Phosphoinositide 3-kinase δ (p110δ) was shown to play a crucial role in the development, differentiation and antigen receptor-induced proliferation of mature B cells [47, 48], and inhibition of p110δ attenuates allergic airway inflammation and AHR in a murine asthma model [48, 49]. The gene discussed is PIK3CD; the disease is asthma.