1 National Heart and Lung Institute, Imperial College London, London, England; Host Defence Unit, Department of Respiratory Medicine, Royal Brompton Hospital, Guy's and St Thomas' NHS Foundation Trust, London, England.
2 National Heart and Lung Institute, Imperial College London, London, England; Host Defence Unit, Department of Respiratory Medicine, Royal Brompton Hospital, Guy's and St Thomas' NHS Foundation Trust, London, England. Electronic address: m.loebinger@rbht.nhs.uk.