The role of the T cell in asthma

Since the initial detection of TH2 cytokines in asthmatic airways, our understanding of the complexity of T-cell subtypes and flexibility and of the potential role of airway structural cells in the immunopathology of asthma has increased. Cytokines derived from airway epithelium, including IL-25, IL-33, and thymic stromal lymphopoietin, might be important drivers of TH2-type inflammation in asthma. The balance between effector TH2 cells and suppressive regulatory T cells is skewed toward a proinflammatory TH2 response in atopy and asthma, and there is much interest in how to redress this equilibrium. Novel T-cell subsets, including TH17, TH9, and TH22, have been described, although their role in asthma remains unclear. Other T cells, including natural killer T cells, γδ T cells, and CD8 T cells, have also been implicated in asthma, although their importance remains to be confirmed. Therapeutic strategies aimed at TH2 cytokines are beginning to bear fruit in patients with asthma, although like many biologic agents, these might need specific targeting at subgroups of patients. Strategies directed specifically at the T cells are currently being evaluated, including novel forms of allergen immunotherapy. T cells remain an exciting potential target for new treatments in patients with asthma.