Figure 1

Helper Th2 cells play a central role in allergic asthma and could be targeted through individual allergic immune processes. (1) Allergen handling and presentation by activated APC to naïve CD4+ T cells induces their activation. (2) Activated naïve CD4+ T cells differentiate to Th2 cells, or (3) possibly to other types of helper T cells e.g. Th1, Th17 or Treg cells. (4) Secondary exposure to allergen leads to Th2 cell activation, (5) as well as their migration into the lungs. (6) Activated Th2 cell-mediated asthma is caused in part by the secretion of interleukins e.g. IL-4, IL-5 and IL-13. These cytokines stimulate B cell activation and IgE secretion. Th2 cell cytokines and IgE activate cells of the innate immune system e.g. eosinophils, mast cells, etc. causing the release of vasoactive, pro-inflammatory mediators, smooth muscle contraction, mucus hypersecretion, oedema and, eventually, airway remodelling. (7) Homeostasis and survival of memory T cells in the lymph nodes and lungs perpetuates disease. Interruption of these molecular and cellular targets may reduce symptoms and pathological consequences of allergic asthma.