Our demonstration that IL-10 plays a pivotal role in controlling immunopathology driven lung inflammation in vivo and the further highlighting of Foxp3− effector T cells as main lymphocytes producing it is an important step in elucidating the mechanisms by which the fine balance between clearing virus and controlling immune responses is achieved in the respiratory tract, allowing normal gas exchange to be maintained in the face of viral attack. The gene discussed is IL10; the disease is inflammation.