and conventional or monocyte‐derived CD11b + dendritic cells. Th2 cells are capable of generating IL‐4, IL‐5, and IL‐13, as well as evoking immunoglobulin class‐switch to IgE. Three types of rapid immune responses are Th2 cell‐dependent: (1) mast cell‐IgE mediated allergic reactions, (2) Th2 cell‐derived cytokine‐mediated reactions that complement allergic reactions and protect the host from toxins, xenobiotics, environmental irritants, and helminthic parasites, and (3) IgE‐stimulated mast cell‐derived cysteinyl‐leukotriene mediated avoidance of toxins. The contributions of Th2 cell‐derived cytokines to eosinophilia (IL‐5), IgE class‐switch, and epithelial barrier activation, mucous secretion, and metaplasia (IL‐4 and IL‐13) in asthma, allergic rhinitis with polyps and atopic dermatitis have led to anti‐cytokine monoclonal antibody treatments. Anti‐IL‐5 neutralizing monoclonal antibody in asthma and anti‐IL‐4/IL‐13 receptor neutralizing monoclonal antibody in asthma and atopic dermatitis are proven successful therapies in appropriately selected patients who are not sufficiently improved by conventional treatments.