Recent studies suggest that human regulatory T (T reg) cells protect against the development of allergic and asthmatic disease and that their function is impaired during active disease. Two new studies contribute to our understanding of the role that T reg cells play in the control of allergic airway disease in mice. However, these studies also highlight several outstanding questions in the field.
Medical Research Council and Asthma UK Centre for Allergic Mechanisms in Asthma, King's College London, London SE1 9RT, UK. C.M.H.catherine.hawrylowicz@kcl.ac.uk
